Some sawfly larvae survive predator-prey interactions with pentatomid Picromerus bidens.

Most Asopinae stinkbugs (Hemiptera: Pentatomidae) prey on other insects, including sawfly larvae (Hymenoptera: Symphyta). Sawfly larvae of the Argidae and Pergidae contain toxic peptides, but whether they are defended against stinkbugs remains poorly studied. A literature survey indicates that no publication is devoted to laboratory tests specifically using these sawflies against stinkbugs. Here, laboratory bioassays were made with the stinkbug Picromerus bidens and four sawfly species at last larval instars: Arge ochropus (Argidae), Arge pagana (also tested at medium instars), Lophyrotoma zonalis (Pergidae), and Allantus rufocinctus (Tenthredinidae). Following 24 h of possible predator-prey interactions, no larvae of A. rufocinctus survived, whereas most or all larvae of the other sawfly species did survive and were still alive 48 h later. When feeding on an argid or pergid larva, the feeding periods lasted on average 6-20 s only, some bugs removing their rostrum and abruptly backing away. Full-grown larvae of A. pagana were attacked less than younger ones. It is likely that the tested Argidae and Pergidae are well defended against P. bidens by potent, internal antifeedants, while defensive body movements combined with a large body size play a secondary role.