Mating behavior of the cabbage beetle, Colaphellus bowringi (Coleoptera: Chrysomelidae)

Circadianmatingrhythms,matingfrequency,matingduration,andtheeffectof matingdurationonfecundityandfertilityinthecabbagebeetle,Colaphellusbowringiwere investigated in the laboratory. Mating occurred throughout the 24-h cycle but the majority ofcopulationsoccurredinthephotophasewithtwoapparentpeaks,oneat8:00andanother at 16:00. Mating frequency observations for 10 consecutive days indicated that pre-mating period of C. bowringi was about 4 days, and pairs mated an average of 5 times per day and an average of 40 times during the first 10 days. There was a negative correlation between mating frequency and mating duration during the consecutive mating. The mean duration ofthefirstcopulation(136.24 ±4.62min)wassignificantlylongerthanthoseofthesecond (57.87 ± 2.03 min), third (53.05 ± 2.05 min) and fourth copulation (30.86 ± 2.98 min). Fecundity showed a slight increase with increasing mating duration but no significant difference among treatments. However, fertility was significantly influenced by the mating duration in this species. Mating of 20-min duration did not produce viable eggs. The mean percentage of fertile eggs with completed mating duration (204.43 ± 18.96 min, 56.75% fertile eggs) was significantly higher than those with 60 min (39.55%) and 30 min (17.91%) mating duration, suggesting that the longer mating duration might be associated with transfer of more sperm that are used to increase the fertility of eggs.