Age structure and reproductive composition of summer Musca autumnalis (Diptera: Muscidae) populations estimated by pterin concentrations.

Pterins in face flies, Musca autumnalis DeGeer, were measured spectrofluorimetrically to estimate the chronological ages of adults in natural summer populations. The age distributions showed a systematic undersampling of young males. Exponential, Gompertz, and Weibull models were fitted to the age distributions. A 1-parameter exponential model suggested mean daily survival rates of 0.83 for female face flies, and a mean life expectation of 5.5 d. But the Weibull model best fit the age distributions, providing mean life expectations of 10.1 and 11 d for males and females, respectively. Ovarian dynamics were examined with respect to chronological age and delays were detected in vitellogenesis and oviposition. Face fly populations seemed to reproduce at less than the maximum rate allowed by prevailing temperatures, at which it was estimated that an average female would undergo 2.2 ovarian cycles and have a lifetime fecundity of 28.5 female progeny.