Biology and performance on different diets of an omnivorous insect predator, Psallus haematodes (Heteroptera: Miridae)

Omnivorous mirids (Heteroptera: Miridae) seem to be important biological control agents of willow leaf beetles. Here we describe the biology, the performance and survival on different diets of a mirid recently discovered to be relatively common in willow plantations, Psallus haematodes. Unlike some other mirids on willows, P. haematodes was found to feed only on leaf beetle (Phratora vulgatissima) eggs and not on larvae. In a series of greenhouse experiments we found also that the feeding rate increased gradually to reach its maximum in the last instar and adult stage, i.e. 1.9 eggs per day. Mirids provided with leaf beetle eggs developed faster (24±0.7 vs. 29±0.5 days), survived better (55 vs. 30%) and lived longer (10.1±1.1 vs. 5.7±1.2 days) than mirids only provided with willow shoots. Females provided with eggs also attained a higher weight than females without eggs (709±79 vs. 307±85 µg). Mirids provided with eggs, attained a lower final weight on detached shoots than on growing plants; males (453±28 vs. 602±41 µg) and females (709±79 vs. 898±30 µg). The fact that P. haematodes occurs later in the season than a predatory mirid (Orthotylus marginalis) known to play a key role in the biological control of leaf beetles makes it likely that these two mirids may act complementarily in biological control, despite many similarities in biology