COMPARISON OF AGE STRUCTURE OF 3 MELANOPLUS SPP (ORTHOPTERA, ACRIDIDAE) IN WINTER-WHEAT AND ADJACENT RANGELAND

Significant differences in age structure of grasshopper populations [M elanoplus sanguinipes (Fabricius), M. bivittatus (Say), and M. packard ii Scudder] occurred in winter wheat and adjacent rangeland. In 1988, age structure differences were associated with density shifts in winte r wheat between sample periods suggesting that older instars dispersed into the crop but younger instars remained in rangeland. In 1989 ther e was some partitioning of age classes between the two habitats, but n o pattern emerged as in 1988. In 1990, significantly more older instar s were collected in winter wheat than in rangeland. There were shifts in percentage density of the three grasshopper species in winter wheat but again no patterns emerged.