Rearing and Biology of the Decapitating FlyPseudacteon bifidus(Diptera: Phoridae): A Parasitoid of Tropical Fire Ants

Abstract

The small decapitating fly, Pseudacteon bifidus Brown and Morrison (Diptera: Phoridae), is a parasitoid of the tropical fire ant, Solenopsis geminata (F.) (Hymenoptera: Formicidae). This fly is of interest as a potential self-sustaining biocontrol agent because tropical fire ants are invasive pests throughout the world's tropics, especially on islands of the Pacific. The objective of this study was to develop methods for mass rearing P. bifidus and to study related aspects of its biology. The flies used in this study were collected near the Nueces River north of Catarina, Texas, USA. We found that P. bifidus parasitizes minor workers with an average head width of 0.71 ± 0.10 mm (0.59–1.15, range). The sex ratio of adult flies was moderately skewed to males (58:42%), with males slightly more likely to emerge from the smallest hosts and females from the largest ones. The average generation time was 30 d at 27.6 °C. Average larval development time was 14 d at 27.6 °C, but the pattern was highly skewed with a mode of 11 d and about 15% of individuals in a long tail of slow developing larvae, which extended out to at least 41 d. Male pupae emerged faster than female pupae (0.8 d, 23.5 °C). Unlike other Pseudacteon species, adult females were not ready to oviposit until 8 to 24 h after eclosure. We were able to rear 9,500 ± 2,800 flies per generation primarily by modifying preexisting rearing procedures (1) to provide adults access to water and sugar water so they could live longer, (2) by extending access to hosts for 1 to 2 extra d, and (3) by avoiding reuse of host colonies with poor rates of parasitism. Labor costs were decreased by rearing in discrete generations and the use of an attack box with automatic temperature, humidity, lighting, and mechanical controls that allowed flies to emerge, mate, and parasitize hosts without the need for constant management. The success of these rearing efforts provided a foundation for subsequent studies of P. bifidus host specificity and host suitability.