Developmental polymorphism in the red-legged grasshopper, Melanoplus femurrubrum (DeGeer) (Orthoptera: Acrididae)

Instar number in Melanoplus femurrubrum (DeGeer) is variable. Virginia populations were found to be developmentally polymorphic, having from five to eight nymphal instars. Variation in instar number among populations, between years, and within seasons is due to variation in early season temperatures. A laboratory population had six to eight instars, with fewer instars occurring at lower rearing temperatures. Females went through more instars than males. Antennal segment number was correlated with instar number.