Influence of Feeding Treatment, Host Density, Temperature, and Cool Storage on Attack Rates ofTachinaephagus zealandicus(Hymenoptera: Encyrtidae)

Abstract

Tachinaephagus zealandicus Ashmead is a gregarious endoparasitoid that attacks third instars of muscoid flies, including house flies, Musca domestica L. A colony of this parasitoid was established from samples collected from a poultry farm in Santa Cruz da Conceição, São Paulo, Brazil. The objective of this study was to evaluate the influence of feeding treatment, host density and temperature on attack rates on T. zealandicus. Parasitoids that were given honey as adults attacked two to three times as many house fly larvae (25 host attacks/female/d) as parasitoids that were given only water or nothing. Host attacks and progeny production by T. zealandicus on house fly and Chrysomyia putoria increased over the range of host:parasitoid ratios tested, reaching a maximum of 21–22 hosts killed and 13 progeny produced/female/d at the highest host density of 32 larvae/female. Host attacks were higher at 22°C than at the other temperatures studied (20–29°C), but differences in attack rates were small over the range of 20–27°C (10–13 host attacks/female). Comparatively few hosts (6.3) were attacked at 29°C. Higher rates of progeny production also were observed among parasitoids tested at lower temperatures (9–11 progeny produced/female at 20–22°C) than at 29°C (1.8 progeny/female). Females of T. zealandicus that were stored at 15°C after emergence had highest rates of host attacks (58–62 hosts killed per group of five female parasitoids) and progeny production (174–261 progeny) after 6–12 d of storage at this temperature; relatively few hosts were attacked or parasitized (6–9 host attacks and progeny/group) after 0 or 1 d at 15°C.