Anti-predator defence mechanisms in sawfly larvae of Arge (Hymenoptera, Argidae)

Abstract

Larvae of the sawfly Arge (Hymenoptera, Argidae) are exposed to predators such as ants. Their defence mechanisms, which have been almost unstudied, were investigated by behavioural observations coupled to a morphological approach and by testing the bioactivity of several body parts. Arge larvae raised their abdomen when contacted by Myrmica rubra workers. The ants rarely bit a larva and generally retreated immediately, sometimes without contacting it. Most of those few ants that bit a larva then showed an uncoordinated walk. Crude hemolymph from a common species, A. pagana, was a feeding deterrent towards ants. Hemolymph extracts remained active up to a concentration of 0.8 µg DW extract per microlitre solution, and were more active than integument and gut extracts. We also observed ants paralysed by extracts, especially from the gut. It is likely that this toxicity is due to a polypeptide, lophyrotomin, which is known to occur in A. pullata. Six or seven non-eversible ventro-abdominal glands occurred in all species studied (A. fuscipes, A. nigripes, A. ochropus, A. pagana, A. pullata, A. ustulata). These glands contain volatiles. We consider both types of chemicals to be important in defence, and we propose that the paralysing effect is a common feature among Arge species.

Arge xanthogaster(Hymenoptera: Argidae): A New Threat to Rose Plants in Meghalaya, India

“…In addition to this, a slight disturbance to A. xanthogaster larvae results in them curling their posterior body (in a snake-like manner), which may reinforce the effectiveness of the pubescence by producing a 'hedgehog effect'. Similar behaviors have been reported in A. pagana, and they are believed to be anti-predator defense activities (Petre et al 2007).…”

Toxic Peptides Occur Frequently in Pergid and Argid Sawfly Larvae

“…Once disturbed, they discharge a viscous oral fluid [39], [40], perhaps as an alternative defensive strategy. In laboratory bioassays, extracts from several isolated body parts of A. pagana and A. pullata proved to be effective as feeding deterrents against ants, and the extracts also rapidly paralyzed feeding ants; both of these bioactivities are ascribed to the action of peptides [32]. The taming of aggressive behavior by ants has been documented also for oligopeptides recently isolated from frogs [6].…”

“…However, we started our study from the hypothesis that the toxins would be found also in related but non-pullulating sawfly species. Experiments with extracts from larvae of Arge pagana , a species common on roses in Europe, and from A. pullata , that were tested on ants ( Myrmica rubra L., Formicidae) had caused the latter to show paralyzing effects [32]. These bioassay results indicated that A. pagana contains the toxic peptides just like A. pullata .…”

Haemolymph defence of an invasive herbivore: its breadth of effectiveness against predators

“…caespitum , a message was somehow conveyed to the remaining workers (either by the attacking ant, or by volatile infochemicals within the haemolymph), and few additional attempts were made to attack the D. v. virgifera larva. Because of their incredible effects on their environments (Hölldobler and Wilson 1990; Beattie and Hughes 2002), ants are often the target of haemolymph defences in insects (Boevé and Schaffner 2003; Petre et al. 2007), but laboratory results are seldom reinforced under field situations.…”