Laboratory studies on the life-history of the grasshopperHumbe tenuicornisSchaum (Orthoptera: Acrididae: Oedipodinae) in relation to density and phase

Abstract

The biology of the African grasshopper Humbe tenuicornis Schaum was studied under controlled laboratory conditions. The ground colour of the first instar hoppers from the crowded stock was a uniform brown, but those from the isolated stock were of a slightly lighter brown. After the first instar the nymphs at both densities produced a range of colours changing from instar to instar. The majority of the hoppers of the isolated stock in the last instar were of a light brown colour and those of the crowded stock were of black or almost black colour with a lighter coloured abdomen. No green individuals were produced in either rearing density. Both isolated and crowded hoppers had five nymphal instars. There was no significant difference between the length of nymphal life of the isolated and crowded males, but at both densities female development was significantly slower. The adult morphometric analysis has shown that the isolated insects were significantly bigger in certain characters than the crowded ones. There was no significant difference in the rate of sexual maturation of the two rearing densities. The crowded females were much less fecund and fertile than the isolated ones, which lived longer. The hatchlings from the crowded stock were very highly significantly heavier than those from the isolated stock. No diapause was detected at any stage of the life-cycle and it was possible to obtain five generations a year in the laboratory.