The relationship between population density, juvenile hormone, juvenile hormone esterase and phase variation in larvae of the migrant insect, Anticarsia gemmatalis Hübner

Juvenile hormone esterase activity in synchronous ultimate-stadium larvae varied with development time and density but larval weight was not associated with esterase activity. Topical application of epofenonane to crowded ultimate-stadium larvae resulted in juvenile hormone esterase activity levels that were similar to uncrowded larvae indicating that esterase activity is in part, a function of the juvenile hormone titre. Reducing the density at the ultimate stadium of Anticarsia gemmatalis resulted in pupal and adult weights, and larval durations that were intermediate between larvae reared crowded or uncrowded throughout development. Juvenile hormone I and the juvenoid epofenonane inhibited dark pigmentation of crowded larvae when applied before dark pigmentation occurred in the ultimate stadium. Application of epofenonane to crowded larvae increased the pupal weight and larval duration. These results suggest that the juvenile hormone titre of crowded A. gemmatalis larvae is lower than uncrowded larvae.