Polymorphic development in relation to the life history of Melanoplus femurrubrum (Orthoptera: Acrididae)

The effects of polymorphic development on the life history of the redlegged grasshopper, Melanoplus femurrubrum (DeGeer), were investigated. In a population reared from field-collected eggs, the developmental threshold for six- and seven-instar groups was the same (17.1 degree C). Most mortality occurred in the first stadium. Developmental times of males and females in the same instar group were not different. At 26.5, 30, 35, and 38 degree C, seven-instar grasshoppers took 18.8, 11.1, 5,4, and 5.5 d longer to develop, respectively, than did six-instar grasshoppers. Within either instar group, females were larger than males, and within either sex, seven-instar individuals were larger than six-instar individuals. Females in field cages that became adults later in the season lived a shorter time and laid fewer egg pods because of the shortness of the remaining season.