The functions of wingclapping in the Calopterygidae (Zygoptera)

The occurrence and function of wingclapping have been examined in the field and in the laboratory in Calopteryx splendens, C. xanthostoma, C. virgo and C. haemorrhoidalis. Wingclapping, which occurs commonly after flight, involves a slow wing depression by up to 160° (mean duration 735 ms; maximum, 1300 ms), followed by a rapid elevation (mean duration 157 ms; maximum, 200 ms), with a mean ratio of 4.68:1.0. In the field, wingclaps were observed after 33.6% of all flights in C. splendens. at 24-25“C (ambient shade temperature), 5 times more commonly in males than in females; they occurred after 32% of all flights in C. xanthostoma at 30°C and after 80% of all flights in C. haemorrhoidalis at 30°C, with a similar proportion in each sex. – In the laboratory at 30"C wingclapping commonly followed tethered flights, and sometimes also walking and grooming. The number of wingclaps was not correlated with the duration of the preceding flight either in the field or in the laboratory. Spontaneous claps (i.e. those not following other activity) became commoner at 33- 34°C, and also in hypoxic atmospheres. Additionally teneral adults, experiencing oxygen shortage, commonly made 3 types of movement not seen in more mature adults, but resembling larval respiratory responses. These were side-to-side shaking movements (often accompanied by a single wingelap), sustained wing opening by 20- 40° and periodic body raising (’press-ups’). — Measurements have shown that in C. splendens up to 1.4 pi air stroke-1 is displaced from the thorax by forced wing movements, indicating that about 14 pi g-l stroke I could be autoventilated during flight, a figure comparable to T. WEIS-FOGH’s (1967, J. exp. Biol. 47; 561-587) values for aeshnids. It is concluded that wingclapping may serve both respiratory and thermoregulatory functions, the latter by circulating air internally and externally. Wingclapping may be necessary in calopterygids because of their relatively large size and inefficient abdominal ventilatory pump.