Time measurement in insect photoperiodism: The role of photophase duration and light intensity

The initial stages of diapause induction - as summer gives way to autumn involve a process time measurement in which the duration daylength (or nightlength) is determined by photoperiodic 'clock' based upon circadian system. In many insects so far examined, photophase sufficient and illuminance resets oscillator constant phase equivalent beginning 'subjective night' (Circadian time, CT 12 h) whereupon it proceeds measure nightlength clock external coincidence type. A possible exception may be found linden bug, Pyrrhocoris apterus, laboratory studies using relatively low light intensity suggests that measured rather than night. Earlier responses (pupal induction) flesh fly Sarcophaga argyrostoma, however, showed 'weak' or short pulses giving rise Type 1 response curves could converted increasing 0 set oscillation subjective night (CT begin Based these data therefore suggested P. apterus might also if bugs were exposed photophases higher irradiance simulating daytime exposure experienced diurnally active their natural environment.