Estimates of female lifetime fecundity and changes in the number and types of sperm stored with age and time since mating in the monandrous swallowtail butterfly, Battus philenor (Lepidoptera: Papilionidae) in the Arizona desert

The role of apyrene sperm in monandrous species after sperm migration to the spermatheca has not been studied, though in polyandrous species these sperm reduce re-mating receptivity. We studied the relationship between apyrene sperm numbers and age, mating history, and fecundity in females of the monandrous pipevine swallowtail butterfly, Battus philenor (L.) that were collected in the desert of central Arizona. The number of spermatophores in the bursa copulatrix and the eggs in the ovaries were counted and their relationship to female age (as indicated by wing wear) was examined. The mean number of spermatophores in the oldest females was 1.4, confirming that this species is monandrous. Average female fecundity was estimated at 430 from counts of eggs in the ovaries. Recently mated females stored many more eupyrene sperm in the spermatheca than the number of eggs in the ovaries. Apyrene sperm were also found in the spermatheca of the females with a long period elapsed after the mating, as indicated by a collapsed spermatophore. The potential role of apyrene sperm and the effect of body size on the fecundity in monandrous species is mentioned.