Rhythmic activity of adult carrot fly, Psila rosae

ABSTRACT. In a laboratory study of adult carrot fly activity, observations were made on caged populations and on individuals isolated in actographs. In cages in LD 12:12, feeding, oviposition, flight and possibly mating were all rhythmic. Peak feeding occurred within 1 h from lights-on and peak oviposition and flight 10–12 h later. Mating frequency increased slightly in the latter half of the light phase. In actographs in LD 12:12, peak activity also occurred 10–12 h after lights-on. Activity increased with age up to at least 5 days old, independently of the effects of starvation, and by day 5 males were approximately 3 times and females 8 times more active than on the day of emergence. Overall, males were approximately 1.4 times more active than females. Females isolated in actographs for 4 days in continuous dim light showed peaks of activity at intervals of approximately 22.5 h, and activity therefore appears to be a true circadian rhythm. In continuous bright light the activity of females became arrhythmic.