SOME EFFECTS OF TEMPERATURE ON DEVELOPMENT AND DIAPAUSE IN EGGS OF MELANOPLUS BIVITTATUS (SAY) (ORTHOPTERA: ACRIDIDAE)

Abstract

The normal hatching curve of postdiapause eggs of Melanoplus bivittatus (Say) at 25 °C. is described and compared with those at 10, 15, and 20 °C. The rate of postdiapause katatrepsic development was proportional to temperature; extrapolation showed 12 °C. to be the theoretical threshold of normal development for this stage. However, restricted postdiapause development or conditioning occurred at 5 °C. At 10 °C, and less extensively at 5 and 15 °C., partial development took place, resulting in deformed embryos.Diapause, which is most readily broken at 5 °C., may persist for more than 100 days at that temperature. It can also be eliminated at 25 °C., but much more slowly. Alternating-temperature experiments disclosed no marked differences in the ease of diapause-breaking at various embryonic ages. The suggestion is made that temperature alternations hinder diapause-breaking and morphogenesis.The threshold of development concept is briefly discussed with regard to some of the observations reported.