Determination of wing length and diapause in water-striders (Gerris Fabr., Heteroptera)

Different wing morphs of Gerris lacustris (L.) have been crossed in different photoperiods and at high temperatures in laboratory. A new, tentative hypothesis is presented to explain both the laboratory experiments and the alary morphs found in different European populations of Gerris species. According to this hypothesis wing length is controlled by a photoperiodic switch, which is more or less adjusted by temperature. The hypothesis can be extended to account for the pronounced differences in alary lengths and morph ratios between different species. In G. lacustris and G. lateralis Fieb. a genetic switch produces two types which differ in their reaction with regard to the temperature switch. Imaginal diapause is the result of a shortening illumination rhythm during larval development.