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

Authors:
  • 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)
219
A  ight mill for large beetles such as
Osmoderma eremita (Coleoptera: Cetoniidae)
Glenn F. Dubois
1*
, Philippe Vernon
1
& Hervé Brustel
2
1
1UMR 6553 CNRS, Université de Rennes 1, Équipe PaysaClim,
Station Biologique, F-35380 Paimpont. E-mail: glenn.dubois@univ-rennes1.fr,
philippe.vernon@univ-rennes1.fr
2
Ecole d’Ingénieurs de Purpan, BP 57611, 75 voie du Toec,
F-31076 Toulouse Cedex 3. E-mail: herve.brustel@esa-purpan.fr
* Corresponding author
ABSTRACT
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
INTRODUCTION
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
220
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).
MATERIAL AND METHODS
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)
221
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.
222
Glenn F. Dubois, Philippe Vernon & Hervé Bruste
RESULTS
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.
DISCUSSION
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)
223
to come close to the real dispersal abilities and the scale at which O. eremita uses its
environment (Dubois et al 2008).
ACKNOWLEDGEMENTS
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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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.
Article
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.
Article
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.