TEMPERATURE EFFECT ON POSTDIAPAUSE DEVELOPMENT AND SURVIVAL OF EMBRYOS OF 3 SPECIES OF MELANOPLUS (ORTHOPTERA, ACRIDIDAE)

Postdiapause development and survival of embryos to hatch were studied at 10 constant temperatures (12, 15, 18, 24, 27, 30, 33, 36, 39, and 42-degrees-C) for three species of North American grasshoppers: Melano plus sanguinipes (F.), M. bivittatus (Say), and M. differentialis (Tho mas). M. sanguinipes and M. bivittatus had similar development curves (rate versus temperature) with developmental thresholds of 10.4 and 9. 8-degrees-C, respectively. M. differentialis had a slower development curve, but the developmental threshold was 8.8-degrees-C. Even though M. differentialis had a lower developmental threshold, mean hatch days , the time to the first day of hatch, and the respective thermal units were nearly double those of M. sanguinipes or M. bivittatus. Percenta ge of hatch was greatest at 26.8-degrees-C for M. sanguinipes, at 24-d egrees-C for M. bivittatus, and at 26.3-degrees-C for M. differentiali s; thermal death points were reached at 43, 42, and 42.3-degrees-C, re spectively.