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Effect of cold storage on the pupal development of two pollinators, Eristalinus aeneus and Eristalis tenax
Abstract
Eristalinus aeneus (Scopoli) and Eristalis tenax (L.) (Diptera: Syrphidae, Eristalini), are important pollinator species that can be artificially reared and commercialised. To achieve better control over the pupal development time and adult emergence, cold storage techniques are suitable tools. Insects were reared under controlled conditions: 25 ± 1 °C, 50% r.h., and L12:D12 photoperiod. Pupae of both species were stored at 5 °C at the beginning (early treatments) or at the end (late treatments) of their development for various periods of time (5, 10, 15, 20, or 30 days). Development stopped completely at 5 °C in both treatments, but in general, pupae stored at the beginning of the pupal stage provided better results in terms of survival (adult emergence) and quality of the adults (general morphology). The cold tolerance of E. tenax was lower than that of E. aeneus, with their pupal developmental time successfully extended up to 18 and 23 days, respectively, without compromising survival and morphology. The number and types of morphological alterations due to cold storage were recorded.
The patterns and amount of variation in size, shape, and/or life history traits between females and males are fundamentally important to gain the comprehensive understanding of the evolution of phenotypic diversity. In addition, the covariation of phenotypic traits can significantly contribute to morphological diversification and sexual dimorphism (SD). Using linear and geometric morphometrics, 237 Eristalis tenax specimens sampled from five populations were, therefore, comparatively assessed for the variation in sexual size dimorphism (SSD), sexual shape dimorphism (SShD), and life history traits, as well as for trait covariation (ontogenetic and static allometry). Pupal body, adult wing, and body mass traits were analyzed. Female-biased SSD was observed for pupal length, width, and centroid size, adult wing centroid size, mass, wing loading, and wing area. Conversely, pupal length/width ratio, developmental time, and mass were not found to be sexually dimorphic. Next, wing SShD, but not pupal body SShD was revealed, while allometry was found to be an important "determinant of SD" at the adult stage, with only a minor impact at the pupal stage. By comparing the patterns of covariance (based on allometric slope and intercept) between respective body mass and morphometric traits of pupae and adults, greater variation in allometric slopes was found in adult traits, while static allometries of the two stages significantly differed, as well. Finally, the results indicate that changes in the allometric intercept could be an important source of intraspecific variation and SD in drone fly adults.
The drone fly (Eristalis tenax) pollinates many crops and is found almost worldwide. Its successful management as a field-crop pollinator would provide an additional option to augment bee pollination. We reviewed literature to assess their management potential. A literature search was conducted for information on drone-fly abundance across New Zealand crops, pollinator effectiveness, lifecycle-requirements and potential for mass rearing. Relevant literature was then evaluated to assess the feasibility, benefits and limitations of their management. Eristalis tenax is a proven pollinator of pak choi (Brassica rapa spp. chinensis), kiwifruit (Actinidia deliciosa) and onion (Allium cepa), and visits the flowers of several more crops in New Zealand. It readily completes its lifecycle under laboratory conditions when reared on various organic materials. No reviewed studies were identified that showed successful management of populations for the purpose of field-crop pollination. Key challenges for their management as field-crop pollinators include: being able to mass rear them at an appropriate scale; retaining numbers within targeted areas in the field; and ensuring their use does not significantly impact on non-target species and land-user interests.
Chickpea (Cicer arietinum L.) is an important source of food for people worldwide. In the current study, we studied its pollination biology with special reference to floral visitors along with their visitation rate, frequency and pollen load during 2012 and 2013. We also explored the effect of floral visitors on the capsule weight, seed weight, seed numbers, and seed germination. Results revealed three bees, two wasps, five flies, one moth, and three butterfly species on the flowers of chickpea. Apis dorsata, A. florea, Amegilla sp. and Eristalinus aeneus were the major species with 434-474, 223-311, 69-74, and 81-136 individuals, respectively in both years. Floral visitors differed significantly in term of visitation frequency with A. florea as the most frequent visitor (9.13-9.86 visits/flower/5min) followed by E. aeneus (5.43-5.58 visits/flower/5min) and A. dorsata (1.72-2.31 visits/flower/5min) in both years. Similarly, A. florea had statistically highest visitation rate (16.85-19.99 flowers visited/min) followed by E. aeneus (9.73-10.68 flowers visited/min). A. dorsata had significantly higher pollen load on its body (84,629-8,5104 pollen grains) followed by A. florea (64,940-65,135 pollen grains) and Amegilla sp. (64,020-65,120 pollen grains). The open-pollinated flowers had significantly higher capsule weight (0.27 ± 0.01 g), seed weight (0.18 ± 0.01 g), seed numbers (1.67 ± 0.07 seeds) and seed germination (95 ± 1.38%) as compared to flowers deprived of pollinators in cages. The results suggested A. florea, A. dorsata, and E. aeneus could be effective pollinators of chickpea. Hence these three species can be properly utilized on commercial scale to increase crop yield.
Mass rearing for commercial production of high quality beneficial insects is considered as an important tool for biological control programmes worldwide, especially those based on augmentative releases. Low temperature storage is a valuable method for increasing the shelf life of entomophagous insects. Insect predators and parasitoids are used extensively in biological control programmes and, because of this, studies on cold storage started over 90 years ago. The ability to store reared biocontrol agents at low temperatures for certain duration provides an opportunity to accumulate or stockpile sufficient number of entomophagous insects for field release at proper weather conditions and make them available during high demand periods to the concerned farmers. Cold stored natural enemies can be synchronously released in the fields during critical stages of pest outbreaks. Cold storage also helps to keep viable stock of natural enemies when not needed and to minimize laboratory operations by prolonging their survival and delaying eclosion. Cold storage tolerance is highly plastic trait influenced by a range of biotic and abiotic factors experienced before, during and after cold exposure. These factors ultimately affect the development, longevity, fecundity, parasitization, sex-ratio and other fitness parameters along with morphology, behaviour and physiology of entomophagous insects. For the successful implementation of a cold storage project, knowledge of these diverse factors that cause storage and post-storage effects is essential. The potential of cold storage protocols in improving mass rearing and commercial production of bioagents is thus reviewed to access the strategies, innovations, techniques, devices and wisdom involved in the process of cold storage of entomophagous insects worldwide.
With an estimated 6000 species worldwide, hoverflies are ecologically important as alternative pollinators to domesticated honeybees. However, they are also a useful scientific model to study motion vision and flight dynamics in a controlled laboratory setting. As the larvae develop in organically polluted water, they are useful models for investigating investment in microbial immunity. While large scale commercial breeding for agriculture already occurs, there are no standardized protocols for maintaining captive populations for scientific studies. This is important as commercial captive breeding programs focusing on mass output during peak pollination periods may fail to provide a population that is consistent, stable and robust throughout the year, as is often needed for other research purposes. Therefore, a method to establish, maintain and refresh a captive research population is required. Here, we describe the utilization of an artificial hibernation cycle, in addition to the nutritional and housing requirements, for long term maintenance of Eristalis tenax. Using these methods, we have significantly increased the health and longevity of captive populations of E. tenax compared to previous reports. We furthermore discuss small scale rearing methods and options for optimizing yields and manipulating population demographics.
Podisus nigrispinus are bedbug predators that are used as biological control agents of defolating larvae in eucalypt plantations. The mass rearing of natural enemies produces large numbers of insects, but the number of predators produced may not coincide with the timing of the outbreaks of pest populations in the field. The aim of this study was to evaluate the effects of different storage periods on the eggs of P. nigrispinus at low temperatures of 5, 13 and 15°C. The treatments consisted of periods of 5, 10, 15 and 20 days of storage of predator eggs at each temperature indicated. After the different periods of storage, the eggs were removed, and the egg viability, the survival and duration of nymphal instars and the sex ratio of emerged adults were evaluated. Egg storage at 5°C reduced the percentage of hatched eggs, while viability values close to 50% were observed for storage periods of up to 10 days at 13°C and up to 15 days at 15°C. For these treatments, the survival rates of nymphs were similar to those of the control. The different storage periods had no effect on the duration of the nymphal stage or the sex ratio of P. nigrispinus at any of the temperatures. Therefore, the storage temperature of 5°C caused the death of the majority of the embryos, while it is possible to store P. nigrispinus eggs up to 10 and 15 days at 13 and 15°C, respectively. © 2016, Sociedade de Investigacoes Florestais. All rights reserved.
Intra-puparial development of the females of Chrysomya albiceps (Wiedemann) (Diptera, Calliphoridae). The chronology and morphological changes that take place during intra-puparial development of Chrysomya albiceps is described based on 254 specimens reared in the laboratory. Larvae were obtained from the eggs laid by a single female. The pre-pupae were separated according to the reduction of larval length and the degree of pigmentation and sclerotization of the cuticle. After pupation, 10 individuals were fixed in Carnoy's solution and preserved in 70% ethanol, 10 individuals were fixed every 3 hours up to complete the first 24 hours (n = 80), the remaining individuals were fixed every six hours up to the 90th hour (n = 110) when 54 females emerged. The pupae were immersed in 5% formic acid for 48 hours and maintained in 70% ethanol, and then dissected and analyzed. C. albiceps shows four intra-puparial stages, each of which were described and compared with those described for Musca domestica, Calliphora erythrocephala, Sarcophaga bullata, Cuterebra tenebrosa, Oestrus ovis and Dermatobia hominis. Four developmental stages may be described: (1) the larva-pupa apolysis, after three hours; (2) the criptocephalic pupa, after six hours; (3) the phanerocephalic pupa, after nine hours; (4) the pharate pupa, after nine hours. The pharate adult is completely formed after 81 hours.
Aenasius bambawalei Hayat (Hymenoptera: Encyrtidae) is a solitary nymphal endoparasitoid of Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae), an important pest of cotton in Haryana. The present studies on the effect of cold storage on some biological characteristics of A. bambawalei were carried out by storing one-day-old mummies of P. solenopsis (i.e. parasitoid in pupal stage) for 1 to 8 weeks at four storage temperatures viz., 5, 10, 15 and 20°C at 75 per cent relative humidity. Emergence of the parasitoid adults from mummies occurred within first week during storage at 20°C, hence, this temperature was judged unsuitable for cold storage. The parasitoid A. bambawalei could be stored for one week at 5°C and for two weeks each at 10 and 15°C, without any significant effect on emergence, longevity, fecundity and per cent females emerging in F1 progeny. At the above mentioned temperatures and durations these biological parameters of the parasitoid were comparable with the emergence (100%), longevity (19.60 and 33.20 days for males and females, respectively), fecundity (24.60 mealybugs parasitized per female in five days) and per cent females emerging in F1 progeny (63.12%) recorded in the control (27°C).
Insect dormancy responses, in the broad sense of modifications of development, are examined from a general perspective. The range of responses is extraordinarily wide because environments are diverse, different taxa have different evolutionary histories, adaptations are needed for both seasonal timing and resistance to adversity, and not only development but also many other aspects of the life-cycle must be coordinated. Developmental options are illustrated by examining the wide range of ways in which development can be modified, the fact that each individual response consists of several components, and the different potential durations of the life-cycle. The concepts of alternative life-cycle pathways (chosen according to current and likely future environmental conditions) and of active and passive default responses are treated. Also introduced are aspects of variation and trade-offs. Some general conclusions that help in understanding dormancy responses emerge from such an examination. Many options are available (cf. Table 1). The nature of the habitat, especially its predictability, determines the potential effectiveness of many of the developmental options. Any particular set of responses reflects evolutionary history and hence depends on past as well as current environments. It is not necessarily obvious what kinds of selection, especially requirements for timing versus resistance to adversity, explain a particular life cycle. Life-cycle pathways have multiple components, so that components cannot be analyzed in isolation. A given feature, such as delayed development, can have multiple roles. Default responses can be either active (development continues unless signalled otherwise) or passive (development stops unless signalled otherwise), making necessary a broad approach to understanding the action of environmental cues. Even relatively minor effects that fine-tune dormancy responses enhance survival, but may be difficult to detect or measure. Trade-offs are not inevitable, not only when certain resources are surplus, but also because resources in very short supply (constraints) cannot be traded off. Life-cycle components are widely, but not universally, coordinated. These conclusions confirm that the range of dormancy responses is wider, more complex and more integrated than has often been recognized.
Insects are constantly subjected to changes in environmental temperature. Most studies of insect acclimation to low temperature concern seasonal changes that occur over weeks or months in preparation for winter, and, accordingly, most chapters in this volume focus on seasonal cold-hardening. In contrast, during the past 10 years considerable attention has been paid to rapid acclimatory responses to both high (i.e. induction of heat shock or stress proteins (Feder et al., 2002) and low temperature. This chapter summarizes our current understanding of the rapid cold-hardening (RCH) response. When our previous book (Lee and Denlinger, 1991) was being written, the RCH response had only just been described and merited only a few scattered paragraphs. Indeed, at that time it was unclear whether this response was merely a laboratory artifact or a previously unrecognized type of rapid acclimation. Since then, the RCH response has emerged as a highly conserved trait, allowing diverse insect groups to swiftly adjust their physiological state and organismal performance to match even modest changes in environmental temperature. In this chapter, we summarize evidence supporting the ecological relevance and emerging physiological underpinnings of the RCH response. The RCH response protects against a form of non-freezing injury known as cold-shock or direct-chilling injury. Cold-shock injury is well known among microbes, plants and animals, and represents a major obstacle for the successful cryopreservation of many types of cells and tissues (Grout, 1987). Injury is not associated with internal ice formation.
Investigations to identify the pollinator community of insects and its role in onion (Allium cepa L.) pollination were carried out at the research farm. The community of pollinators was composed of two bees (Order: Hymenoptera) and eight true flies (Order Diptera). Among bees, Apis dorsata proved to be an abundant pollinator (2.85±1.57 individuals/25 plants) while among true flies Episyrphus balteatus (Syrphidae) had the maximum abundance of 14.00±4.61 individuals/25 plants. All the insect pollinator species reached peak activity during 10:00 to 12:00 h. Eupeodes corollae (Syrphidae) exhibited the most efficient foraging behavior by visiting 17.14±1.38 flowers in 147.5±8.14 seconds on an umbel. A. dorsata was revealed as the most effective pollinator, however, based on seed setting results for visits by single species over 20 minutes and which produced 506 seeds/umbel/20 minute visit.
Because of its importance as a pollinator and its potential economic usefulness for the biodegradation of organic animal waste, the genetic and phenotypic diversity of the drone fly, Eristalis tenax L. (Diptera: Syrphidae), was studied in both wild and captive populations from southeastern Europe. Wild specimens from a natural protected habitat (with low human impact), field crop habitat (semisynanthropic condition), and intensive pig farming habitat (synanthropic condition) were compared with a laboratory colony reared on artificial media. An integrative approach was applied based on allozyme loci, cytochrome c oxidase I mitochondrial DNA, wing traits (size and shape), and abdominal color patterns. Our results indicate that the fourth and eighth generations of the laboratory colony show a severe lack of genetic diversity compared with natural populations. Reduced genetic diversity in subsequent generations (F4 and F8) of the laboratory colony was found to be linked with phenotypic divergence. Loss of genetic variability associated with phenotypic differentiation in laboratory samples suggests a founder effect, followed by stochastic genetic processes and inbreeding. Hence, our results have implications for captive bred Eristalis flies, which have been used in crop pollination and biodegradation of organic waste under synanthropic conditions.
Desenvolvimento intra-pupal de fêmeas de Chrysomya albiceps (Wiedemann) (Diptera, Calliphoridae) A cronologia e as mudanças morfológicas que ocorrem durante o desenvolvimento intra-pupal de Chrysomya albiceps são descritos com base em 254 espécimes criados em laboratório. As larvas foram obtidas a partir os ovos postos por uma única fêmea. As pré-pupas foram separadas de acordo com a redução do comprimento larval, o grau de pigmentação e esclerotização da cutícula, depois da formação das pupas, 10 indivíduos foram fixados em solução de Carnoy e conservados em etanol 70%, e 10 indivíduos foram fixados a cada 3 horas, até completar as primeiras 24 horas (n = 80), os demais indivíduos foram fixados a cada seis horas até a hora 90 (n = 110), quando 54 fêmeas haviam emergido. As pupas foram imersas em de ácido fórmico a 5% por 48 horas e mantidos em etanol 70%, e então dissecados e analisados. C. albiceps mostrou quatro estágios intra-pupais, que foram descritos e comparados com aqueles descritos para Musca domestica, Calliphora erythrocephala, Sarcophaga bullata, Cuterebra tenebrosa, Oestrus ovis e Dermatobia hominis. Quatro estágios de desenvolvimento podem ser descritos: (1) apólise da larva-pupa, depois de três horas; (2) a pupa criptocefálica, depois de seis horas, (3) a pupa fanerocefálica, depois de nove horas, e a pupa farada após nove horas. O adulto farado está completamente formado após 81 horas.
The alfalfa leafcutting bee Megachile rotundata (F.) is the primary pollinator for alfalfa seed production. Under standard management conditions, the alfalfa leafcutting bee develops to the diapausing prepupal stage under field conditions, after which they are cold-stored at a static temperature until the following spring, when temperatures are raised and development resumes. We have assessed the effects of a fluctuating thermal regime (FTR) during overwintering cold storage, where bees were exposed to a daily 1 h pulse of 20 degrees C, and compared viability and insect quality to bees stored under a static thermal regime. Our results demonstrate that implementing an FTR protocol dramatically increases the survival of cold-stored alfalfa leafcutting bees, effectively extending their shelf-life into the subsequent growing season. These findings could substantially ameliorate significant obstacles that restrict the more widespread use of this important pollinator, such as the biological constraints that restrict its use in early blooming crops, and yearly fluctuations in bee prices that add significant financial uncertainty to end users. This study also strengthens a growing body of evidence that indicates FTR protocols are superior to static thermal regime protocols for insect cold storage.
The alfalfa leafcutting bee, Megachile rotundata (F.), is a solitary, cavity-nesting bee and is the primary pollinator for alfalfa seed production. Bee management practices include cold storage during the prepupal stage. Fluctuating thermal regimes during cold storage increases survival of cold storage and allows a doubling of the cold storage period with no decrease in survival. However, survival, characterized as successful adult emergence, is not qualitative. In this study, we determined whether extended storage affects adult bee respiration or flight physiology. We overwintered bees for a single winter (current management protocol) or for 12 mo longer (extended storage). We used resting and tethered flight metabolic rates and resting critical PO2 (the oxygen partial pressure below which metabolism can no longer be sustained) as indices of adult bee quality. We found no significant differences in body mass, resting or flight metabolic rates, or critical PO2 between the two groups. Together these data indicate that extended storage of M. rotundata produces bees of similar respiratory capacity and flight ability. These findings could increase the use of M. rotundata as an alternative pollinator, allowing for extended storage to time adult emergence with early blooming crops.
Diptera are one of the three largest and most diverse animal groups in the world. As an often neglected but important group of pollinators, they play a significant role in agrobiodiversity and the biodiversity of plants everywhere. Flies are present in almost all habitats and biomes and for many medicinal, food and ornamental plants, pollinating flies guarantee or enhance seed and fruit production. They are important in the natural landscape, in agriculture and in greenhouses, and have recently come into use in the production of seeds for seed banks. The São Paulo Pollinator Initiative, the CBD, and Pollinator secretariats were important starting points in the international recognition of pollinator importance. However, large gaps in our knowledge of the role of Diptera in pollination networks need to be addressed in order to sustain agriculture and to enable appropriate responses to climate change. At this 9 Conference of the Parties we would like to draw attention to the role of often-neglected Dipteran pollinators, to stress their current importance and potential future use as pollinators in agriculture. A case study on flower flies that act as important pollinators, as adults, and major biocontrol agents, as larvae, illustrates their double importance for agriculture.
Reviews data relevant to three topics that are central to biological-control introductions and to identify areas where some progress has been or can be made: 1) what genetic barriers prevent using a natural enemy from one prey/host species against another closely related prey/host species? If barriers exist, how can they be overcome? 2) Does laboratory rearing for biological-control introductions cause maladaptation of field conditions? If so, how can such maladaptation be avoided? 3) Is adaptation after introduction important for establishment and/or control? If so, how can such adaptation be promoted? -from Authors
The abdominal colour pattern of Eristalis arbustorum (L.) shows seasonal variation, with animals emerging in spring being darker than those emerging during summer. One of the most important environmental cues influencing the abdominal colour pattern is developmental temperature. An experiment was carried out to establish which period during the immature stages was important in determining final adult colour pattern. The results indicate a good relationship between the length of the pupal period and both the extent of the paler markings on the abdomen and the grey score of these markings. The length of the larval period did not have any effect on adult colour pattern.
Differential response was noticed when 4 species ofTrichogramma egg parasitoids were stored at 2°, 5° and 10°C for 7 to 49 days. Pupal stage was found to be most appropriate for storage.
Emergence ofTrichogramma achaeae Nagaraja and Nagarkatti andTrichogrammatoidea eldanae Viggiani was greater in comparison toTrichogramma chilonis Ishii andTrichogramma japonicum Ashmead at all 3 temperature regimes. Fecundity and longevity declined drastically after storage of 14 days at 2° and 5°C
and 21 days at 10°C, when removed to room temperature. 10°C was found to be the best temperature for storage up to 49 days.
Une réponse différentielle a été obtenue chez 4 espèces deTrichogramma, parasitoïdes oophages, stockées à 2°, 5° et 10°C pendant 7 à 49 jours. Le stade pupe s'est révélé le meilleur pour le stockage.
L'émergence était plus importante chezTrichogramma achaeae Nagaraja et Nagarkatti etTrichogrammatoidea eldanae Viggiani en comparaison de celle deTrichogramma chilonis Ishii etTrichogramma japonicum Ashmead, aux 3 températures.
La fécondité et la longévité se réduisent considérablement après 14 jours de stockage à 2 et 5°C et après 21 jours à 10°C,
après retour à température ambiante. La température de 10°C est la meilleure pour une durée de stockage allant jusqu'à 49
jours.
Increasing the ability to store mass-reared natural enemies during periods or seasons of low demand is a critical need of the biocontrol industry. We tested the hypothesis that chemicals can enhance long-term cold storage of a predatory mite Phytoseiulus
persimilis Athias-Henriot. The research objective was to determine the effect of cryoprotectant and carbohydrate chemicals on in-storage survival of predators. In-storage survival at 8°C was greater for predators sprayed with glycerol (5%, v/v) or glucose (10% and 20%, v/v) than with water spray controls. After 74 days in the cryoprotectant experiment, predator survival declined to 11.5% in the 5% glycerol treatment and 7.8% in the water spray control. After 88 days in the carbohydrate experiment, predator survival declined to 22% in the 20% glucose treatment and 2% in the water spray control. Although many individuals expired within 50 days in both experiments, a few females survived more than 200 days. This research suggests that select cryoprotectants and carbohydrates have a limited capacity to facilitate long-term storage of P. persimilis.
The Diptera are the second most important order among flower-visiting (anthophilous) and flower-pollinating insects worldwide. Their taxonomic diversity ranges from Nematocera to Brachycera, including most families within the suborders. Especially important are Syrphidae, Bombyliidae, and Muscoidea. Other families, especially of small flies, are less appreciated and often overlooked for their associations with flowers. We have compiled records of their flower visitations to show that they may be more prevalent than usually thought. Our knowledge of anthophilous Diptera needs to be enhanced by future research concerning (i) the significance of nocturnal Nematocera and acalypterate muscoids as pollinators, (ii) the extent to which the relatively ineffective pollen-carrying ability of some taxa can be compensated by the abundance of individuals, and (iii) the role of Diptera as pollinators of the first flowering plants (Angiospermae) by using phylogenetic and palaeontological evidence. Specializations in floral relationships involve the morphology of Diptera, especially of their mouthparts, nutritional requirements, and behaviour, as well as concomitant floral attributes. The South African flora has the most highly specialized relations with dipterous pollinators, but in arctic and alpine generalist fly–flower relations are important in pollination and fly nutrition.
The intra-puparial development of 150 pupae of Eristalinus aeneus (Scopoli, 1763) and Eristalis tenax (Linnaeus, 1758) was analyzed. Individuals were obtained from the sixth laboratory generation kept under artificial rearing conditions at the facilities of the University of Alicante (Spain). The experiment was conducted at 25 ± 1°C temperature, 50 ± 5% relative humidity, and 12:12 hr (L:D) of photoperiod. Groups of 10 pupae were collected every 6 hr over 48 hr, after that period, pupae were collected daily until the adult emergence. They were fixed in 5% formic acid and preserved in 70% ethanol. Fixed pupae were dissected and photographed. The chronology and morphological changes that take place during the intra-puparial development in both species were analyzed and compared. Five phases were observed: prepupa, before 6 hr; cryptocephalic pupa, between 6 and 24 hr; phanerocephalic pupa, between 24 and 30 hr; pharate adult, after 30 hr; and the adult imago, restricted to the very end of the development process just before adult emergence. In total, the intra-puparial development lasted 189 ± 4 hr in E. aeneus and 192 ± 3 hr in E. tenax, with the pharate adult the longest phase (some 81% of the total developmental time). These data can be used to develop accurate cold storage protocols during artificial rearing of both pollinator species, avoiding critical events during the development and increasing survival.
The importance of eristaline flies (Diptera, Syrphidae, Eristalini) as pollinators in natural ecosystems and for agricultural crops is well known. However, in‐depth studies on the life cycle of most of these species have yet to be carried out. The aim of this research was to study the life cycle of Eristalis tenax (Linnaeus, 1758) and Eristalinus aeneus (Scopoli, 1763) in order to improve the current rearing system employed at the University of Alicante. The results were analysed using the age‐stage, two‐sex life table method. As one of the main results, the mean duration of the life history of E. tenax and E. aeneus was 46.06 and 65.12 days (d), respectively. The most critical step for both species was found at the beginning of the larval stage (first instar), when the highest mortality was recorded. Population parameters were also analysed and compared. The intrinsic rate of increase (r), the finite rate of increase (λ), the net reproductive rate (R0) and the mean generation time (T) were 0.09 (d−1), 1.09 (d−1), 42.11 offspring and 40.97 d, in the case of E. aeneus and 0.05 (d−1), 1.05 (d−1), 23.13 offspring and 59.23 d, in the case of E. tenax. These results indicate that the current rearing system is more efficient for E. aeneus, which displays a faster population growth. However, some modifications need to be implemented to improve the production of E. tenax.
Exorista larvarum (L.) is a tachinid parasitoid native to the Palearctic region, known as an antagonist of lepidopterous defoliators. This species is suitable to be cultured in vitro, and yields of fecund adults, approaching those usually attained in host larvae, have been previously achieved on artificial media. Direct oviposition by E. larvarum on media has not yet been obtained, and the eggs for the in vitro rearing are routinely removed from parasitized host larvae. However, many eggs are usually laid throughout the cage by captive females and can be retrieved by placing them on artificial media. Storage at low temperatures provides a method for prolonging the development of insects and stockpile them when not needed immediately. We studied the effects of storage at 20 °C (for 5 d or until pupation) or 15 °C (for 5 d or until egg hatching) on the in vitro development of E. larvarum. Lower temperatures were excluded, because previous studies showed a strong negative impact on hatching when the eggs were stored at 5 °C or 10 °C. For the experiments, eggs were removed from hosts and placed on an artificial medium. The results suggested that it is possible to delay the development of the in vitro-reared E. larvarum, which eventually reached the adult stage, although some negative effects on fly quality (i.e., longevity and fecundity) were also observed. Because quality is not an absolute concept, all the situations tested in this study could be appropriate according to the current requirements. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: [email protected]
Developmental studies of necrophagous insects are strongly needed to support medico-legal investigations, because minimum postmortem intervals (minPMI) can be estimated from development data for species collected from a forensic scene together with accurate temperature information from that scene. The life cycle of cyclorrhaphous flies, which include some of the most used forensic indicators, shows an unusual feature as the pupal stage and the subsequent development of the pharate adult take place inside an opaque, barrel-like puparium, formed from the cuticle of the third-instar larva (Fraenkel and Bhaskaran 1973). Although unusual this feature is not unique among insects, or even among Diptera, despite the statement of Proenca et al. (2014). The period from pupariation (i.e., puparium formation) until the emergence of the adult is of special importance for forensic studies, as this period lasts for >50% of the total immature development. However, unlike the larval stage where a quantitative measure of age (e.g., body length) can be modeled in relation to time, the puparium shows virtually no external age-related changes (Amendt et al. 2011). Nevertheless, the puparium can be removed in order to determine morphological markers related to age on the insect inside, which can then be used for simple age estimation. Accordingly, a number of recently published studies (e.g., Pujol-Luz and Barros-Cordeiro 2012, Defilippo et al. 2013, Proenca et al. 2014, Ma et al. 2015) have described age-related morphological landmarks in the intrapuparial development of several forensically important Diptera, chiefly blow flies (Calliphoridae). Our concern has to do with confusion regarding concepts and terminology frequently occurring in these kinds of intrapuparial development studies. It is very likely that much of the existing confusion is related to the wide use of the terms “pupa,” referring to any fly individual during its intrapuparial development (regardless of which …
Pollination and Floral Ecologyis the most comprehensive single-volume reference to all aspects of pollination biology--and the first fully up-to-date resource of its kind to appear in decades. This beautifully illustrated book describes how flowers use colors, shapes, and scents to advertise themselves; how they offer pollen and nectar as rewards; and how they share complex interactions with beetles, birds, bats, bees, and other creatures. The ecology of these interactions is covered in depth, including the timing and patterning of flowering, competition among flowering plants to attract certain visitors and deter others, and the many ways plants and animals can cheat each other.Pollination and Floral Ecologypays special attention to the prevalence of specialization and generalization in animal-flower interactions, and examines how a lack of distinction between casual visitors and true pollinators can produce misleading conclusions about flower evolution and animal-flower mutualism. This one-of-a-kind reference also gives insights into the vital pollination services that animals provide to crops and native flora, and sets these issues in the context of today's global pollination crisis.Provides the most up-to-date resource on pollination and floral ecologyDescribes flower advertising features and rewards, foraging and learning by flower-visiting animals, behaviors of generalist and specialist pollinators--and moreExamines the ecology and evolution of animal-flower interactions, from the molecular to macroevolutionary scaleFeatures hundreds of color and black-and-white illustrations.
The effect of low temperature during cold storage on the survival period, mortality and fecundity of adult Copidosoma varicorne (Nees) was investigated under controlled laboratory conditions of 11.00 ± 1.00°C. Adult longevity was maximum 120 hrs. after 48 hrs. of storage. Specimens stored at 11 ± 1°C temperature increased longevity period which was significant, when compared with control. These studies were carried out during April-June, 1998 to explore the possibility of using C. varicorne as a promising biological control against Shisham defoliator (Dichomeris eridantis Meyr.) in the field including augmentation and innundative release on large scale in future under social forestry programme.
Any temperature below that to which a species is best adapted may be regarded as cold. A brief exposure to cold may have a dramatic effect, but usually the affect is negligible; however, keeping insects at low temperature for longer periods of time always affects their mortality and development, and often other parameters as well. Performance at a low, but constant, temperature is usually different than at temperatures fluctuating around the same average value (see Chapter 9).
Prepupae of the Australian sheep blowfly Lucilia cuprina (Wiedemann) which entered the ground during the summer and early autumn pupated within a few days. However, through late March and early April there was a transition to almost nil pupation. Spring emergence was synchronous amongst individuals which had entered the ground from late March through to October. This suggests that prepupae which did not pupate during autumn were not accruing any developmental increments at that time, and that they were in a state of developmental arrest. Development was also frequently arrested in prepupae placed at 16°C after leaving the food source. Such arrest was markedly more frequent amongst prepupae produced between the autumn and spring equinoxes than in the rest of the year. Since prepupae were deprived of obvious seasonal cues at 16°C, it appears that the overwintering state is at least partly determined in some earlier life stage. However, prepupae placed at 25°C after leaving the food source had uninterrupted development in all seasons. The difference between the responses to 16 and 25°C suggests that temperatures experienced by prepupae themselves are also important in determining the overwintering state.
Eretmocerus corni and Encarsia formosa are considered important natural enemies to be used as biological control agents against Trialeurodes vaporariorum in Argentina. The effect of cold storage on some biological parameters of the pupal and adult stages of these parasitoids and their progeny is studied. Parasitoid pupae were stored 7, 14, 21, and 28 days at 4.5±2 and 11.5±2°C, RH=60–75% in full darkness. For Er. corni, pupal survival was negatively affected when the storage was longer than 7 days at either temperature. Adult emergence time after cold storage was shorter at 11.5°C and decreased significantly with the time of storage. Adult survival 3 days after emergence, sex ratio, first day fecundity, pupal survival of the F1 progeny, and proportion of F1 females were not affected by cold storage. For En. formosa, storage at 11.5°C did not affect pupal survival, irrespective of the storage time, but at 4.5°C the proportion of emerged adults decreased significantly. Adult emergence time was shorter at 11.5°C and this reduction increased significantly with the duration of the storage period. Adult survival 3 days after emergence did not vary among cold treatments. First day fecundity of En. formosa was negatively affected by storage longer than 14 days at either temperature. Cold storage of pupae had no effect on pupal survival of their F1 progeny. Our results suggest that pupae can be kept at 11.5°C for up to 14 days or at 4.5°C for up to 7 days to maintain these parasitoids in suitable condition for release.
The pollinating effects of the drone fly, Eristalis tenax (L.), on greenhouse sweet pepper, Capsicum annuum L., were assessed by measuring fruit characteristics. Individual flowers were exposed to either no insect visits, a restricted number of visits, or a continuous exposure to flies during floral receptivity. A 5% increase in pericarp circumference was observed in fruits obtained from the continuously exposed flower group (18.2 ± 4.5 cm [mean ± SD]) compared with those from the non visited group (17.4 ± 3.6 cm). A shift toward a greater percentage of heavier and wider fruits was observed in both fly-visited flower groups. Fruit weight, circumference, and length were highly dependent on seed set and increased as a function of cumulative visit duration. Although the pollinating behavior of E. tenax on sweet pepper flowers is still unexplained, our results indicate that fly pollination has a significant positive impact on the physical characteristics of pepper fruits.
Formation of the puparium in cyclorrhaphous flies occurs many hours before that of the pupa and should be consistently termed pupariation to distinguish it from the process of pupation. During the part of the 3rd larval stage between end of feeding and pupariation, the larva should be called the postfeeding larva. During the period between pupariation and larval-pupal apolysis, the larva should be called the prepupa. The term cryptocephalic pupa denotes the pupa during the period between larval-pupal apolysis and head evagination. The time between head evagination and the pupal-adult apolysis is an extended period during which the insect closely resembles an exarate (free) pupa in other insect orders. Larvalpupal apolysis occurs well after pupariation, and over a period, and starts anteriorly. Pupal-adult apolysis occurs long after head evagination, and also over a period, but starting posteriorly.
Thripobius javae (Girault) was introduced in 1995 from Israel into Italy to control the greenhouse thrips, Heliothrips haemorrhoidalis (Bouché). Following introduction, successive augmentative releases of this parasitoid gave unsatisfactory and contradictory results, mainly due to the difficulty in synchronising its availability in sufficient number at the time of release. Efficient storage of this biological control agent could improve its current production and use. The effects of different sets of storage techniques at a single temperature and with a combination of different temperatures and instars on several fitness traits (residual developmental time to adult emergence after the end of storage, pupal mortality, longevity with and without hosts and progeny of emerged adults) were evaluated in order to determine the best conditions for storing the parasitoid.For the pupal stage, increasing storage up to 14 days, at 10°C, gave only a moderate reduction (33%) of a modified composite quality index of its fitness. In contrast, when adults were stored for more than 10 days, at 15°C, residual longevity and progeny were reduced significantly. A combination of two temperatures (10 and 15°C) for pupal storage and a combination of pupal (10°C) and adult (15°C) storage had detrimental effects on parasitoid fitness. Temperatures of storage lower than 15 and 10°C had detrimental effects on adults and pupae, respectively.
Eristalis intricarius is a Batesian mimic of bumblebees (Bombus spp.). The thoracic pubescence may be orange or black, but a range of intermediates also occurs. The orange-haired form is recessive to the darker types of pattern (alleles Thor and ThD respectively); variation within the dark-haired category seems largely influenced by environmental factors such as pupal temperature. In samples from northern parts of England there were roughly equal numbers of "orange" and "dark" morphs. These morphs are not specialised mimics of individual models, but have a good general resemblance to several species of bumblebee.
1. The honeybee Apis mellifera is currently in decline worldwide because of the combined impacts of Colony Collapse Disorder and the Varroa destructor mite. In order to gain a balanced perspective of the importance of both wild and managed pollination services, it is essential to compare these services directly, a priori, within a cropping landscape. This process will determine the capacity of other flower visitors to act as honeybee replacements.
2. In a highly modified New Zealand agricultural landscape, we compared the pollination services provided by managed honeybees to unmanaged pollinator taxa (including flies) within a Brassica rapa var. chinensis mass flowering crop.
3. We evaluate overall pollinator effectiveness by separating the pollination service into two components: efficiency (i.e. per visit pollen deposition) and visit rate (i.e. pollinator abundance per available flower and the number of flower visits per minute).
4. We observed 31 species attending flowers of B. rapa. In addition to A. mellifera, seven insect species visited flowers frequently. These were three other bees (Lasioglossum sordidum, Bombus terrestris and Leioproctus sp.) and four flies (Dilophus nigrostigma, Melanostoma fasciatum, Melangyna novae-zelandiae and Eristalis tenax).
5. Two bee species, Bombus terrestris and Leioproctus sp. and one fly, Eristalis tenax were as efficient as the honeybee and as effective (in terms of rate of flower visitation). A higher honeybee abundance, however, resulted in it being the more effective pollinator overall.
6. Synthesis and applications. Alternative land management practices that increase the population sizes of unmanaged pollinator taxa to levels resulting in visitation frequencies as high as A. mellifera, have the potential to replace services provided by the honeybee. This will require a thorough investigation of each taxon’s intrinsic biology and a change in land management practices to ensure year round refuge, feeding, nesting and other resource requirements of pollinator taxa are met.
Cold storage of natural enemies usually involves placing insects under constant subambient temperatures. Even at non-freezing temperatures, a reduction in survival is the norm. Using fluctuating thermal regimes (FTR) instead of constant low temperature (CLT) has shown that mortality due to accumulation of chilling injuries was significantly reduced in Aphidius colemani. Whether this phenomenon can be generalised to other parasitoid species is not known. The aim of this study was to analyse interspecific variation in the ability to tolerate cold storage under CLT (continuous 2°C) versus FTR (daily cycle: 2°C for 22 h and 20°C for 2 h) for various durations (0–20 days). Survival, sex ratio and development of five different Aphidiine parasitoids were analysed: A. colemani, Aphidius ervi, Aphidius matricariae, Ephedrus cerasicola and Praon volucre. A marked interspecific variation in the ability to tolerate cold storage was observed: A. matricariae and A. ervi were most chill tolerant, P. volucre and E. cerasicola had an intermediate chill sensitivity and A. colemani was most chill sensitive. In all species tested, FTR significantly reduced cold-induced mortality. This phenomenon was manifested more in chill-sensitive species as they probably accumulate chilling injuries more rapidly. The sex ratio remained unaffected in all the species. Interspecific variation was also observed in developmental responses to cold storage. Under CLT, time to adult emergence of A. matricariae, A. colemani, A. ervi and P. volucre was temporarily stopped and in E. cerasicola it increased. Under FTR, the short daily intervals at 20°C for 2 h allowed parasitoids to continue development in all the species. Interspecific differences are discussed. This study suggests that positive impact of FTR may apply to a wide range of species.
Eristalis tenax L. and E. intricarius L. are two hoverflies which vary considerably in colour pattern. Whilst much of the phenotypic variation in both species is due to genetic variation at major gene loci, there are interactions with pupal temperature and with age of adult. Low pupal temperatures produce, on average, darker abdominal patterns in E. tenax, although the effect is hard to pick out in natural populations. Changes of pattern with age convert a bimodal autumn population to a unimodal post-hibernation population in the following spring. Hair colour is also made darker by cold treatment. Pupal treatments have a strong effect on hair colouration in E. intricarius. High temperatures inhibit the production of black hairs on the thorax, but not all the genotypes are equally sensitive to temperature. Seasonal fluctuations in colour pattern frequencies are detectable in E. intricarius. In three Eristalis species that have been studied so far, the interactions between genotype, age and temperature operate in quite different ways. The temperature responses may be relevant to theories of thermal melanism, although the colour pattern polymorphisms are, more obviously, examples of Batesian mimicry.
In this study, the impact of acclimation (1 month at 15 °C vs. breeding at 30 °C) and fluctuating thermal regimes (daily transfers from low temperatures to various higher temperatures for 2 h) on the cold tolerance of the tropical beetle, Alphitobius diaperinus Panzer (Coleoptera: Tenebrionidae) was examined. Acclimation increased significantly the duration of survival (Lt50) at a constant 5 °C (7.7 ± 0.3 days to 9.7 ± 0.5 days). Survival of acclimated and nonacclimated beetles increased slightly at alternating temperatures of 5 °C/10 °C or 5 °C/15 °C. When daily transfer to 20 °C was applied, survival (Lt50) was improved markedly (nonacclimated: 15.5 ± 0.7 days, acclimated: 19.6 ± 0.6 days). The higher temperatures may allow progressive repair of injuries, and the effects of chilling may be repaired completely at 25 and 30 °C, a phenomenon recorded here for the first time. It is estimated that the theoretical upper threshold of chill injury (Th) of nonacclimated beetles is 15.1 °C whereas it is shifted down to 11.2 °C in acclimated beetles, which might enable this temperature to allow effective repair of injury.
A programme to collect, import and release into Canada the gypsy moth parasitoid,Ceranthia samarensis (Diptera: Tachinidae) is described. The parasitoid's potential for biological control in Canada is also discussed.
The parasitoid was collected in Europe by exposing experimental gypsy moth larvae in areas where local gypsy moth populations were at low densities. Following field exposure, the host larvae were returned to the laboratory and parasitoids reared from them. This technique has shown thatC. samarensis is the suffers 7–16% hyperparasitism.
From 83–90% of theC. samarensis typically enter diapause as pharate adults within the puparia. Laboratory tests of post-exposure host rearing conditions indicate that constant temperatures disrupt the normal parasitoid diapause and that this effect can not be offset by use of either static long or short photoperiods or natural daylengths.
Shipping and cold-storage procedures for puparia are described. Post-storage time to emergence of adultC. samarensis decreased with longer cold storage periods and with higher post-storage incubation temperatures. Emergence requires 112 degree-days above a threshold of 8°C after a period of at least 8 months cold storage.
Releases of adultC. samarensis into field cages at four locations in southern Ontario are documented. While dissection of host larvae from the field cages has failed so far to demonstrate evidence of parasitism, we remain hopeful that some establishment of the parasitoid has occurred.
Implementation of area-wide pest control programmes using the sterile insect technique (SIT) is fundamentally dependant on the ability to rear large numbers of insects and to precisely release them, often at some distance from the production site. This process of producing purely biological agents for pest control frequently demands that periods of low temperature are utilized to store, stockpile or immobilize the insects to maintain quality and gain economy and effectiveness. Likewise, rearing and maintenance of often numerous laboratory colonies for the purpose of conducting research to develop and improve SIT programmes can also benefit from the use of this technology. Two approaches that can be used to maintain quality and to extend the utility of insects are cryopreservation and dormancy. Using either of these methods to extend the shelf-life of mass-reared or laboratory-cultured insects requires that they closely conform to the physiological and developmental capabilities and characteristics of a particular species. The technical aspects of this conformity are discussed, along with the advantages of using these two approaches for extending insect shelf-life. Both approaches have specific requirements for employment and both yield benefits relating to short- or long-term storage needs.
KEYWORDS cryopreservation, diapause, quiescence, shelf-life, dormancy, mass-rearing, in vitro fertilization
The hypothesis that oxidative stress plays a role in chilling injury in the housefly was investigated by determining the effect of chilling on two important components of the insect's antioxidant defense system: (i) the superoxide anion scavenging enzyme, superoxide dismutase, and (ii) the tripeptide, glutathione, which is significant in maintaining the cellular redox status of the cell. The observations that led to this hypothesis are: (i) the housefly exhibited an U-shaped curve in O2consumption rate during development at 28°C from pupariation to the pharate adult stage when sampled at 24-h intervals and (ii) O2consumption rates of these different age groups prior to chilling was negatively correlated to the time after acute transfer to 7°C required to observe a 50% reduction in adult emergence (LT50s) after their return to 28°C. Superoxide dismutase (SOD) activity changed during this period of development at 28°C in an inverted U-shaped manner and was positively correlated to their LT50s when acutely transferred and stored at 7°C. The SOD activity increased in the 12–24 h and 36–48 h postpupariation age groups at 7 and 10°C compared to the activity prior to chilling (Day 0). The 60–72 h postpupariation group and older showed initial reductions in SOD activity during cold storage when compared to Day 0. Total glutathione (GSH and GSSG) in the different age groups was typically decreased by cold storage. The percentage loss of glutathione in the different age groups after 7 days at 7°C was negatively correlated to their LT50s at 7°C. The significance of these changes in SOD activity and glutathione levels to chilling injury in the housefly is discussed.