The Progress of Nymphal Development in Pest Grasshoppers (Acrididae) of Western Canada

Abstract

Each of the three grasshopper species, Camnula pellucida, Melanoplus bilituratus and M. bivittatus, spent approximately 13, 17, 19, 22 and 29% of total time in nymphal development in the successive five instars. These proportions appeared similar at each of the six rearing temperatures 75, 80, 85, 90, 95 and 100°F. The times required for total nymphal development at these temperatures were 53, 36, 28½, 23½, 18 and 17 days, respectively. It was estimated that, for the grasshoppers to complete nymphal development and attain sexual maturity in time to have a reasonably good chance of successful reproduction, their integrated temperature experience for 12-hour days should be not less than 95°F. Whereas the apparent mid-point of nymphal development in terms of morphogenesis is midway through the third instar in the typical five-instar grasshoppers, the midpoint of time spent at constant temperatures is near the end of the third instar. C. pellucida appears unable to complete nymphal development at a temperature as low as 75°F.; the Melanoplus species, however, can complete development at this temperature, but with reduced survival.