The effects of gregarine parasites on longevity, weight loss, fecundity and developmental time in the field crickets Gryllus veletis and G.pennsylvanicus

ABSTRACT. 1. Gregarines, debilitating gut parasites, significantly reduced longevity and increased weight loss in the field cricket Gryllus pennsylvanicus Burmeiser when adults were kept on suboptimal diets, but in G.pennsylvanicus and G.veletis (Alexander and Bigelow) fed ad libitum, weight change, longevity, and fecundity were not significantly different in infected and control individuals. 2. Adults harbouring gregarines at eclosion took significantly longer to develop from the second and third instars than did uninfected adults. 3. Longevity of nymphs kept in the laboratory without food was decreased in infected individuals compared with uninfected ones, but not significantly so. 4. The evolutionary and ecological implications of nonlethal parasites are discussed.