Suppression of Grasshoppers by Nemestrinid Parasites (Diptera)

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Abstract
This paper supplements an earlier (1952) report on parasitization of Metalor pardalinus (Sauss.) by Trichopsidea clausa (O.S.) in Montana, but deals chiefly with the effect of Neorhynchocephalus sackenii on a host population of Melanophis bilituratus (Walk.) in eastern Oregon in 1955–56. On a 200,000-acre area, a 99% reduction of an outbreak of bilituratus coincided with heavy parasitization by N. sackenii, when 70% of the hosts taken in net collections were found parasitized. Decline of the host population resulted from shortened life span and reduced egg production by parasitized individuals. In cage tests, parasitized M. bilituratus, M. bivittatus (Say), and M. femur-rubrum (DeG.) lived not more than half as long as unparasitized individuals, and their egg production was reduced by 93%, 49%, and 95%, respectively. Though M. bivittatus was found heavily parasitized in the field, apparently it is not a true host of N. sackenii as none of the fly larvae reached maturity in 180 specimens kept under observation. Parasitization of M. femur-rubrum was accomplished under laboratory conditions, by placing a sackenii larva on the abdomen of each host and watching it until penetration was complete.

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