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A flight mill for large beetles as Osmoderma eremita (Coleoptera: Cetoniidae)

  • Université de Toulouse Ecole d'ingénieurs de Purpan

Abstract and Figures

Dispersal is a key characteristic in species conservation as a major process involved in metapopulation viability. This process is infl uenced by extrinsic (e.g. air temperature) and intrinsic (e.g. body condition) factors. Flight mill experiments are an indirect and simple approach allowing comparative studies on flying species. Different steps of flying dispersal, such as take-off or flight itself, may be closely studied thanks to flight mills. After a short review of diff erent types of flight mills used in various taxa, we present here a flight mill designed for large beetles such as Osmoderma eremita (Coleoptera: Cetoniidae). This flight mill is suitable for the study of flight propensity and abilities of this endangered species, reputed to present low rate and short range dispersal.
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A  ight mill for large beetles such as Osmoderma eremita (Coleoptera: Cetoniidae)
A  ight mill for large beetles such as
Osmoderma eremita (Coleoptera: Cetoniidae)
Glenn F. Dubois
, Philippe Vernon
& Hervé Brustel
1UMR 6553 CNRS, Université de Rennes 1, Équipe PaysaClim,
Station Biologique, F-35380 Paimpont. E-mail:,
Ecole d’Ingénieurs de Purpan, BP 57611, 75 voie du Toec,
F-31076 Toulouse Cedex 3. E-mail:
* Corresponding author
Dispersal is a key characteristic in species conservation as a major process involved in metap-
opulation viability. is process is in uenced by extrinsic (e.g. air temperature) and intrinsic (e.g.
body condition) factors. Flight mill experiments are an indirect and simple approach allowing
comparative studies on  ying species. Di erent steps of  ying dispersal, such as take-o or  ight
itself, may be closely studied thanks to  ight mills. After a short review of di erent types of  ight
mills used in various taxa, we present here a  ight mill designed for large beetles such as Osmoderma
eremita (Coleoptera: Cetoniidae). is ight mill is suitable for the study of  ight propensity
and abilities of this endangered species, reputed to present low rate and short range dispersal.
Keywords: Cetoniidae, Conservation, Dispersal, Flight abilities, Tethered  ight
Dispersal is a key characteristic in species conservation as a major process involved in
metapopulation viability (Ranius 2006). is process is in uenced by extrinsic (e.g. air
temperature) and intrinsic (e.g. body condition) factors (Ims and Hjermann 2001).
J. Buse, K.N.A. Alexander, T. Ranius, T. Assmann (Eds) 2009
S B -      E    
Proceedings of the 5th Symposium and Workshop on the Conservation of Saproxylic Beetles, pp. 219-224.
Pensoft Publishers
So a–Moscow
Glenn F. Dubois, Philippe Vernon & Hervé Bruste
Flight mill experiments are a simple approach allowing descriptive studies on the
factors in uencing ight, and allowing also comparative studies on  ying species. Di er-
ent types of  ight mills were used for various small insect taxa, e.g. for Cicadulina storeyi
(Homoptera: Cicadellidae, Riley et al. 1996), Lygus lucorum (Heteroptera: Miridae, Lu
et al. 2007), Pectinophora gossypiella (Lepidoptera: Gelechiidae, Wu et al. 2006), Musca
domestica (Diptera: Muscidae; Cullis and Hargrove 1972), Dendroctonus pseudotsugae
(Coleoptera: Scolytidae, Smith and Furniss 1966), Oplocephala haemorrhoidalis and
Bolitophagus reticulatus (Coleoptera: Tenebrionidae, Jonsson 2003). e smallest insects
studied with  ight mills were Culicidae (Diptera, Rowley et al. 1968) but, to our knowl-
edge, no  ight mills were used for insects weighing several grams.
We present here a mill we designed for large beetles such as Osmoderma eremita
(Coleoptera: Cetoniidae), an endangered species which is reputed to present low rate
and short range dispersal (Hedin et al. 2008) but in which unexpected  ying movement
length was recently measured (Dubois and Vignon 2008).
Constructing a  ight mill for large insects of several grams implied to resolve the problem
of the noticeable mass of the individuals that is likely to cause frictions and deformations
of the device during the  ight. We constructed a prototype of  ight mill that would
allow the avoidance of such frictions and deformations (Fig. 1). e masterpiece of
the device was a ball bearings (internal Ø = 8 mm, external Ø = 22 mm, thickness = 7
mm; Fig. 1a, C) that annihilated frictions on the pivot caused by the lever e ect of the
Figure 1. Flight mill (1a) and detail of the  xation system (1b): A) base; B) pivot; C) ball bearings;
D) arm; E) counterweight; F) needles; G) emalene foam.
A  ight mill for large beetles such as Osmoderma eremita (Coleoptera: Cetoniidae)
arm. e ball bearings had a precision rate number of 7 (Annular Bearing Engineering
Committee scale system). e pivot (Fig. 1a, B) was an aluminium rod (length = 600
mm, Ø = 8 mm) that was stuck in a heavy wooden base (300 x 300 x 20 mm; Fig. 1a, A)
to avoid vibrations. e aluminium arm of the mill (500 x 11 x 2 mm; Fig. 1a, D) was
only vertically  exible owing to its  attened shape. It was lightened by 31 holes (Ø = 6
mm) and fastened to the ball bearings. Insects were glued with cyanoacrylate by their
pronotum to emalene foam sticks (50 x 5 x 5 mm; Fig. 1b, G; Fig. 2). Two needles were
glued with cyanoacrylate at one end of the arm (Fig. 1b, F) for an easy and precise  xing
of insects equipped with emalene foam. Foam equipped insects were  xed so that their
body stayed horizontally before the  ight. A counterweight of adhesive paste was  xed
at the other end of the arm (Fig. 1b, E).
To test the mill, we used willing to  y individuals of O. eremita (n = 5, m = 1.43
g ± 0.05 SE, Min = 1.38 g, Max = 1.60 g) and of Oryctes nasicornis (Coleoptera: Dy-
nastidae; n = 5, m = 3.59 g ± 0.39 SE, Min = 2.40 g, Max = 4.83 g). To activate  ight,
we used tarsal re ex (White et al. 1983), blows (Boiteau, 2002) and we put a 250 W
mercury vapour lamp 30 cm above the centre of the mill. Tests were made at 23°C. We
made one trial per individual (i.e. ve trials per species) and we calculated the maximum
speed of rotation (i.e. maximum tethered  ight speed) and  ight duration with a bike
milometer after having put the magnet of the milometer on the arm and the sensor of
the milometer on the pivot.
Figure 2. Front view of O. nasicornis (2a) and of O. eremita (2b)  ying on the mill.
Glenn F. Dubois, Philippe Vernon & Hervé Bruste
All the beetles we used managed to take o , to  y and to provoke device rotation (Fig.
2). e maximum speed of rotation was 6.80 km/h ± 0.58 SE in O. eremita (up to 8.55
km/h) and 11.05 km/h ± 0.38 SE in O. nasicornis (up to 12.05 km/h). e maximum
ight duration was 19 min for O. eremita and 68 min for O. nasicornis.
e maximum speeds we measured are consistent with those observed on the free
ights of O. eremita and O. nasicornis (personal observations, GFD and HB) and
therefore it is not likely that the device would drastically modify  ight speeds. e
long non-stop  ight we obtained (more than one hour for O. nasicornis) would also
demonstrate the viability of the device. Nevertheless, tethered  ight experiments may
produce results which show longer or shorter  ight duration ability than is actually
the case for the species being tested, and it is thus preferable to use data from such
experiments in comparative studies.
Since we found it to work well for individuals weighing 1.38 g to 4.83 g, the
device we propose is suitable for the study of  ight abilities of large holarctic beetles,
of which O. nasicornis is one of the heaviest species. It is particularly suitable for ex-
periments on O. eremita, which never weigh more than 5 g. Since the device worked
during some preliminary tests with individuals of Cetonia aurata weighing less than
1 g, it is also expected to work with the smallest individuals of O. eremita. We do not
know the maximum size and weight the mill would function with, but we assume that a
longer radius and a heavier (more stable) device would be needed for the largest species.
Tethered  ight experiments should provide valuable data for determination of some
dispersal-relative life history traits. Once connected to a data acquisition system, they
may be used to measure e.g. the propensity to take o and to  y (Boiteau 2002), and to
measure some  ight parameters such as the number of  ights, the  ight distance and
duration, the resting time, or the maximal and average speed. Interesting extrinsic and
intrinsic factors (Ims and Hjermann 2001) which should be controlled when studying
ight abilities of O. eremita with a  ight mill may be e.g. air temperature, sunlight
intensity, wind speed (extrinsic factors) and sex, sexual maturation, ight muscle size
(Jonsson 2003) or body condition (intrinsic factors). us, intraspeci c or interspeci c
comparative studies could be performed to analyse dispersal processes. Interspeci c
comparisons could be made to discuss, for instance, the ecological signi cance of  ight
abilities when determining resource quality (Jonsson 2003). e maximum non-stop
ight duration (19 min) we obtained for O. eremita indicates physiological abilities that
cannot be achieved in natura using radio-tracking methods (maximum single  ight
distances: 160 m, Hedin et al 2008; 300 m, Dubois and Vignon 2008). Controlling
extrinsic and intrinsic factors during  ight mill experiments may help researchers
A  ight mill for large beetles such as Osmoderma eremita (Coleoptera: Cetoniidae)
to come close to the real dispersal abilities and the scale at which O. eremita uses its
environment (Dubois et al 2008).
We owe special thanks to Olivier Martin (ISATIS Environnement) for valuable help in
individual collecting of O. eremita and to Daniel Sauvard (INRA UR Zoologie Forestière)
for help in device improvement. We are grateful for the permissions that were granted
to us by the prefectural o ce of Sarthe department (permission n°07-2841 of the 6th
of June 2007) to carry out collecting of O. eremita.  is work was supported by the pre-
fectural o ce of Sarthe department, the DIREN Pays de la Loire, the General Council
of Sarthe department and by the company Co route.
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Cetoniidae) in French chestnut orchards. In: Vignon V and Asmodé J-F (Eds.) Proceedings
of the 4th Symposium and workshop on the conservation of saproxylic beetles, held in
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Dubois GF, Vignon V, Delettre YR, Rantier Y, Vernon P and Burel F (2009). Factors A ecting
the Occurrence of the Endangered Saproxylic Beetle Osmoderma eremita (Scopoli, 1763)
(Coleoptera: Cetoniidae) in an Agricultural Landscape. Landscape and Urban Planning
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of mosquito  ight. Annals of the Entomological Society of America 61: 1507-1514.
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tethered  ight in healthy and infected Magicicada septendecim L. Oecologia 57: 281-286.
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gossypiella Saunders (Lepidoptera: Gelechiidae). Environmental Entomology 35: 887-893.
... A flight mill was used to measure the flight parameters for each individual (technical description in Dubois et al. 2009a). Its rotating arm, which had a radius of 24 cm, was articulated with the main axis by low friction ball bearings. ...
... Even if some LDD may occur in some conditions in nature in O. eremita and if the flight distances we measured corroborate some previous performance predictions (Antonsson 1998), our estimates cannot be used, for the moment, to define the spatial extent of landscape scale habitat management. Nevertheless, the species seems to have poor dispersal capacity in comparison with the dispersal capacity of other saproxylic beetles measured previously in tethered flight experiments (with flight mills), e.g. with the corticolous Dendroctonus pseudotsugae Hopkins (Coleoptera: Curculionidae) that flew up to 20 km (Williams and Robertson 2008), with the endangered mycophagous Oplocephala haemorrhoidalis F. (Coleoptera: Tenebrionidae) that flew up to 29 km (Jonsson 2003) or with the saproxylophagous Oryctes nasicornis L. (Coleoptera: Dynastidae) that flew up to 11 km (Dubois et al. 2009a). Sex and body condition interaction on flight capacity and pre-flight behaviour Flight capacity measured on a mill might be biased compared to field data, but tethered flight experiments provide a simple comparative method to detect flight variability under similar conditions for all individuals. ...
Full-text available
The dispersal capacity of rare and endangered insect species has rarely been estimated even though it is essential for their management. For these species, laboratory based experiments are considered more appropriate for determining dispersal capacity as well as the factors influencing it. We aimed to characterize dispersal capacity of the endangered saproxylic beetle Osmoderma eremita (Scopoli, 1763) (Coleoptera: Cetoniidae). We studied the influence of sex and body condition on several parameters of dispersal (seven parameters of flight capacity measured in laboratory and pre-flight behaviour observed in the wild). Tethered flight experiments, conducted on 30 individuals collected in several regions of France, revealed: (1) maximal single flight distance of 1,454m and maximal total flight distance of 2,361m; (2) higher flight capacity in females than males; (3) flight speed and take-off completion decreasing with increasing body condition only for females. Additionally, 32 individuals displaying pre-flight behaviour in the wild showed similar interacting influences of sex and body condition: females initiating pre-flight behaviour had lower body condition than males. Thus, males and females have different dispersal strategies. We propose that body condition influences on dispersal capacity should be considered for species conservation by, for instance, managing adult food resources at the landscape scale and need to be taken into account in introduction programmes.
... All images used with permission. (Schumacher et al. 1997), glass capillary tubes (Atkins 1961, Smith andFurniss 1966), balsa wood (Schoenleter et al. 1970, Nilssen and Anderson 1995, Tsunoda and Moriya 2008, spring or feeler gauge steel (Hocking 1953, Koerwitz and Pruess 1964, flat brass or aluminum (Chambers and O'Connell 1969, Resurreccion et al. 1988, Dubois et al. 2009), copper wires (Cheng et al. 1997, Wong et al. 2018, carbon rods (Bradley and Altizer 2005, Lopez et al. 2014, Barkan et al. 2018, and stainless steel hypodermic tubing (Chambers et al. 1976, Wales et al. 1985, Beerwinkle et al. 1995, Jones et al. 2010. Unusual materials like cereal stems, bamboo, and guitar wire have even been used (Dybovskiy 1970, Stewart and Gaylor 1994, Moriya 1995. ...
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Dispersal is a key component in the population ecology and dynamics of insects and remains one of the most difficult and intractable ecological processes to study in the field. As a consequence, many researchers have looked to laboratory methods for investigating the myriad factors that govern and impact an insect’s ability to move within its environment. A key tool in this effort since at least the early 1950s has been the insect flight mill. Nearly 260 studies have been published using flight mills covering 214 species in 61 families and 9 orders. This review explores the methodology and technology of tethered flight in insects using flight mills. The goal is to provide the reader with a historical context of the approach, an understanding of the available tools and technology, background on how best to apply these tools through a comparative lens, and to summarize the wide breadth of factors that have been explored to further our knowledge of insect flight behavior. Overall, it is hoped that the interested reader will understand the limits and benefits of flight mills and will know where to find the resources, and perhaps collaborators, to pursue this line of study.
... We designed a flight mill to test the flight capacities of hornets, drawing on previously described models ( [28]; Fig 1). The base of the flight mill was a cast iron support stand (Fisher Scientific 6693C) into which we screwed a threaded shaft (10 mm in diameter, 10 cm in height). ...
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The invasive yellow-legged hornet, Vespa velutina nigrithorax Lepeletier, 1836 (Hymenoptera: Vespidae), is native to Southeast Asia. It was first detected in France (in the southwest) in 2005. It has since expanded throughout Europe and has caused significant harm to honeybee populations. We must better characterize the hornet’s flight capacity to understand the species’ success and develop improved control strategies. Here, we carried out a study in which we quantified the flight capacities of V. velutina workers using computerized flight mills. We observed that workers were able to spend around 40% of the daily 7-hour flight tests flying. On average, they flew 10km to 30km during each flight test, although there was a large amount of variation. Workers sampled in early summer had lower flight capacities than workers sampled later in the season. Flight capacity decreased as workers aged. However, in the field, workers probably often die before this decrease becomes significant. During each flight test, workers performed several continuous flight phases of variable length that were separated by rest phases. Based on the length of those continuous flight phases and certain key assumptions, we estimated that V. velutina colony foraging radius is at least 700 m (half that in early summer); however, some workers are able to forage much farther. While these laboratory findings remain to be confirmed by field studies, our results can nonetheless help inform V. velutina biology and control efforts.
... A flight mill (based on Dubois, Glenn, Vernon, & Brustel, 2009) was constructed to test flight capacities of ALB ( Figure 1). An arm was plugged on a vertical axis using a miniature ball bearing to minimize friction. ...
The Asian Long-horned Beetle (ALB) is a highly polyphagous species invasive in North America and Europe. This species has been reported to have low dispersing potential, but long-distance dispersal could occasionally happen. We conducted a preliminary study on laboratory-reared adults from invasive populations to measure the flying potential of beetles using computer-linked flight mills. Under standardized conditions, ALB was capable of flying over longer distances than previously described. The highest distance recorded over an adult lifespan outreached 14 km. Flight mill method is therefore useful to estimate the maximum physiological flight abilities of the species that should be taken into account to improve management of invasive populations.
... Krikken (1984) has previously raised doubts about the monophyly of Trichiini (s.l.), pointing to a lack of synapomorphic characters that would unite the tribes Cryptodontini, Incaini, Osmodermatini, Platygeniini, and Trichiini in a single clade. Although the position of Osmoderma in the BI tree is congruent with the morphology of elytra articulation and flight mode (Dubois et al., 2009;pers. observ.), the position of Inca, Myodermum, and Diploa is not, possibly due to long branch attraction. ...
Rose chafers (Cetoniinae) are a large group of flower visitors within the pleurostict Scarabaeidae that are characterized by their distinctive flight mode with nearly closed forewings. Despite their popularity, this is the first study to use molecular data to infer their phylogenetic relationships. We used partial gene sequences for 28S rRNA, cytochrome oxidase I (cox1) and 16S rRNA (rrnL) for 299 species, representing most recognized subfamilies of Scarabaeidae, including 125 species of Cetoniinae. Combined analyses using maximum parsimony, maximum likelihood and Bayesian inferences recovered Cetoniinae as monophyletic in all analyses, with the sister clade composed of Rutelinae and Dynastinae. Rutelinae was always recovered as paraphyletic with respect to Dynastinae. Trichiini sensu lato (s.l.) was recovered as a polyphyletic clade, while Cetoniini s. l was recovered as paraphyletic. The inferred topologies were also supported by site bootstrapping of the ML trees. With the exception of Cremastochelini, most tribes of Cetoniinae were poly- or paraphyletic, indicating the critical need for a careful revision of rose chafer classification. Analysis of elytral base structural (including 11 scored characters) in the context of phylogeny, revealed a complex, concerted and rapid transformation of the single trait elements linked to a modified flight mode with closed elytra. This appears to be unlinked to the lateral sinuation of the elytra, which originated independently several times at later stages in the evolution of the group.
... A flight mill as described in the work of Dubois et al. (2009), designed to test the flight potential of Osmoderma eremita (Scopoli) (Coleoptera: Cetoniidae), was adapted to R. ferrugineus with the addition of a computer-monitored system (fig. 1). ...
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The red palm weevil, Rhynchophorus ferrugineus (Olivier) (Coleoptera: Dryophthoridae), native to tropical Asian regions, has become a serious threat to palm trees all over the world. Knowledge of its flight potential is vital to improving the preventive and curative measures currently used to manage this pest. As R. ferrugineus is a quarantine pest, it is difficult to study its flight potential in the field. A computer-monitored flight mill was adapted to analyse the flying ability of R. ferrugineus through the study of different flight parameters (number of flights, total distance flown, longest single flight, flight duration, and average and maximum speed) and the influence of the weevil's sex, age, and body size on these flight parameters. Despite significant differences in the adult body size (body weight and length) of males and females, the sex of R. ferrugineus adults did not have an influence on their flight potential. Neither adult body size nor age was found to affect the weevil's flying abilities, although there was a significantly higher percentage of individuals flying that were 8-23 days old than 1-7 days old. Compared to the longest single flight, 54% of the insects were classified as short-distance flyers (covering <100 m) and 36 and 10% were classified as medium- (100-5000 m) and long-distance (>5000 m), respectively. The results are compared with similar studies on different insect species under laboratory and field conditions.
Saproxylophagous insects are an important part of the biodiversity of temperate forests and play a fundamental biogeochemical role being involved in the degradation of dead wood. The European saproxylic complex is now disrupted by anthropogenic changes in forests. Many species of this complex are endangered and their conservation necessitates understanding the causes of their vulnerability. We studied the ecology of a cavity-dwelling saproxylophagous beetle, Osmoderma eremita, a species that is becoming scarce throughout its range and has low dispersal capacities. We monitored its populations by capture-recapture and radio-tracking. Additional measures were undertaken in the laboratory (flight-mill). Our objectives were to explain the distribution of the species in an agricultural landscape, to study its dispersal capacities and to analyze its other demographic characteristics. We have revealed the influence of openness and of the density of microhabitats on the presence of the species, with a preference for areas that have suffered the smallest loss of habitat within 60 years. We measured dispersal capacities that were three times greater than those observed in nature. The capacities of females were related to their condition. The demographic analysis revealed biased sex-ratios depending on population and year. We have demonstrated the role of sex in the demography of the species, a factor which should take place in viability analyses. Such analyses enable to propose conservation measures for O. eremita adaptable to other saproxylophagous species.
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The Hermit beetle, Osmoderma eremita (Coleoptera: Cetoniidae) is an emblematic and endangered species of the saproxylic communities. A monitoring programme was planned for ten years in France (Sarthe department) to gain a best understanding of the local conservation stakes of this protected species. The monitoring includes capture - mark - recapture and radio-tracking methods to analyse the occupancy rate of hollow trees, the size of the populations and the dispersal behaviour of the adults. We present in particular the data collected during the first season of radio-tracking of this programme. No dispersal was observed with capture - mark - recapture but this method brought out the adults emerged in small numbers (one to seven adults per tree). Radio-tracking enabled the observation of the movements of one individual. The range of these movements reached almost 700 m. Such a distance had never been observed and could lead to new insights about the dispersal abilities of O. eremita. Furthermore, this observation led us to first considerations regarding the management of chesnut orchards, a key habitat for conservation of O. eremita in Sarthe department (France). Particularly, we emphasized the potential positive effect of keeping grafted trees producing drupes and the potential negative effect of coppices on the efficiency of individual movements.
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A flight mill is described which permits the automatic measurement of flight duration, speed, periodicity and wing-beat frequency.(Received August 20 1971)
The successful flight takeoff of untethered Colorado potato beetles, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), consists of a strongly sequenced set of behaviors beginning with site location and followed by expansion of the hind wings, rising of the mesothoracic legs, air lifting, and rising of the prothoracic legs, leading to a low angle flight departure. A series of ablation experiments demonstrated that the antennae, the elytra, the mesothoracic legs, and the prothoracic legs all play a significant role in determining the percentage of successful flight takeoffs, as well as the proportion of upward versus downward liftoffs. Flight takeoff of tethered L. decemlineata is positively stimulated by head winds of increasing speeds up to speeds of slightly more than 5.5 m/s. The absence of tarsal contact does not stimulate flight takeoff in L. decemlineata, but tarsal contact interrupts flight. The flight characteristics during liftoff indicate that this species is an in-phase functionally four-winged insect, probably with the hind pair of wings leading the wing beat. Among Coleoptera, the takeoff of L. decemlineata was found to belong to the Melolontha type (classification of Schneider 1975), because the elytra are active.
Specifications and construction of an automatically recording insect flight mill are described. Revolutions of individual flight mills are recorded, by means of photocells, on electric counters.
The potential and propensity in flight of Pectinophora gossypiella (Saunders) in the laboratory were measured using a 32-channel, computer-monitored flight-mill system. Females flew significantly farther within a 72-h flight period than did males. The mean accumulated flight distance and flight duration of 1-d-old female individuals in a tethered-flight test were 41.25 ± 7.76 km and 23.87 ± 2.55 h, respectively, whereas for male individuals, the same parameters were 23.46 ± 2.13 km and 14.12 ± 1.12 h. The flight ability of adults was significantly positively correlated with pupal weight. The flight activity of unmated pink bollworm moths increased daily from the time of eclosion, reaching a peak at 3≈5 d and reducing gradually. All the moths could fly normally at 16≈36°C; however, the optimum temperature for flight ranged from 24 to 28°C, whereas the optimum relative humidity ranged from 75 to 90%.
A flight mill system is described for the quantitative assessment of mosquito flight performance under controlled laboratory conditions. The system includes a device which insures uniform attachment and orientation of mosquitoes to flight mill arms. Attachment and orientation of the mosquito prior to flight are second in importance only to the over-all efficiency of the flight mill itself. Data-recording equipment accurately measures the distance flown, the flight duration, and the speed of mosquito flight.
1. Life-history traits associated with colonisation ability were compared in the threatened tenebrionid beetle Oplocephala haemorrhoidalis and its common relative Bolitophagus reticulatus. Both species feed and breed exclusively in fruiting bodies of the wood-decaying fungus Fomes fomentarius. 2. The presence and status of flight wings, flight muscles, and mature eggs were determined by dissection. Flight willingness was studied in a field experiment, and flight duration in a flight-mill experiment. 3. Females of O. haemorrhoidalis had fewer but larger eggs in their abdomen than B. reticulatus females. 4. All beetles of both species had fully developed flight wings but a larger proportion of B. reticulatus than O. haemorrhoidalis had developed flight muscles. 5. Bolitophagus reticulatus was more willing to take off than O. haemorrhoidalis, however both species, especially O. haemorrhoidalis, were powerful fliers, with many individuals being able to fly several kilometres. Oplocephala haemorrhoidalis tended to make few flights of long duration whereas B. reticulatus made several, but mostly shorter, flights. 6. The results indicate that B. reticulatus has a suite of life-history traits that makes it better adapted than O. haemorrhoidalis to exploit the scattered trees with fruiting bodies present in managed forests. This may explain why O. haemorrhoidalis is restricted primarily to sites with a high density of suitable substrates that have been available continuously for a long time.
Flight mills are commonly used to assess the relative flight performance of migratory insects, but uncertainties about the rate of energy expenditure on the mill mean that absolute estimates of flight endurance are not usually attempted. In this paper we describe how we measured the power delivered to a lightweight flight mill by tethered Cicadulina storeyi China leafhoppers (Homoptera: Cicadellidae), and compared this to estimates of the power they use to maintain free flight. Our results showed that the leafhoppers were generating more than 0.90 W of mechanical power when on the mill, and that they probably have 3–4 W available for free flight. We conclude that whilst flying on the mill, the insects were generating at least 20–30% of the mechanical power needed for free flight, and that this percentage may have been significantly higher.
Flight capabilities of healthy and fungus infected Magicicada septendecim L. (Homoptera: Cicadidae) were compared using 3 complementary techniques: 1) observations of spontaneous flights, 2) field-tested flights, and 3) tethered flights in which endurance was measured. Spontaneous flight distances are much lower than those obtained on field tested fliers. While healthy individuals flew significantly greater distances than did individuals bearing conidia or resting spores of the fungus, Massospora cicadina Peck, the two groups-healthy versus conidia and resting spores pooled-did not differ in flight speed or flight endurance. The magnitude of each of the 3 flight indicators is much lower than those of most dispersing insects, suggesting that this periodical cicada species is a relatively poor disperser.Nevertheless, and contrary to the results of one published study, cicadas flew long distances in single flights, also they often took many flights. Our data help to explain how periodical cicadas can invade new, sometimes distant, habitat each generation. Since infected individuals have both the speed and the endurance of healthy individuals, we conclude that the conspicuous absence of the fungus from early successional, manmade, and second growth habitat is due either to the inability of resting spores of this fungus to survive in recently plowed or fertilized soils or to an intrinsic aversion to flight of infected individuals.