RESPONSES OF MELANOPLUS-SANGUINIPES AND M-DIFFERENTIALIS (ORTHOPTERA, ACRIDIDAE) TO FENOXYCARB

Nymphs and adults of the grasshopper Melanoplus sanguinipes (F.) and nymphs of M. differentialis (Thomas) were treated with the juvenile hormone analog fenoxycarb by topical application or by ingestion of bait. Nymphal mortality was variable, but both species were significantly affected by topical treatment. Neither species succumbed to bait treatment. Both methods of application produced significant effects on nymphal development time, but the nature of the response varied with time of application, and the degree of the response (< 20%) was of questionable biological importance. Fenoxycarb induced morphological deformities, principally wing twisting. Temporary induction of green coloration was also noted, especially in M. differentialis. The most important effect of fenoxycarb application was disruption of reproduction; topical application of M. sanguinipes nymphs at 100-mu-g/insect resulted in complete elimination of egg pod production, and ingestion of 1 and 5% fenoxycarb on bran bait reduced oviposition. M. sanguinipes treated as adults were unaffected by fenoxycarb administered by topical application of up to 100-mu-g/insect or ingestion of 10% bran bait.