Biology of autogenous horse flies native to coastal California: Apatolestes actites (Diptera: Tabanidae)

The immature stages of Apatolestes actites Philip & Steffan at a sandy ocean beach in California inhabited the supralittoral zone to depths of 8-36 cm in relatively saline soil that was acidic for at least 6 months a year. Adults flew from early June to mid-July. They emerged between 0751 and 1258 h, dispersed to the littoral and lower supralittoral zones, where they basked for up to 3 h, and then disappeared. Only gravid females returned to the beach area, where parous flies apparently remained after ovipositing. The life-span of confined newly emerged adults averaged 5.0 days for males and 9.3 days for females. Females developed their 1st batch of eggs autogenously in 6 days at 25°C and 67% RH; 4 wild-caught flies had also produced or were in the course of developing a 2nd batch of eggs autogenously. Fecundity averaged 322 eggs in the 1st gonotrophic cycle and 43 in the 2nd. Eggs hatched in 6-8 days, and the mean viability of 3 masses was 69%. Females laid their eggs in amphipod or isopod burrows, and rarely in driftwood. The mandibular and maxillary stylets of females were much reduced and presumably unable to pierce the skin of vertebrates. The barn swallow (Hirundo rustica) and the song sparrow (Melospiza melodia) preyed on the adult flies.