Quality of two aphid species (Rhopalosiphum padiandSitobion avenae) as food for the generalist predatorTachyporus hypnorum(Col., Staphylinidae)

The quality of two aphid species (Rhopalosiphum padiandSitobion avenae) as food for the staphylinid generalist predatorTachyporus hypnorumwas investigated. Fruit flies (Drosophila melanogaster) were used as prey for comparison.T. hypnorumhas been reported to prey on aphids, to consume large quantities and to show a high preference for aphids. This study showed that compared with fruit flies aphids are not high‐quality prey for neither adult females nor larvae ofT. hypnorum. Larvae were less able to utilize aphids than adult females. Reproduction was affected by both aphid species; a diet ofS. avenaereduced fecundity, and a diet ofR. padireduced egg hatching success and prolonged the time spent in the egg stage compared with a fruit fly diet. For theT. hypnorumlarvae pure diets of bothS. avenaeandR. padiresulted in high larval mortality. Overall ranking of the three prey types based on several fitness parameters differed between larvae and adults. The adult fitness parameters gave rather conflicting rankings of all three prey types though the two aphid species were of approximately the same overall value, whereas the larval fitness parameters gave identical rankings:D. melanogaster > S. avenae > R. padi. In the larval stage survival was greatly reduced by both aphid diets, while this was not the case for the adult females.