COLORS, COLOR-CHANGE, COLOR PATTERNS AND (CUTICULAR WINDOWS AS LIGHT TRAPS - THEIR THERMOREGULATORIC AND ECOLOGICAL SIGNIFICANCE IN SOME AESHNA SPECIES (ODONATA, AESHNIDAE)

Male and female Aeshna caerulea, A. cyanea, A. juncea and A. mixta wer e illuminated with a halogen and a infrared lamp, and intraabdominal t emperatures (T-abd), threshold temperatures of certain behaviours duri ng warm-up (beginning eye-cleaning, wing-whirring and take off) and wa rm-up times were taken. Especially the two colour phases in male A. ca erulea, which are able to perform physiological colour change, have be en taken into account. Depending on colours and colour patterns T-abd varied in species and conspecific sexes. T-abd was only Little, if at all, affected by body mass. Abdominal heat gain was high in dull colou red abdominal segments (in females and male A. caerulea in dark colour phase) due to high light absorption, and low under Tyndall-blue spots (e. g. male A. caerulea in blue colour phase) due to high light refle ction. The Tyndall-blue seems to effect as 'overheating-protector'. It is supposed that different diurnal activity patterns in females and c onspecific males are mainly caused by body colours and colour patterns . In aeshnids pigments are situated in the epidermis and are visible o nly through translucent cuticular areas. Together with epidermal pigme nts, these 'cuticular windows' are conceived as light-traps maximizing the efficiency of incident light and limiting abdominal heat gain (he at protection) to certain spots only, e.g. to support the work of abdo minal organs.