Inhibitory effects of methoprene on emergence of stable fly

Abstract

The emergence inhibitory effect of a juvenile hormone analogue, methoprene, was evaluated for the larvae of the stable fly, Stomoxys calcitrans (L.), by the fly medium method and dipping method in the labaratory. In both methods no larva was apparently effected in pupation, but many pupae were inhibited from emergence. By the fly medium method most emergences were inhibited by the concentrations above three ppm, except a single fly with three-ppm treatment. Among the emerging adults treated with lower concentrations, malformed flies with reduced wings and tiny body size appeared frequently. The malformation ratio increased with higher concentrations. By dissecting dead puparia inhibited from emergence under a binocular microscope, the state of metamorphosis inside was morphologically examined. Many remained in larval form in control. On the contrary, most of them in treatment finished adult morphogenesis and reached the pre-emergence state, completing cuticularization and pigmentation and having apparently normal bodies. A number of malformed adult forms with the incomplete abdominal segmentation inside puparia appeared in higher concentrations by the fly medium method. Therefore, it was hypothesized that methoprene might act inhibitorily on the emergence mechanism and metamorphosis in the pupal stage of stable flies.