PHOTOPERIODIC REGULATION OF MATING-BEHAVIOR IN THE LINDEN BUG, PYRRHOCORIS-APTERUS, IS MEDIATED BY A BRAIN INHIBITORY FACTOR

Active inhibition of mating behaviour in a male insect is reported her e for the first time. In Pyrrhocoris apterus L. (Heteroptera), the mos t important inhibitory pathway runs from the pars intercerebralis (PI) of the brain and does not pass through the corpora allata. The inhibi tory activity of the PI is promoted by short day conditions and suppre ssed by long days. As the effect of photoperiod is delayed, transfer p rocedures enabled us to record daily rhythms in mating behaviour durin g short days. While the extirpation of the PI results in a discrete ph ase shift of the long day rhythm, there is a much less significant pha se shift after this operation during short days. Thus the PI has been shown to mediate the effect of photoperiod on bath the inhibition and the rhythm of mating behaviour.