Assessment of toxic and developmental impacts of methoprene on the grey flesh fly Parasarcophaga argyrostoma (Diptera: Sarcophagidae)

Abstract

Beside its role in human cutaneous wounds and eye myiasis, the grey flesh fly Parasarcophaga argyrostoma (Robineau-Desvoidy) (Diptera: Sarcophagidae) is known as parasitoid of various animals. Objective of the current study was the evaluation of methoprene impacts on survival, development and metamorphosis of this fly. Five doses (10.0, 5.0, 1.0, 0.1 and 0.01µg/larva) were prepared and topically applied onto the early last (3rd) instar larvae and prepupae.Thirty replicates (one larva/replicate) of healthy larvae or prepupae were topically treated, individually using Hamilton microapplicator (NHN 737). Similar number of replicates of larvae and prepupae had been topically treated with 1µ acetone only as controls.The most important results can be summarized as follows. Methoprene exhibited larvicidal, pupicidal and adulticidal activities. LD50 values were found 0.155 and 0.258 µg/insect after treatment of larvae and prepupae, respectively. The maximal body weight of treated larvae was remarkably reduced. The duration of treated larvae was prolonged. The growth coefficient of treated larvae was depressed. The pupal duration was considerably prolonged. Only at the higher two doses, some larval-pupal intermediates had been observed. After treatment of prepupae, only with the lower two doses, a state of ‘permanent prepupae’ was recorded. The pupation rate was slightly regressed after treatment of prepupae, only with the lower two doses. The adult emergence was completely blocked after topical treatment of either larvae or prepupae with the highest dose of methoprene. At other dose levels, the adult eclosion was partially blocked. Different percentages of deformed pupaeand adults were recorded.