Entomologia Experimentalis et Applicata

Published by Wiley
Online ISSN: 1570-7458
Print ISSN: 0013-8703
Schematic of the experimental design performed to test the influence of Formica fusca on the horizontal transmission of either Nosema lymantriae or Vairimorpha disparis. The exposure periods (thick arrow) which always began at 10 dpi and the predation periods of F. fusca for each treatment group are indicated. Each group was set up in eight replicates. For further details refer to the text.
Mean (± SE) percent infection of Lymantria dispar test larvae feeding on foliage that was possibly contaminated with spores of Nosema lymantriae or Vairimorpha disparis following predation by Formica fusca on microsporidia-infected L. dispar larvae. Infection rate did not differ significantly between treatments with and without ants (U-test: P>0.05).
Influence of Formica fusca on the mean (± SE) percent infection of Lymantria dispar test larvae with (A) Nosema lymantriae or (B) Vairimorpha disparis, their recovery rates, and the proportions of recovered inoculated larvae. White bars represent the ‘no-ant’ control with short (10–15 dpi) and long (10–20 dpi) larval exposure period; gray bars represent treatments with short (10–15 dpi) and long (10–20 dpi) exposure period of L. dispar and with F. fusca workers present either 11–13 or 16–18 dpi. Formica fusca did not influence any dependent variable. For detailed statistical analysis see Table 3.
Transmission plays an integral part in the intimate relationship between a host insect and its pathogen that can be altered by abiotic or biotic factors. The latter include other pathogens, parasitoids, or predators. Ants are important species in food webs that act on various levels in a community structure. Their social behavior allows them to prey on and transport larger prey, or they can dismember the prey where it was found. Thereby they can also influence the horizontal transmission of a pathogen in its host's population. We tested the hypothesis that an ant species like Formica fusca L. (Hymenoptera: Formicidae) can affect the horizontal transmission of two microsporidian pathogens, Nosema lymantriae Weiser (Microsporidia: Nosematidae) and Vairimorpha disparis (Timofejeva) (Microsporidia: Burenellidae), infecting the gypsy moth, Lymantria dispar L. (Lepidoptera: Erebidae: Lymantriinae). Observational studies showed that uninfected and infected L. dispar larvae are potential prey items for F. fusca. Laboratory choice experiments led to the conclusion that F. fusca did not prefer L. dispar larvae infected with N. lymantriae and avoided L. dispar larvae infected with V. disparis over uninfected larvae when given the choice. Experiments carried out on small potted oak, Quercus petraea (Mattuschka) Liebl. (Fagaceae), saplings showed that predation of F. fusca on infected larvae did not significantly change the transmission of either microsporidian species to L. dispar test larvae. Microscopic examination indicated that F. fusca workers never became infected with N. lymantriae or V. disparis after feeding on infected prey.
Plant phenolics are generally thought to play significant roles in plant defense against herbivores and pathogens. Many plant taxa, including Solanaceae, are rich in phenolic compounds and some insect herbivores have been shown to acquire phenolics from their hosts to use them as protection against their natural enemies. Here we demonstrate that larvae of an insect specialist on Solanaceae, the tobacco hornworm, Manduca sexta L. (Lepidoptera: Sphingidae), acquire the plant phenolic chlorogenic acid (CA), and other caffeic acid derivatives as they feed on one of their hosts, Nicotiana attenuata L. (Solanaceae), and on artificial diet supplemented with CA. We test the hypothesis that larvae fed on CA-supplemented diet would have better resistance against bacterial infection than larvae fed on a standard CA-free diet by injecting bacteria into the hemocoel of fourth instars. Larvae fed CA-supplemented diet show significantly higher survival of infection with Enterococcus faecalis (Andrewes & Horder) Schleifer & Kilpper-Bälz, but not of infection with the more virulent Pseudomonas aeruginosa (Schroeter) Migula. Larvae fed on CA-supplemented diet possess a constitutively higher number of circulating hemocytes than larvae fed on the standard diet, but we found no other evidence of increased immune system activity, nor were larvae fed on CA-supplemented diet better able to suppress bacterial proliferation early in the infection. Thus, our data suggest an additional defensive function of CA to the direct toxic inhibition of pathogen proliferation in the gut.
Average (± SE) proportion of male medflies observed copulating with females at each hour at ages 2–5 days regardless of leg condition. Means with different letters within an hourly specific calling frequency are statistically different among age classes (Tukey's test: P<0.05).
of treatment type on average (AE SE) and maximum (Max) life span (days) of male medflies. Estimate (AE SE) and hazard ratio were calculated from the Cox proportional hazards model for the mated and impairment treatments. Intact unmated males formed the baseline
Injuries frequently accumulate with age in nature. Despite the commonality of injury and the resulting impairment, there are limited experimental data for the effects of impairment on life history trade-offs between reproduction and survival in insects. We tested the effects of artificial injury and the resulting impairment on the reproductive costs and behavior of male medflies, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae). Treatment flies were impaired by amputating tarsomere segments 2-5 from the right foreleg at either eclosion or age 22 days. The effect of impairment and age on the cost of reproduction was tested by varying the timing of female availability among the treatments. Courtship behavior and copulation rates were observed hourly from age 2-5 days to determine the effects of impairment on reproductive behavior. Female access combined with the impairment reduced the life expectancy of males more than the impairment alone, whereas the health effect of amputation was influenced by age. Conversely, the risk of death due to impairment was not influenced by the males' mating status prior to amputation. The males' copulation success was reduced due to impairment, whereas courtship behavior was not affected. Impairment does not reduce the males' impulse to mate but decreases the females' receptivity to copulation, while also increasing the cost of each successful mating. Overall, minor impairment lowers the reproductive success of males and reduces longevity.
The interactive effects of dietary nicotine (0.1%) and parasitism by Cotesia congregata (Say) (Braconidae) on post-ingestive utilization of food by the tobacco hornworm, Manduca sexta (L.) (Sphingidae) were studied in the laboratory. The rates of growth and consumption and the food utilization indices of third and fourth instar hornworms were not significantly influenced by the interactive effect of dietary nicotine and parasitism. However, parasitism reduced the growth rate of fifth instar hornworms, resulting from a reduction in their consumption rate. Efficiency of digestion of ingested food was enhanced in parasitized larvae, but not when they ingested diets containing nicotine. Ingestion of dietary nicotine reduced the efficiency of conversion of digested and ingested food of unparasitized hornworms as reflected in ECD and ECI values, but these indices were larger than in parasitized hosts.
A novel olefinic analog, Z,Z-1,12,14-heptadecatriene, was synthesized from Z,Z-11,13-hexadecadienal, a major pheromone component of the navel orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae), and evaluated as a potential disruptant of mating communication in commercial almond orchards. The effectiveness of the triene as a disruptant was compared to that of the aldehyde by evaluating the reduction in captures of feral males in female-baited traps and the reduction in mating success for females. The triene was highly effective in bringing about reductions in male captures in traps in all tests relative to controls. This effectiveness lasted as long as 5 weeks in one test and was influenced by type of dispenser, release rate and proximity of dispensers to female-baited traps. In none of the tests did the triene outperform the aldehyde in reducing male captures. The results of mating success tests showed the triene to be ineffective relative to controls (26% reduction) while the aldehyde yielded 100% reductions in matings during a 6-day period.
Upon testing the effects of new, non-mutagenic insect chemosterilants: benzylphenols and benzyl-1,3-benzodioxoles, we discovered that some of them show a strong and direct anti-juvenile hormone effect. This was done by means of the Galleria bioassay, adapted in such a way that juvenile hormone antagonism can be detected. A series of analogues was tested in order to compare their sterilant activity and their anti-juvenile hormone effect. The compounds which are very active in our anti-juvenile hormone bioassay are also the most active inhibitors of vitellogenesis. Effets anti-hormone juvénile de nouveaux chimiostérilisants: benzylphénols et benzyl-1,3-benzodioxoles Au cours de nos recherches sur les effets de nouveaux chimiostérilisants: benzylphénols et benzyl-1,3-benzodioxoles, nous avons constaté que quelques-uns de ces produits ont un effet antagoniste à l'hormone juvénile. Ceci a été démontré par le Gaileria bioassay, que nous avons adapté de telle façon qu'on puisse l'employer pour détecter des antagonistes de l'hormone juvénile. Ce test a été appliqué à une série d'analogues afin de comparer leur effet anti-hormonal et leur activité stérilisante. Les analogues, qui sont très actifs dans notre bioassay anti-hormone juvénile, sont aussi les meilleurs inhibiteurs de la vitellogénèse.
(3Z,6Z,9Z)-1,3,6,9-nonadecatetraene, the synthetic sex pheromone of the female of O. brumata is highly active in attracting males of this species in the field (Germany and Switzerland). No analogous compounds possessing attractivity to O. brumata males have been found up to now, nor did they show any inhibitory effects to the same species.Therefore (3Z,6Z,9Z)-1,3,6,9-nonadecatetraene (I) can be recommended as a good attractant in the prognosis or monitoring of this lepidopteran pest.
Genetic trade-offs in host plant use are thought to promote the evolution of host specificity. Experiments on a range of herbivorous insects, however, have found negative genetic correlation in host plant use in only a limited number of species. To account for the general lack of negative genetic correlation, recent hypotheses advocate that different stages in evolution of host use must be distinguished: initial performance on a novel host in comparison with the established host, and performance on both hosts after the insect population has interacted with both hosts for a long time. The hypotheses suggest that genetic correlation may not necessarily be negative at the initial stage. The present study examines growth performance on both the established and a novel host in a herbivorous ladybird beetle, Epilachna vigintioctomaculata Motschulsky (Coccinellidae, Epilachninae). The results show that traits of growth performance across hosts were positively or neutrally correlated, but there was no evidence of a negative genetic correlation. In addition, significant genetic variance of growth performance on each host was detected, suggesting that E. vigintioctomaculata can potentially respond to selection for increased performance on both plant species. These results and similar results from experiments on other herbivores suggest that host expansion may not be constrained genetically, at least at the initial stage of host range evolution.
The radioisotope 125Iodide, a gamma emittor, was used in two different forms, as 125I mixed with egg yolk and as 125I covalently attached to egg albumin and mixed with egg yolk, to study food flow in the imported fire ant, Solenopsis invicta Buren. The biological half life of 125I-albumin in egg yolk powder was determined to be 96 hr in isolated workers, 108 hr in individuals held with small groups of unlabelled workers, and 1,008 hr in workers held in colonies exposed to labelled food for 48 hr. In contrast, the biological half life of free 125I mixed with egg yolk powder was 22 hr, 20 hr, and 40 hr, respectively. The internal distribution of radioactivity was checked after 24,48, and 380 hr. There was a significant difference in distribution of 125I in ants fed either free 125I or 125I-albumin. Most of the free 125I was rapidly excreted. A high percentage of 125I-albumin was assimilated, apparently through protein digestion pathways with eventual storage in or below the cuticle. There was no evidence of gland involvement in food flow to either larvae or queens with the radio-iodinated protein.
Citrus leaves, banana squash and lemon fruit, labelled by photosynthesis, have been used as a source of 14C for red scale, Aonidiella aurantii (Mask.). The distribution of the isotope amongst the constituents of these plants has been studied using chemical methods of separation and chromatography. In citrus leaves, whether they were labelled as discs in the laboratory or in situ in the field, activity occurred as sucrose initially, but within 5 days a comparable amount was present in the amino acid, proline, and also in the insoluble carbohydrates, the proportions remaining fairly stable for long periods. Although the total activity of the leaf discs did not decrease with time, the activity of successive groups of newly hatched red scale larvae which fed on these discs for 10 days, fell significantly. It is suggested that due to the interaction of the insects' saliva with plant tissue, areas where red scale fed became depleted in activity. Sap obtained from the labelled discs contained activity in the form of sucrose and proline, but the body fluid from the mature female red scale contained activity in sucrose only. In banana squash and in lemons most of the activity occurred in the form of sugars, principally sucrose, with glucose taking up a greater proportion in the lemons; there was no appreciable activity in amino acids and a much smaller fraction in the insoluble carbohydrates.
The possiblity of using 14C to mark red-scale for ecological studies has been investigated. Citrus leaves were labelled with 14C to have an activity in the range 3-300 μ Ci gm-1. All insects feeding on these leaves became radioactive. Mature females had an activity of 5000-160,000 c.p.m., mature males an activity of 1000-16,000 c.p.m. and the progeny of the females labelled to the level of 10,000 c.p.m. had an activity of 10-30 c.p.m. Higher levels of activity affected the development and fecundity of the insects. High mortality was observed in first-instar larvae which had an activity ≥10,000 c.p.m. and in second-instar larvae which had an activity ≥20,000 c.p.m. Fertilized females which had an activity of 30,000 c.p.m. did not reproduce. The marking method has been extended to the mass-rearing of labelled insects on green melons which have incorporated 14C during photosynthesis.
European corn borer larvae, Ostrinia nubilalis (Hbner) (Lepidoptera: Crambidae) that have completed development on Event 176 Bt corn hybrids have survived exposure to sublethal doses of the Cry1Ab Bt toxin or are exploiting plant tissues that do not express the toxin. To evaluate the impact of such exposure, diapausing larvae were collected from Event 176 and conventional hybrids and compared for rates of pupation, parasitism, fitness (pupal weight, longevity, and fecundity) and susceptibility to the Cry1Ab toxin. Larvae completing development on Event 176 corn exhibited approximately 10% higher survival rates and correspondingly lower parasitism rates than larvae completing development on conventional hybrids. No significant differences were detected in pupal weight, fecundity, longevity or susceptibility to the Cry1Ab Bt toxin. These results indicate that survival on Event 176 corn are not adversely affect fitness and does not cause increased tolerance to the Cry1Ab toxin in subsequent generations.
It was found that the reproductive separation between the two-spotted spider mite (Tetranychus urticae Koch) and the carmine spider mite (Tetranychus cinnabarinus (Boisduval)) is far from complete. Hybrid strains were established which possessed the morphological characteristics of T. cinnabarinus, but which were homozygous for a marker gene originating from T. urtica. In addition, short-day treatment leads to diapause not only in the species from cold climates (T.urticae), but also in a population of T. cinnabarinus. It is questioned whether T. cinnabarinus deserves ranking at species level. Ce travail montre que l'isolement reproductif entre Tetranychus urticae Koch et Tetranychus cinnabarinus (Boisduval), est loin d'être complet. L'auteur a obtenu des souches hybrides présentant les caractéristiques morphologiques de T. cinnabarinus, mais homozygotes pour un gêne marqueur provenant de T. urticae. De plus, une diminution de la photopériode entraîne l'entrée en diapause des espèces provenant de régions à climat froid (T. urticae), mais aussi d'une population de T. cinnabarinus. Il est finalemant proposé de considérer Tetranychus cinnabarinus (Boisduval) Boudreaux, 1956, comme un synonyme de Tetranychus urticae Koch, 1836.
The literature on Aedes togoi is reviewed. This oriental mosquito occasionally acts as a vector for filarial or virus diseases and is sometimes a nuisance from its bites. Eggs from Taiwan (Formosa) were brought to London in 1958. A laboratory colony was reared from these eggs and maintained by methods similar to those commonly used for Aedes aegypti. Various aspects of the bionomics were studied, including the lengths of stages, mortality during development and the effects of copulation, feeding and salt content of water on oviposition. The levels of susceptibility to DDT, BHC and dieldrin were measured by the World Health Organisation (W.H.O.) method and compared with those of colonies of A. aegypti originating in Taiwan and the Pescadores.
Sticky aphid-traps were operated over potato crops at Rothamsted during 18 years, and elsewhere for shorter periods, to get information about the activity of Myzus persicae in relation to the spread of virus diseases. Numbers of total aphids, M. persicae, Aphis fabae and Brevicoryne brassicae caught per week are given. Annual rhythms in aphid numbers were unpredictable, although there was a tendency for A. fabae to be few during the year after one in which they had been numerous. M. persicae were few in summer when they and their predators or parasites had been numerous in spring, and were often numerous in summer when they had been few in spring. A. fabae were more numerous during most years than M. persicae, and B. brassicae usually scarce. Severe winters affected M. persicae more than the other two species.
The cyclic amino alditol 2,5-dihydroxymethyl 3,4-dihydroxypyrrolidine (DM DP) has recently been shown to be an inhibitor of various glucosidases. We have investigated its role as a plant protective chemical against a range of phytophagous insects by examining its effects on development, feeding behaviour and functioning of taste receptors. We have shown that it can inhibit feeding and can be toxic. The mechanisms by which these effects are achieved are discussed in the context of the molecular structure of the compound. L'action phagodissuadante sur les insectes d'un composé secondaire végétal: 2,5 dihydroxymethyl 3,4 dihydroxypyrrolidine (DMDP) Récemment a été mis en évidence le puissant pouvoir inhibiteur de différents glucosidases. Présenté par l'amino-alditol cyclique, 2,5 dihydroxymethyl 3,4 dihydroxypyrrolidine (DMDP), isolé de graines de la légumineuse Lonchocarpus sericeus. Nous avons examiné le rǒle de ce composé secondaire dans la stratégie défensive de la plante contre une gamme d'insectes phytophages, à travers son action sur le développement, le comportement alimentaire et le fonctionnement des récepteurs gustatifs. Nous avons montré que DMDP peut inhiber, suivant la dose, la prise de nourriture et, qu'après ingestion (par Spodoptera spp), il peut agir comme une toxine. Par suite de sa structure moléculaire, DMDP peut ětre considéré, non seulement comme l'analogue d'un sucre, mais aussi comme un alcaloïde. Le bilan des résultats de nos expériences suggère que l'efficacité de DMDP comme phagodissuadant, si elle ne provient pas de sa toxicité, découle principalement de ses propriétés d'alcaloïde.
The secondary plant compound 2,5-Dihydroxymethyl-3,4-dihydroxypyrrolidine (DMDP), an analogue of β-D-fructofuranose, is lethal to the larvae of the bruchid beetle Callosobruchus maculatus F. when incorporated into artificial diets at levels greater than 0.03%. In the range 0.003% to 0.03% the compound reduces larval survival in a dose-dependent manner. The α-D-glucosidase digestive enzyme demonstrated in homogenates of the alimentary tract of the larvae is strongly inhibited by the compound in a competitive manner. Toxicité de la substance secondaire 2,5-Dihydroxyméthyl-3,4-dihydroxypyrrolidine pour les larves de Callosobruchus maculatus et effets sur les carbohydrases digestive des larves La substance secondaire 2,5-dihydroxyméthyl-3,4-dihydroxypyrrolidine (DMDP), analogue du β-fructofuranose, est létale pour les larves de C. maculatus lorsqu'elle est incorporée dans des régimes alimentaires à des taux supérieurs à 0,03%. Entre 0.003% et 0.03%, la substance réduit la survie larvaire proportionnellement à la dose. L'enzyme digestive α-D-glucosidase observée dans les homogénats du tube digestif de la larve est fortement inhibée par la substance d'une façon compétitive.
The variety AF-28 of Sorghum bicolor Pers and the hybrid R-1090 were compared in relation to the sorghum midge, Contarinia sorghicola (Coquillet), (Diptera: Cecidomyidae) in two counties of the State of São Paulo. They were compared in seven successive monthly trials beginning in September 1972. Averages of 252 and 137 adult flies emerged per head of the hybrid R-1090 in Campinas and Jaboticabal respectively, while 2.9 and 0.8 emerged from AF-28. The damage was graded with a visual scale from 0 to 4. Average damage grades of 3.5 and 3.3 were attributed to the hybrid R-1090 in Campinas and Jaboticabal respectively, while the variety AF-28 had averages of 0.5 and 0.3, respectively. RÉSISTANCE DE LA VARIÉTÉ AF-28 À CONTARINIA SORGHICOLA (DIPTERA: CECIDOMYIDAE) La variété AF-28 et l'hybride R-1090 de Sorghum bicolor Pers. ont été comparés à différentes époques de l'année et en deux localités différentes de l'Etat de São Paulo, Brésil. On n'a pas constaté d'interaction variété x époque ou variété x lieu. AF-28 a prouvé sa résistance à toutes les époques, aussi bien dans un lieu que dans l'autre; l'hybride par contre s'est montré grandement susceptible. Des moyennes de 252,2 et 136,7 mouches par panicule ont été observées pour l'hybride R-1090 à Campinas et à Jaboticabal contre 2,9 et 0,8 seulement par panicule de AF-28. Le préjudice a été estimé visuellement selon une échelle de 0 à 4. Des préjudices d'une valeur moyenne de 3,5 et 3,3 ont été attribués à l'hybride R-1090 à Campinas et à Jaboticabal respectivement, alors que simultanément la variété AF-28 ne subissait que des préjudices évalués à 0,5 et 0,3 respectivement. Quatre espèces de microhyménoptères parasites de Contarinia sorghicola ont été récoltées au cours de ce travail: Eupelmus popa et trois espèces différentes du genre Tetrastichus.
Surviving F2 wingless individuals with an indication of the degree to which they expressed the wingless trait
Numbers of wingless and normally winged F4 indi- viduals produced by each breeding group
A viable wingless 2spot ladybirdAdalia bipunctata (L.) was found in the wild. Breeding through four generations revealed that the wingless trait was controlled by a recessive allele which displays variable levels of expression. The wingless ladybird is discussed in relation to its potential as a biocontrol agent. One ladybird also occurred in this stock which is suggestive of a supergene controlling the colour polymorphism in this species.
(Z)-3-nonenol, (Z,Z)-3,6-nonadienol and (S,S)-(-)epianastrephin proved active as male-produced pheromones which elicited behavioral responses from virgin female Mexican fruit flies (Anastrepha ludens) (Diptera: Tephritidae) in laboratory bioassays. All three chemicals elicited attraction and/or locomotor arrest when tested individually. When tested together, (Z)-3-nonenol inhibited the behavioral effect of (Z,Z)-3,6-nonadienol but either of the alcohols synergized the effect of (S,S)-(-)-epianastrephin. Quantities of the pheromones per male abdomen were: (Z)-3-nonenol −100 ng; (Z,Z)-3,6-nonadienol −40 ng; and total epianastrephin (R,R and S,S enantiomers) −700 ng. Relative to the quantities in abdominal extract, males released these chemicals during sexual display in a blend containing a higher proportion of the alcohols. (Z)-3-nonènol, (Z,Z)-3,6-nonadiènol et (S,S)-(-)-é-pianastréphine: Phéromones produites par le mâle de la mouche mexicaine du fruit Le (Z)-3-nonènol, le (Z,Z)-3,6-nonadiènol et le (S,S)-(-)-épianastréphine produits par les mâles de la mouche mexicaine du fruit (Anastrepha ludens) (Diptera: Tephritidae) ont attirés les femelles lors de tests conduits en laboratoire. Le pouvoir attractif du (Z)-3-nonènol est faible comparé à celui des deux autres phéromones. Evalués ensemble, le (Z)-3-nonènol inhibe l'attractivité du (Z,Z)-3,6-nona-diènol mais chacun des deux alcools synergise l'effet attractif de la (S,S)-(-)-épianastréphine. Les quantités recouvrées par mâle dans un extrait abdominal étaient respectivement de 100,40 et 700 ng pour le (Z)-3-nonènol, le (Z,Z)-3,6-nonadiènol, et l'épianastréphine totale (R,R et S,S) énantiomères. Comparées à ces valeurs, le mélange émis par les mâles lors de leur cour sexuelle est plus riche in alcools. Le rapport (Z)-3-nonènol (Z,Z)-3,6-nona-diènol est cependant identique dans l'extrait abdominal et dans le mélange émis par les mâles.
Techniques for 32P labelling of larvae and adults of the screw-worm fly, Chrysomya bezziana, are described. Egg masses of labelled flies were readily identified. At the doses used for field releases, oviposition activity, fecundity, fertility and longevity of female flies were not adversely affected. Radioactive egg masses were recovered from sentinel animals following field release of labelled flies. ESSAIS DE MARQUAGE AVEC 32p DU DIPTÈRE CHRYSOMYA BEZZIANA “THE OLD-WORLD SCREW-WORM FLY” Cet article décrit les techniques utilisées pour marquer avec le 32p les larves et adultes de Chrysomya bezziana. Les pontes des mouches marquées ont été aisément identifiées. Aux doses utilisées pour le relâchement des insectes dans la nature, ni l'activité de ponte, ni la fécondité, fertilité et longévité des femelles n'ont été défavorablement modifiées. Les pontes radioactives ont été recueillies sur des animaux-pièges mis en place après le lâcher des mouches marquées.
Most adult male codling moths, Cydia pomonella (L.), were sterile when they were transferred from 26° to 33°C at various larval stages. Exposures to 33° increased mortality (on average by 26.5%) and resulted in 48.5% and 30.7% fewer matings by treated males and females, respectively. APFEL WICKLER: EFFEKTE EINER ZUCHTTEMPERATUR VON 33° FÜR RAUPEN UND PUPPEN ***AUF ÜBERLEBEN UND VERMEHRUNG Wenn Raupen des Apfelwicklers, Cydia pomonella (L), in verschiedenen Zeitpunkten von 26° zu 33° gebracht wurden, waren die meisten Falter steril. Zudem erhöhte die Zuchttemperatur 33° die Mortalität (Erhöhung um durchschnittlich 26,5% gegenüber unbehandelt) und reduzierte die Kopulationen der behandelten Männchen um 48.5% und der behandelten Weibchen um 30.7%.
The radioactivity of the honeydew droplets excreted by young apterous adults of the green peach aphid, Myzus persicae, fed on an artificial diet containing 3H-inulin was a reliable measure of the volume of food ingested by the insects, since almost none of the ingested inulin was absorbed and retained by the insects. Quantitative Bestimmung der Nahrungsaufnahme von Aphiden auf künstlicher Diät mit3H-Inulin Junge aptere Adulte von Myzus persicae wurden auf künstlicher Diät mit oder ohne Zugabe von radioaktiv markiertem Inulin (3H, 100 μCi pro ml; 84.5 cpm pro nl) gehalten. Die Radioaktivität der Blattläuse und ihrer ausgeschiedenen Honigtautropfen wurde in Zeitintervallen nach der Fütterung bestimmt. Die Ergebnisse zeigen, dass Inulin nur in geringer Menge von den Blattläusen absorbiert wird, und, dass die Radioaktivität der ausge schiedenen Honigtautropfen nach Zugabe von 3H-Inulin zur künstlichen Diät ein verlässliches Mass für das Volumen der von ihnen aufgenommenen Nahrung ist.
Biological activity assays with RH 5849 and RH 5992 indicated that both compounds affected growth and development of last-instar larvae ofSpodoptera exigua (Hübner) (Lepidoptera: Noctuidae) in a dose-dependent manner. Within the first 24 h after treatment by continuously offering leaves dipped in a water solution of ≥50 mg/l RH 5849 and ≥0.5 mg/l RH 5992, symptoms of a prematurely induced larval moult and head capsule apolysis were visible. Intoxicated larvae died shortly afterwards, showing signs of unsuccessful ecdysis. LC50-values of RH 5849 and RH 5992 for fifth-instarS. exigua larvae were 110 and 2.5 mg/l, respectively. Pyriproxyfen alone affected the larval stage and disturbed normal metamorphosis. One supernumerary larval instar occurred occasionally. LC50-value for pyriproxyfen was 1.7 mg/l. Larvae simultaneously treated with RH 5849 or RH 5992 and pyriproxyfen, continued to grow until they attained a size and weight about 2–3 times that of the controls. This growth was accompanied by at least one and sometimes two supernumerary moults. Concerning thein vivo imaginal wing disc growth and development, only in larvae treated with 10 and 50 mg/l RH 5849 or 0.5 mg/l RH 5992, tracheole migration was observed earlier than in the controls. When applying 300 mg/l RH 5849 or 3–7 mg/l RH 5992, the discs remained small and no signs of tracheole migration were observed. In larvae simultaneously treated with RH 5849 or RH 5992 and pyriproxyfen, tracheole migration was not prematurely induced and a pupal cuticle was produced in the discs of larvae, undergoing a supernumerary moult. No clear signs of evagination were observed.
Wing-pad lengths of fifth-instarN. lugens andS. furcifera were investigated as indicators of adult wing-morph. Below critical values all resultant adults are brachypterous. Above these values some laboratory-reared fifth instars became either brachypterous or macropterous. The use of this technique in studying the dynamics of field populations is discussed. Une distribution bimodale des fréquences de la longueur des ébauches alaires a été observée chez les larves mâles et femelles du cinquième stade deN. lugens et chez les larves femelles du même stade deS. furcifera. La fiabilité de l’utilisation de ces mesures comme indicateur du dimorphisme alaire des adultes a été examinée. Les études au laboratoire ont montré que les larves de cinquième stade aux ébauches alaires courtes donnent toujours des adultes brachyptères, tandis que celles aux ébouches alaires alongées peuvent donner des adultes alongées macroptères ou brachyptères. Ceci suggère une détermination en deux étapes du développement du type alaire dans cette catégorie de larves du cinquième stade. L’utilisation de cette technique pour étudier la dynamique des populations deN. lugens etS. furcifera dans la nature est discutée.
In 124 days of field tests, 88.7% of male, 87.3% of female, and 90.2% of 5th-instar Nezara viridula were caught on cages containing male N. viridula rather than on female or control cages. Likewise, 92% of the female and 86% of the male parasite, Trichopoda pennipes (F.), were caught on cages containing male N. viridula. Attraction of N. viridula occurs throughout the daylight hours, but is strongest in a 5-min period immediately prior to complete darkness. The data suggest the presence of a male-emitted aggregation pheromone in N. viridula, acting concomitantly as a kairomone for T. pennipes females. DURCH MÄNNCHEN VERURSACHTE ANSAMMLUNG VON MÄNNCHEN, WEIBCHEN UND 5. STADIUMLARVEN VON NEZARA VIRIDULA UND GLEICHZEITIGE ANLOCKUNG DER TACHINIDE, TRICHOPODA PENNIPES Es wurden im Sommer und Herbst Käfige auf Feldern verschiedener Kulturpflanzen aufgestellt. In jeden Käfig wurden Nezara viridula (Hemiptera: Pentatomidae)-Imagines eingesetzt, die geschlechtsweise so sortiert waren, dass jeder Käfig ausschliesslich Weibchen, ausschliesslich Männchen, oder gleiche Mengen beider Geschlechter enthielt. Freilebende N. viridula wurden von den eingesperrten Insekten angelockt. Jeweils über 87% der Männchen, Weibchen und der Altlarven, die angezogen wurden, kamen an die Käfige, die Männchen enthielten. Die Schmarotzerfliege Trichopoda pennipes (Diptera: Tachinidae) wurde auch angelockt — hier fanden sich 92% der weiblichen und 86% der männlichen Fliegen auf den Käfigen, die männliche Wanzen enthielten. Die Anlockung der Hemipteren dauerte den ganzen Tag an, mit einer vorübergehenden, aber sehr starken Zunahme direkt vor dem Einbruch der Dunkelheit. Wir nehmen an, dass N, viridula-Männchen ein Pheromon abgeben, das nicht nur Weibchen, sondern auch andere Männchen, Larven und auch Schmarotzerfliegen anzieht. Das Verhalten der Insekten blieb immer gleich in den beiden Jahreszeiten, und auch die verschiedenen Pflanzenarten hatten keinen Einfluss darauf.
An artificial bean seed system was used to evaluate the effects of a cysteine proteinase inhibitor (E-64) and a serine proteinase inhibitor (Bowman-Birk inhibitor) on the developmental time and mortality of the common bean weevil, Acanthoscelides obtectus (Say). These inhibitors were incorporated into artificial bean seeds on which the insect fed. To better understand the mode of action of these inhibitors, free amino acids were also added to the seeds, alone and in combination with the inhibitors. E-64 was found to be highly effective in delaying development and increasing mortality of the insect. Both effects were directly related to the concentration of E-64. Bowman-Birk inhibitor had little effect on these parameters. Assays of gut proteolytic activity of insects reared on artificial seeds with various levels of E-64 demonstrated a direct relationship between E-64 concentration in the diet and reduction of gut proteolytic activity. Free amino acid supplementation to the diet did not prevent inhibition of gut proteolytic activity by E-64, but did reverse its effects on developmental time and mortality, strengthening the hypothesis that E-64 operates by inhibition of essential digestive proteinase activity.
Effects of the radioisotope 65Zn used to label Colpoclypeus florus Wlk. were studied. Labelled parents did not show any decrease in parasitizing ability. Radioactive labelling shortened the adult life span to a certain degree depending on rearing conditions. It also increased embryonic and larval mortality of the progeny to some extent. EFFET DU MARQUAGE AVEC LE RADIOISOTOPE65Zn SUR LA BIOLOGIE D'UN EULOPHIDE, COLPOCLYPEUS FLORUS, PARASITE DE TORTRICIDAE L'effet du radioisotope 65Zn, utilisé comme traceur, a été mis à l'épreuve sur Colpoclypeus florus, ectoparasite grégaire s'attaquant fréquemment aux Tortricidae dans les vergers de pommiers aux Pays-Bas. Les C. florus adultes, marqués avec 65Zn en leurs donnant accès pendant 2 jours à du miel contenant cet isotope, présentent par comparaison avec des parasites alimentés de miel pur, une réduction d'environ 50% de la longévité dans des conditions permettant, ordinairement, une survie prolongée. L'aptitude à coloniser les larves-hôtes et le nombre d'oeufs déposés par larve-hôte ne sont pas modifiés, mais le taux d'éclosion et la survie des larves du parasite sont diminués de 5% à 10% par le traceur. Ainsi, avant toute étude de la dispersion du parasite après libération en verger, d'autres traceurs radioactifs doivent être testés.
The effects of tree species, shoot age, and sex of larvae on food consumption and utilization were investigated in a factorial experiment. Diets prepared from lyophilized and powdered current-year shoots, from two age classes (sample dates) of Picea glauca (Moench) Voss, Picea rubra Sarg., and Picea mariana (Mill.) B.S.P., were evaluated for eight performance criteria. All factors had significant effects on all criteria except for tree species on assimilation efficiency, shoot age on development time, and sex on net growth efficiency. Eight of the possible 24 two-factor interactions and one of the possible eight three-factor interactions were significant. Food utilization efficiencies and relative growth rate were in the low and moderate characterization limits for immature arthropods; relative consumption rates were high. The higher performance values on Picea glauca were related to this species greater vulnerability to spruce budworm. Performance criteria of similar larvae on an artificial diet were compared with those on the foliage-diets.
A descriptive study of the feeding behavior and structures of Trichogramma brassicae Bezdenko (Hymenoptera: Trichogrammatidae) was conducted. Based on direct observational and biochemical evidence, larvae feed predominantly on particulate materials, starting ca. 25h post-oviposition. Feeding lasted for ca. 9h, at 251C. During this feeding period the shape of the larvae changed from vermiform to pyriform and then to sacciform, resulting in a ca. 40-fold increase in body size. Larvae used elaborate feeding behaviors as they pulled solid food particles to their oral opening, broke small particles from larger ones, and took the particles into the stomodaeum, which is a powerful pump. In the stomodaeum, peristaltic movement further macerated the particles, which eventually passed through the cardiac valve into the midgut. As indicated by changes in fluorescently labeled casein, digestive enzymes aid in the extra-oral chemical digestion of food. The contents of the gut, during and shortly after feeding, were almost entirely closely packed solid particles. The behavioral activity of feeding larvae centered almost exclusively on processing and ingesting solid food particles. The rapid larval growth is much more plausibly explained by their feeding on the highly concentrated nutrients found in solid foods, rather than the extensive concentration required if dilute liquids were the principal source of nutrients. The implications of these findings for the development of practical artificial diets are discussed.
Courting males of the parasitic wasp Nasonia vitripennis appear to release a pheromone with the extrusion of mouth parts during so-called head-nodding behaviour. This pheromone provokes sexual receptivity in conspecific virgin ♀ ♀. Abdomectomized ♂ ♂ court readily but have lost the ability to induce receptivity. Head nodding, mouth-part extrusion, and presumably also pheromone discharge, are absent from their courtship behaviour. However, plugging the injury results in reappearance of these motor patterns, and restores courtship success to the level of intact controls. We present some evidence for a hydraulic system involved in pheromone discharge (with head nodding and mouth-part extrusion). At the same time we present evidence, based on comparative data, that this system is unlikely to be a simple “on-and-off” type behaviour. Balzverhalten von Nasonia vitripennis: Kopfnicken, Ausstrecken der Mundteile und Pheromonabgabe von hinterleibamputierten Männchen Männchen der Schlupfwespe Nasonia vitripennis produzieren ein Pheromon, das virginelle Weibchen paarungsbereit macht. Während der Pheromonabgabe strecken die Männchen unter Kopfnicken die Mundteile aus. Hinterleibamputierte Männchen sind immer noch balzfreudig, zeigen aber weder Kopfnicken noch Ausstrecken der Mundteile und die von ihnen bebalzten Weibchen wurden nie paarungsbereit. Wird die Schnittwunde mit Leim bedeckt, so balzt das hinterleiblose Männchen wie zuvor, aber mit ganz normalem Erfolg. Wir vermuten die Wirkung eines hydraulischen Systems bei der Pheromonabgabe. Wir bringen aber weitere, vergleichende Daten vor, die zeigen, dass ein solches System, wenn überhaupt wirksam, nicht einfacher Natur (“An-aus-System”) sein kann.
The isolated honey bee abdomen has been used for the qualitative detection of possible autoneurotoxins released into the haemolymph of cockroaches, kept in a colony, in response to stress induced by handling. When haemolymph containing toxic substances is introduced into the honey bee abdomen there is an increase in the frequency and amplitude of the spontaneous contractions. Two hours after stress the haemolymph no longer showed any evidence of stimulating substances when tested on the abdomen. Cockroaches maintained in isolation offered little resistance to handling and autotoxins did not appear in the haemolymph. These responses in the cockroaches are similar to those observed previously in the bee. EMPLOI DE L'ABDOMEN ISOLÉ D'ABEILLE POUR MESURER LES EFFETS D'UN «STRESS» CHEZ LA BLATTE AMÉRICAINE Les neurotoxines qui peuvent être libérées dans l'hémolymphe d'une blatte à la suite du stress provoqué par sa capture et sa préhension entre les doigts, sont mises en évidence en utilisant comme réacteur biologique l'abdomen isolé d'abeille. L'injection ou la transfusion (cf. texte) dans l'abdomen isolé, du sang d'une blatte soumise à un tel stress, provoque un accroissement de la fréquence et de l'amplitude des contractions musculaires spontanées de l'abdomen. Les substances excitatrices présentes dans l'hémolymphe de la blatte disparaissent deux heures après le stress qui les a engendrées. Ces substances dites «autotoxines» n'apparaissent pas dans le sang de blattes isolées, qui ne montrent que peu de résistance à être manipulées à la main; elles sont au contraire d'autant plus abondantes ou actives que les blattes sont groupées en plus grand nombre, conditions dans lesquelles elles présentent un stress maximum lors de leur capture à la main. Ces réponses chez la blatte sont comparables à celles qui ont éTÉ anTÉrieurement observées chez l'abeille.
Perception of the oviposition deterring pheromone by contact chemoreceptors in female Pieris brassicae was studied employing a tip recording technique. Electrophysiological responses of tarsal taste hairs to egg-wash solutions show a marked increase in frequency of spikes originating from only one sensory cell. This suggests that in foretarsal taste hairs females, apart from the glucosinolate cells also possess sense cells specifically sensitive to the oviposition deterring pheromone. Morphological studies by means of the scanning electron microscope revealed that the ovipositor of P. brassicae is provided with two groups of contact chemoreceptors. Electrophysiological recordings from these sensilla indicate the presence of at least three sensory cells, one of them being a mechanoreceptor. Stimulation with eggwash evokes a slight increase in spike frequency which cannot be ascribed to one particular sense cell. This indicates that abdominal taste hairs in some way may participate in the perception of the oviposition deterring pheromone. Responses to glucosinolates do not differ significantly from control stimulations. Perception de la phéromone dissuadante de la ponte par les récepteurs chimiques de contact des tarses et de l'abdomen chez Pieris brassicae Une technique d'enregistrement apical a été utilisée pour examiner la perception d'une phéromone dissuadant la ponte par les poils récepteurs chimiques de contact des femelles de Pieris brassicae. Les réponses électrophysiologiques des poils gustatifs des tarses en présence de solutions de rinçage d'oeufs présentent une fréquence marquée des potentiels d'action provenant principalement d'une cellule sensorielle. Ceci suggère que les poils gustatifs des tarses des pattes antérieures des femelles possèdent, en plus de cellules répondant aux glucosinolates, des cellules sensorielles sensibles spécialement à la phéromone dissuadant la ponte. Des études morphologiques au microscope à balayage révèlent que l'oviposition de P. brassicae est pourvu de deux groupes de chimiorécepteurs de contact. Des enregistrements électrophysiologiques de ces sensilles révèlent la présence d'au moins trois cellules sensorielles, l'une d'entre elles étant un mécanorécepteur. La stimulation avec la solution de rinçage des oeufs évoque un léger accroissement de la fréquence des potentiels d'action qui ne peut être attribué à une cellule sensorielle particulière. Ceci indique que les poils gustatifs abdominaux peuvent participer d'une certaine façon à la perception de la phéromone dissuadant la ponte. Les réponses aux glucosinolates ne diffèrent pas significativement des stimulations témoin.
Transgenic potatoes have been transformed with a gene coding the snowdrop lectin Galanthus nivalis agglutinin (GNA) and they have been shown to be partially resistant to aphids. GNA binds to insect gut cells, including those of aphids, consequently inducing disruption of nutrient assimilation. Aphid parasitoids are important natural biocontrol agents of aphids and some species such as Aphelinus abdominalis are commercially available. Aphid parasitoids are endoparasitoids during their larval stages and free-living insects as adults. They could be directly or indirectly affected by GNA during both these stages. In this work, we present data on the potential direct and indirect effects of GNA on adult A.abdominalis. Aphelinus abdominalis is a synovigenic species (eggs are matured throughout the adult life) which needs a diet relatively rich in proteins and amino-acids to produce anhydropic eggs (large, yolk-rich eggs that do not expand in the host during embryonic stages). Adult A.abdominalis females feed on aphid haemolymph and they may be directly exposed to the entomotoxin or indirectly affected by a change in aphid haemolymph quality due to intoxication by GNA. We conducted a first tier experiment to investigate this potential risk. A.abdominalis females were offered either aphids reared on control diet or aphids reared on GNA 0.1% diet as hosts (i.e., as food and oviposition sites). No trace of GNA was found in females fed with GNA-aphids but no GNA could be detected in the haemolymph of aphids fed a 0.1% GNA diet. Longevity and fecundity were not affected suggesting that the quality of the haemolymph necessary for A.abdominalis egg maturation and production was not significantly altered.
Using an electronic device and a lignin-specific dye, the feeding behaviour of the green leafhopper, Nephotettix virescens (Distant), (Homoptera: Cicadellidac) was monitored on rice plants kept in an arena permeated with the odour of neem (Azadirachta indica A. Juss) seed oil. The garlicky odour of neem oil disrupted the normal feeding behaviour of the leafhopper. Phloem feeding by N. virescens on rice plants kept in an arena permeated with odour of 6, 12, or 25% neem oil was significantly reduced compared with that on control plants kept in an arena with paraffin oil or 1.66% aqueous ‘Teepol’ solution. Reduced intake from phloem was associated with a significant increase in the insect's probing frequency and an increase in durations of salivation and xylem ingestion. A Itérations du comportement alimentaire sur riz de Nephotettix virescens, dues à l'odeur d'essence de neem (Azadirachta indica) De nombreux essais en plein champ à l'I.R.R.I. ont révélé une réduction du T.V. (tungro virus) transmis par (Nephotettix virescens) sur des parcelles de riz sensible nontraitées, entourées de parcelles pulvérisées périodiquement avec de l'essence de graines de neem (Azadirachta indica). L'essence de neem a une forte odeur d'ail, perceptible à distance. Nous avons examiné l'effet de l'odeur d'essence de neem sur le comportement alimentaire de N. verescens, grâce à un dispositif électronique et un colorant spécifique de la lignine. Sur du riz maintenu dans une enceinte imprégnée d'odeur d'essence de neem, nous avons constaté une diminution de la consommation de phloème, une augmentation significative de la fréquence des piqûres et une augmentation de temps de salivation et d'absorption de xylème. Ces altérations du comportement alimentaire provoquées par l'odeur d'essence de neem peuvent expliquer la diminution de la fréquence du T.V. spécifique du phloème dans des champs de riz non-traités, entourés de champs pulvérisés avec de l'essence de neem.
Die groe Regurgitationstendenz im Ftterungsverhalten von Ameisen wurde ausgentzt, um mit Hilfe der Tracermethode (J131 in Honigwasser) die Nestareale holzzerstrender Roameisen (C. herculeanus) in lebenden Bumen zu ermitteln. Hierzu wurden vorher im Laboratorium Absorptionsmessungen an verschiedenen Hlzern und mit verschiedenen Detektoren vorgenommen. Hierbei ergab sich fr den Szintillationszhler der gnstigste Wirkungsgrad. Die Freilanduntersuchungen zeigten, da die Nestareale einer einzigen Kolonie eine Reihe von Stmmen umfassen knnen und weit grer sind, als die uerlich erkennbaren Schadbilder vermuten lassen.Regurgitation is important in the feeding behaviour of ants. Iodine131 in honey-water-solution was fed to colonies of Camponotus herculeanus. A scintillation counter was used to determine the nest area, i.e. that which was radioactive following regurgitation. This apparatus gave the most consistent results with different woods. The nest area of a single colony was found to include several trunks, and covered a much larger area than the external damage revealed.
Geprft wurde die Bildung der Diapauseform bei Phosphorsureester-anflligen, retroresistenten, heteroresistenten und hochresistenten Stmmen von Tetranychus urticae Koch. Zu den bisher festgestellten biologischen Unterschieden zwischen anflligen und resistenten Tieren wurde die Frage diskutiert, ob sie auf eine gemeinsame Ursache — das neurosekretorische System — zurckgefhrt werden knnen.The production of the diapausing form of Tetranychus urticae was studied under constant conditions, with 9 hours light, 13 C and 85% relative humidity. Four strains with different degrees of resistance to organophosphorus insecticides were used. Their resistance to Tepp is shown in Figure 1 (page 265). One strain (A) was susceptible, another (R), very resistant; the others (RR = retroresistent and HR = heteroresistent) were intermediate.67% of the females of the susceptible strain entered diapause, none of the most resistant strain did so. The RR strain gave 27% and the HR 16% of diapausing individuals.Some females showing apparently characteristic colour changes did not enter diapause. No diapause was seen in males.The relationship between changes in the neurosecetory system in these different strains and the onset of diapause is discussed.
Gas chromatographic analyses coupled with electro-antennographic detection indicated that (Z,E)-9,11-tetradecadienyl acetate (Z,E-9,11–14Ac) is a pheromone component of the cone pyralid Dioryctria abietella. Gas chromatographic − mass spectrometric analyses confirmed the presence of a tetradecadienyl acetate with mass spectrum and retention index identical to Z,E-9,11–14Ac. A receptor cell sensitive to both Z,E-9,11–14Ac and the female extract was identified on the male antenna. An additional receptor cell sensitive to (Z)-9-tetradecenyl acetate and (Z,E)-9,12-tetradecadienyl acetate was found on the male antenna but was not activated by the female extract. In the field Z,E-9,11–14Ac presented alone attracted significant numbers of male D. abietella. Addition of (Z)-9-tetra-decenyl acetate inhibited the attraction of males to traps.
Field and laboratory observations of the relationships between the performance of Elatobium abietinum (Walker), Homoptera, Aphididae, and various species of spruce were undertaken from January 1980 to April 1981. The study included sampling for aphids in established field plots of spruce during May and June respectively before and after the migration period in spring. The aphid's performance (weight and mean relative growth rate) at different seasons on pot grown plants of selected spruce species was monitored, covering, in all, 20 species of spruce. Aphid performance was greatest on the North American spruces, especially Picea sitchensis (Bong) Carr and P. mexicana Martinez; the Asian spruces were the least favoured, especially P. glehnii (Schmidt) Mast. Between these two geographical groups the Eurasian spruce species (sensu Wright, 1955) demonstrated an intermediate aphid performance. Dégàts et performances du puceron, Elatobium abietinum sur 20 espèces d'épicéas Les observations dans la nature et au laboratoire sur les performances d'E. abietinum Walker et différentes espèces d'épicéas ont été effectuées de janvier 1980 à avril 1981. Les observations dans la nature comprenaient des prélèvements de pousses d'épicéa pour dénombrer les pucerons avant (mai) et après (juin) la période de migration du printemps. Les performances des pucerons (poids et taux moyen de croissance relative) ont été examinées à différentes saisons sur des plantes en pot sur un total de 20 espèches sélectionnées d'épicéas. Les performances du puceron ont été supérieures sur les espèces d'épicéa de l'Amérique du nord Picea sitchensis et P. mexicana; les espèces asiatiques étaient les moins favorables, particulièrement P. glehnii. Entre ces deux groups géographiques, les espèces eurasiennes (sensu Wright, 1955) ont permis des performances intermédiares chez les pucerons.
The attraction of Hylobius abietis (L.) (Coleoptera: Curculionidae) to -pinene was recently shown to be inhibited by limonene. This study shows that added limonene also affects the response of H. abietis to odours from natural host material. The experiments included both pieces of Scots pine suspended in pitfall traps and planted pine seedlings that had either been manually wounded or left intact. By adding a limonene dispenser, the catch of pine weevils in pine-baited traps was reduced by about 80–90% in spring and autumn and by about 40–50% in summer. Limonene substantially reduced the rate at which manually wounded seedlings were attacked by weevils in spring and autumn. For intact seedlings, a limonene-induced reduction in attack rate was found only in autumn. In the absence of limonene, a small wound made on the stem of a seedling increased its probability of being attacked by about fivefold. This figure was estimated by comparing data from all experimental periods with a model assuming a constant ratio of attack rates for the two kinds of seedlings.
Pine weevil, Hylobius abietis (L.) (Coleoptera: Curculionidae), movement behaviour on different substrates was studied in an indoor arena using a video camera and digital image processing technique. We analysed individual variation in movement characteristics, i.e. turning angles, movement directions, and distance moved per unit time on the bare and level arena surface which consisted of mineral soil (sand) and/or humus sections in various spatial configurations. Pine weevils on humus did not turn back when they came to the border with the sand. However, most individuals moved faster on sand than on humus. Thus, the results suggest that interactions between substrate differences and individual movement behaviour may to some extent explain why pine weevils have been observed to feed less frequently on coniferous seedlings planted on mineral soil than on those planted on humus.
Hylobius abietis migrates by flight to new breeding habitats early in summer. Flight speed and height, wind speeds during flight, and flight direction in relation to wind were studied in the field. Flight duration estimates were obtained from flight mill experiments. Using these data dispersal distances of the females in a population were calculated. According to this tentative estimate a majority of the weevils migrated more than 10 km, and some as far as 80 km, during the entire flight period. Hylobius abietis migre par vol vers de nouveaux habitats tt en t. La vitesse et la hauteur de vol, la vitesse du vent pendant le vol, et l'orientation du vol en fonction du vent ont t tudies dans la nature. Aprs l'envol de nombreux adultes s'lvent au-dessus des arbres et volent orients dans le sens du vent, ce qui est certainement une adaptation aux dispersions distance par le vent. La vitesse de vol est de 1,9 m/s par rapport celle de l'air. Les captures avec des piges succion ont fourni des indications sur la vitesse du vent pendant le vol; en combinant ces donnes avec les mesures de la vitesse du vol elle-mme, une estimation de la frquence relative des vitesses de disperison a t obtenue.L'estimation de la dure du vol a t obtenue en laboratoire par des expriences avec un moulin de vol. A partir de ces donnes les distances de dispersion des femelles dans une population ont t calcules. Selon ces essais d'estimation, la majorit des insectes migrent plus de 10 kilomtres et certains vont jusqu' 80 kilomtres pendant l'ensemble de la priode de vol.
Adults of Hylobius abietis (L.) (Coleoptera: Curculionidae) were found to locate conifer roots suitable for oviposition by utilizing host volatiles diffusing through the soil. Underground sources of host volatiles were presented to weevils in a laboratory bioassay. A cold-trapping condensate of Scots pine, Pinus sylvestris L., and fractions of it were tested. Various fractions containing host terpenes attracted weevils in the bioassay, but the complete pine condensate caused the highest response. Ethanol was also found to be attractive. Weevils caged underground in the absence of host material did not attract weevils on the surface.
Top-cited authors
Marcel Dicke
  • Wageningen University & Research
M. W. Sabelis
  • University of Amsterdam
Joop J A van Loon
  • Wageningen University & Research
Silvia Dorn
  • ETH Zurich
John Trumble
  • University of California, Riverside