The effect of sex ratio and group density on the mating success of two lines of Delia platura (Diptera: Anthomyiidae)

Abstract

Abstract The seedcorn maggot, Delia platura (Meigen) (Diptera: Anthomyiidae), is reported as a polyphagous pest species found in numerous crops, including onion, corn, crucifers, and soy. Two morphologically identical genetic lines of D. platura (H- and N-lines) with distinct distribution ranges were recently discovered. Although many biological traits have been described for D. platura, no study to date has been conducted on the life history strategies and reproductive behaviours of its two lines. Using laboratory-reared colonies, this project investigates the effect of group composition (sex ratio and density) on the mating success and preoviposition period of the two D. platura lines. We found a substantial increase in mating success with increasing proportion of males within mating groups for both lines, whereas we found group density had negligible effects. However, the H-line had a lower average mating probability across treatments compared to the N-line. The preoviposition period decreased as the ratio of males to female increased at low density only for the N-line, and the opposite trend was observed at high density for both lines. These results suggest differences between the mating systems of these two lines, thereby highlighting the need for further research into the factors that influence their respective mating systems.