A 100-million-year old slim insectan predator with massive venom-injecting stylets - a new type of neuropteran larva from Burmese amber

Abstract

meta bola – including bees, flies, butterflies, beetles and many more – is incredibly successful by numerous mea sures, be it species richness, biomass, or numbers of individuals. Part of this success has been attributed to the niche differentiation between larvae and adults. Due to this, in most cases, adult holometabolans avoid exploitation competition with their own offspring. This has obviously led to highly specialised adults, but also to highly specialised larval forms. Caterpillars of butterflies (Lepidoptera) and sawflies (Hymenoptera) are highly efficient herbivores, transforming plant parts into insect biomass. Larvae of other groups have different ecological roles. The larval forms of neuropterans, lacewings, are highly specialised predators (with only few exceptions). Their mouthparts form two forward oriented (prognathous) venom-injecting stylets (e.g. Aspöck et al. 2001, 2012; Beutel et al. 2010); each mandible (upper jaw) forms a stylet with an enditic protrusion (generally interpreted as the lacinia) of the next posterior mouthpart (maxilla; lower jaw). Within the diverse subgroups of Neuroptera many different variations of this basic scheme have evolved. Many of these stylets are curved. In this way the piercing tips are facing towards each other. This arrangement is an almost ideal solution for the mechanical challenge that while piercing a prey a counteracting force is necessary; otherwise the piercing animal would simply push itself back from the prey. In counteracting mouthparts, the counteracting force is provided by the other mouthparts. This mechanical solution is not only realised in many neuropteran larvae, but also in the venom­injecting maxillipeds of most centipedes (see Haug et al. 2014 and references therein for a detailed discussion) as well as the venom­injecting chelicerae of labidognathan spiders. Among the neuropteran larvae with curved stylets also many variations occur. The larvae of green lacewings