Note on Dispersal of Radio-active Grasshoppers

Extract

Riegert et al. (1954) showed that nymphs and adults of Carnula pellucida (Scudd.) and Melanoplus mexicanus (Sauss.) released on bare, cultivated fields, dispersed up to 240 yards during six days. They showed no ability to orient themselves and move toward a food supply. Sixty per cent of M. mexicanus were within 50 yards of the release point after seven days. Experiments conducted from the Belleville laboratory in 1952 and 1953 showed that M. mexicanus dispersed less widely than this when released in a field population of grasshoppers, mostly M. mexicanus, where there was adequate food. This investigation was of special interest to the junior author (R. W. Smith), who was interested in relating the field distribution of adult parasites (as shown by the occurrence of immature parasites in captured grasshoppers) to various environmental factors. The validity of using such data for this purpose would depend upon the movement of the host from the time of parasitization to the time of capture. The following are details of the investigation.