Effect of reflex bleeding of a predatory ladybird beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), as a means of avoiding intraguild predation and its cost

Abstract

In aphidophagous ladybird beetle, larvae reflexively exude hemolymph, i.e. reflex bleeding, when disturbed. In the present study, to evaluate the effectiveness of hemolymph as a defense against intraguild predation and its bleeding cost, laboratory experiments were conducted using two species, Coccinella septempunctata brucki and Harmonia axyridis. In the first experiment, to evaluate the effect of H. axyridis hemolymph as a means of avoiding intraguild predation by C. septempunctata brucki, the incidence of cannibalism of C. septempunctata brucki eggs by fourth instars was determined in relation to the presence of H. axyridis hemolymph. In this experiment, 80% eggs of C. septempunctata brucki were cannibalized when no H. axyridis hemolymph was present; however, only 20% of eggs were cannibalized when H. axyridis hemolymph was present. In the second experiment, average adult body weight of H. axyridis at its emergence differed after individuals had experienced no versus daily reflex bleeding during the fourth instar. The body weight of adult H. axyridis averaged 32.8±1.3 mg (n=11) and 35.3±0.9 mg (n=19) for males and females, respectively, when they did not reflex bleed during the fourth instar; however, their body weight tended to be lower when they had reflex bled daily during the fourth instar.