The hypertrophied hindwings of Palmipenna aeoleoptera Picker, 1987 (Neuroptera: Nemopteridae) reduce attack by robber flies by increasing apparent body size

Abstract

Two possible anti-predator roles of the hypertrophied hindwings of the neuropteran, Palmipenna aeoleoptera were examined: that of decoys in redirecting robber fly attacks to less vulnerable parts of the body, and that of the contribution of these hindwings to apparent larger size. Eight species of robber fly, predominantly Neolophonotus species, coexisted with P. aeoleoptera at the study site in Biedouw valley, Namaqualand. A selectivity index showed that P. aeoleoptera was preferentially taken as prey. The hindwings of P. aeoleoptera apparently did not redirect robber fly attacks, as the majority of these took place on the body rather than on the hindwings. Live P. aeoleoptera with intact or amputated hindwings were used as lures in tether trials to determine whether the hindwings influenced attack by robber flies. A greater proportion of the robber flies (mainly N. expandocolis) preferentially attacked the lure with amputated hindwings, while those attacking the lure with intact hindwings ( N. abuntius and N. bimaculatus) were larger. Thus the hindwings of P. aeoleoptera would appear to deter attack by the more common, smaller robber flies by providing an illusion of greater size.