Thoracic temperatures in four libellulid dragonflies (Anisoptera: Libellulidae) K. Reinhardtand D. Kempke Institute of Ecology, Friedrich-Schiller University, Dornburger Str. 159, D-07743 Jena, Germany Abstract —- The thoracic temperatures in several dragonflies.Although these measurements Orthetrum cf. caffrum (Burnt.), Trithemis arteriosa were not continued (see below) and we finally (Burnt.), T. dorsalis (Ramb.) and Palpopleura lucia obtained only a few data, we will nevertheless (Dru.) measured in the field. All this small it were spp. belong present sample as may give a rough to the percher type. Their thoracic temperatures impression for later studies ofthermoregulation in between 0.7 and I0.5°C above ambient were tem- these abundant species. We furthermore intend to The blue O. the the and perature. pale cf. caffrumhad a higher add a cautionary note on use of “grab body temperature than the dark blue T. dorsalis. stab” method (STONE & WILLMER, 1989). The thorax temperature was positively correlated Between 11:30 h and 13:30 h local time, drag- to abdomen lengthbut not forewing lengthbetween onflies were captured at the banks of the stream, with similar trend within Trithemis dor- their sites. All but adult species a usually at perch one were male. The salis. only female was captured after she had completed oviposition. After netting, individuals and methods touched their folded taken Study site were directly at wings, the Pretoria of K: During a stay at University, we were out the net and a fine thermocouple (Type able to visit small farmland a stream on private in NiCr, NiAl 0.2 mm) was inserted about 2 to 3 mm the Boekenhoutskloof area (25°33’S 28°29’E), into the thorax, between the 2nd and 3rd pair of approx. 40 km northeast of Pretoria, Republic of legs on oneside ofthe thorax. After touching, the South Africa. measurement was carried out within 5 s. There- On December carried 9, 1995, we out prelimi- after, the needle was wiped dry and the tempera- of the of measured the site. nary measurements body temperature ture was at perch Additionally, Notul. No. December 1999 42 odonatoi, Vol. 5, 4. pp. 41-52, I, the lengthofthe right forewing and the abdomen, as well as the time between capture and measurement were taken. Results and discussion The thoracic temperature of drag- onflies depends on several factors. It is differently regulated in fliers and perchers. Thermoregulatory ability is also age-dependent In (MARDEN et al„ 1996). our investigation we captured only perching adult males. However, we did not measurethe time the indi- vidual had on its or its spent perch Fig. 1. The relationship between body and ambient temperature in duration. preceding patrol flight four African species of libellulid dragonflies.The straight line indi- Thoracic is temperature usually cates body temperature without thermoregulation. positively correlated to ambient temperature (e.g. MAY, 1987: POLCYN, 1994). It For fliers, it is recommended that the time in- correlated solar in terval between and should was not to radiation one odonate capture measurement whereas the exceed 10 because study (MAY, 1987), opposite was true not s of post-flight heating in grasshoppers (SAMIETZ & KOHLER, 1998). (STONE & WILLMER, 1989). For perchers, on We have measured all T presented here within the other hand, there is the danger of evaporative where of solar and 5 is two hours, an interval, a change cooling an interval of s recommended radiation is unlikely in cloudless skies. (STUTT & WILLMER, 1998). In our study it was An optimalbody temperature is especially ad- impossible to stay within this limit. In T. dorsalis vantageous at the time when most of the species the time elapsed between capture and temperature mate. Then, males should always keep their body measurement (range 9.8-30 s) was negatively but the level for take-off correlated the difference be- temperature at necessary to not significantly to females males and ambient approach orarriving (MAY, 1991). tween body temperature (Spearman in All individuals our study had a thoracic tem- rank, r=- 0.72, N=5, p=0.172). The samewas true individuals combined perature (T ) higher than the ambient temperature when all were (r=- 0.38, (T) (Fig. 1). Sample size, thoracic temperature and N=11, p=0.25). We view these results with cau- its difference to the ambient temperature, as well tion due to our small sample size and because of in as body measurements for the male specimens are the contrast results of different investigations shown in Table I. (STONE & WILLMER, 1989). This, together with Table I - Body temperature, elevation above ambient temperature and morphometric measurements of males offour species of libellulid dragonflies. N refers to sample size. Ambient temperatures were in the of29 range to 37.1°C Species N T (°C)(°C) Tth-Ta (K) Forewing Abdomen |hlh lengthlength (mm) lengthlength (mm) 4 ±2.4 4.1-4.1 - 10.5 32.9 1.3 30.9 ±1.5 OrthetrumOrthetrum cf. caffrumcaffmm (Burm.)(Burnt.) 38.4 ± 2.4 10.5 32.9 ± 1.3 30.9 ± 1.5 Trithemis arteriosa (Burnt.)(Burm.) I1 37.8 0.7 27.0 28.028.0 Trithemis dorsalis 6 1.8 2.4-7.92.4 7.9 31.2 ± 1.0 26.126.1 ±± 1.01.0 (Rambur) 6 34.5 ± - ± Palpopleura lucia (Drury)(Drury) I1 32.432.4 3.5 21.2 15.7 Notul. Vol. No. odonatol., 5, 4, pp. 41-52, December I, 1999 43 the direct ofthe have resulted touching wings may badly damagedthat a lethal injury almost certainly in underestimation of the thoracic occurred. To for the an temperature. our knowledge, a figure per- Even from small interest- of our sample size some centage injured individuals has never been re- conclusions be derived. for insect If with 20% ing may Body tempera- ported any species. a figure well unknown ture was positively correlated to the abdomen but or greater mortality, as as an per- also when of sublethal there should not forewing length (Tab. I), individu- centage injuries occurs, als ofall and corrected for be species are pooled are some ethical concern, especially in investiga- the time between and capture measurement (par- tions using larger sample sizes. tial correlation r =0.67, N=9, p=0.025). This was because in — expected, larger species generalrequire Acknowledgementsi KR’s travel was supported a highertemperature forflight (HEINRICH. 1993). by a grant from the Stifterverband fiir die Deutsche The data is show the correla- too scarce to positive Wissenschaft. J. SAMIETZ made helpful com- tion the trend is simi- within onespecies, although ments on the manuscript. lar in T. dorsalis (Spearman rank correlation, r = 0.71, N=6, p=0.11 ). The strong influence of abdo- References - HEINRICH, B„ 1993, The hot- size also the - men may explain why body tempera- -blooded insects. Springer, Berlin-Heidelberg; O. ture was higher in cf. caffrum than in T. dorsa- MARDEN, J.H., G. KRAMER & J. FRISCH, lis rank W=32.0, J. - (Wilcoxon test, p=0.03), although 1996, exp. Biol. 199: 529-533; MAY, the latter is much paler. 1987, Adv. Odonatol. 3: 103-119; - 1991 ibidem The highest thoracic temperature measured was 5: 71-88; - POLCYN, D.M., 1994, Fund. Ecol. 8: - J. & G. that of anovipositing Orthetrum female (42.6°C) 441-449; SAMIETZ, KÖHLER, the time the individual had in: which at same was that 1998, J. Baumgartner, et al. [Eds], Population been flying probably for the longest time before and community ecology for insect management the of and Balkema, Rotterdam; capture, pointing out potentially high cost conservation, pp. 63-73, thermoregulation during oviposition. - STONE, G.N. & P.G. WILLMER, 1989, J.exp. After the - releasing captured individuals, wewere Biol. 143: 211-223; STUTT, A.D. & P. not able to follow them further. Some flew out of WILLMER, 1998, Anim. Behav. 55: 1341-1347. the sight immediately, others escaped into grassy vegetation. Three individuals (21%) appeared so Received 8 December 1998.