Habitat requirements of Tetanocera elata (Diptera: Sciomyzidae): case study of a dry meadow in western Ireland

Terrestrial slugs are pervasive pests of agriculture throughout temperate regions and have the potential to disrupt the germination of seedlings, cause damage to fruiting bodies of crops, and vector plant pathogens. Tetanocera elata Fabricius (Diptera: Sciomyzidae), a widely distributed Palaearctic species, is an obligate mesoparasitoid and predator of pestiferous slugs including Deroceras reticulatum Müller (Stylommatophora: Agriolimacidae). It has the potential to be developed as a native natural enemy in a conservation biological control programme as an alternative to chemical molluscicides. To better understand the ecological requirements of this species, a detailed observational study was conducted at a site in the west of Ireland possessing naturally occurring T. elata populations. Comparison of local patches where T. elata were recovered revealed no association with plant community composition. Taller dead vegetation was associated with T. elata presence throughout the site. Within the area of greatest T. elata aggregation, there was a significantly greater percentage cover of dead vegetation where T. elata occurred. Abundance of T. elata was also significantly correlated to hedgerow proximity. Results of this study are directly applicable for the design of a conservation biological control programme, which effectively satisfies the principal habitat requirements of T. elata populations

Estimating total losses from parasitoids for a field population of a continuously breeding insect, cassava mealybug, Phenacoccus herreni, (Homoptera: Pseudococcidae) in Colombia, S.A.

A Phenaccocus herreni Cox & Williams population studied in Colombia, S.A., across a complete cassava crop cycle did not exceed 81 mealybugs/plant. P. herreni densities in Colombia were highest in the dry season, as were levels of parasitism by the encyrtids Acerophagus coccois Smith and Epidinocarsis diversicornis (Howard). Mealybug densities declined sharply during the dry season prior to the onset of rains. Stage survival among female mealybug nymphs was lowest in the third instar. Nine percent of all female first instar mealybugs survived to enter the adult stage. The combined action of the parasitoid species present caused 54.9% mortality to the host population as estimated by a new analytical method (Bellows et al. 1989)