Genetic Control of Albinism and the Role of Juvenile Hormone in Pigmentation in Locusta migratoria (Orthoptera, Acrididae)

Reciprocal crosses between an albino and normal strains of L. migratoria and backcrosses were conducted to determine the genetic control of the albino trait. The results indicate that this trait is recessive to the normal pigmented trait and controlled by a single Mendelian unit. When albino and normal young 4th instars were topically treated with different doses of methoprene or pyriproxyfen, some developed a green color on the body by the 3rd day after ecdysis to the 5th instar. Methoprene caused a few albinos to turn greenish, but it had no effect on normal hoppers even at the highest dose (50μg/insect) used. Such a difference was not observed for pyriproxyfen which was much more effective in inducing the green pigment in hoppers. To examine the role of juvenile hormone and the possible involvement of the corpora cardiaca in the induction of yellowing, which normally occurs only in crowded male adults, different doses of methoprene were applied on 3-day-old-normal adult males, albino males, and albino males which had been implanted at the beginning of the last hopper instar with a pair of corpora cardiaca from 2-3 week-old normal males. Examination of the body color 20 and 40 days after treatment revealed that methoprene accelerated the induction of yellowing dose-dependently in normal males but not in albino ones. However, in albinos implanted with normal corpora cardiaca, yellowing occurred as fast as in normal individuals, indicating that some factor in the corpora cardiaca might be involved in controlling the induction of yellowing.