Rearing and biology of the decapitating fly Pseudacteon bifidus (Diptera: Phoridae): a parasitoid of tropical fire ants
Keywords:
Solenopsis geminata, sex ratios, development rates, host preferences, biological controlAbstract
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.
Resumen
La mosca decapitadora Pseudacteon bifidus Brown y Morrison (Diptera: Phoridae) es un parasitoide de la hormiga de fuego tropical, Solenopsis geminata (F.) (Hymenoptera: Formicidae). Esta mosca es de interés como un agente potencial de biocontrol autosostenible, ya que la hormiga de fuego tropical es una plaga invasora en zonas tropicales a nivel mundial, especialmente en las islas del Pacífico. El objetivo de este estudio fue desarrollar métodos para criar masivamente P. bifidus y estudiar aspectos relacionados con su biología. Las moscas utilizadas en este estudio se recolectaron cerca del Río Nueces al norte de Catarina, Texas, USA. Encontramos que P. bifidus parasita las trabajadoras menores con un ancho de cabeza promedio de 0,71 ± 0,10 mm (rango: 0,59–1,15). La proporción sexual de los adultos fue moderadamente sesgada hacia los machos (58:42%), con los machos emergiendo con una mayor probabilidad de los hospederos más pequeños y las hembras de los más grandes. El tiempo promedio generacional fue de 30 d a 27,6 °C. El tiempo de desarrollo larval promedio fue de 14 d a 27,6 °C, pero el patrón de desarrollo estaba muy sesgado con una moda de 11 d y alrededor del 15% de los individuos con una asimetría positiva de por lo menos 41 d. Los machos emergieron de las pupas más rápido que las hembras (0,8 d, 23,5 °C). A diferencia de otras especies de Pseudacteon, las hembras adultas se encuentranno estaban listas para ovipositar entre las 8 y 24 h después de emerger. Se pudieron producir 9.500 ± 2.800 mosquitas por generación modificando principalmente procedimientos de crianza preexistentes (1) proveyendo a los adultos acceso a agua y agua azucarada para que pudieran vivir más tiempo, (2) extendiendo el acceso a los hospederos por 1 para 2 días adicionales y (3) evitando la reutilización de colonias hospederas con tasas bajas de parasitismo. El costo de la mano de obra disminuyó al producir generaciones discretas y al usar una caja de ataque con la temperatura, humedad, iluminación y controles mecánicos automatizados que permitieron a las mosquitas emerger, aparearse y parasitar sus hospederos sin la necesidad de una manipulación constante. El éxito de estos esfuerzos para criar P. bifidus proporcionaron una base para estudios posteriors de especificidad y aceptabilidad del hospedero.
Supplementary material for this article in Florida Entomologist 101(2) (June 2018) is online at http://purl.fcla.edu/fcla/entomologist/browse
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