Evolution of arboreal tunnelling by larvae ofAenetus(Lepidoptera: Hepialidae)

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Abstract
Aspects of larval feeding and tunnelling were described for seven species of the wood-boring genus Aenetus. The species were studied in Australia, New Caledonia, and New Zealand. A sequential pattern of larval feeding involving transfer from a fungal based diet to callus tissue in live trees, previously known for A. virescens, was confirmed for A. cohici and inferred for A. dulcis and A. paradiseus. A specialised “transfer” morph linking the two feeding stages in A. virescens was also confirmed for A. cohici and two unidentified species. The wood-boring habit involved entry into the host above ground level and the construction of a tunnel which extends into and then down the stem. Tunnels were often located on the lower surface of leaning branches or stems. Tunnel entrances were open to the host surface, but overlain by a silk- /frass web. Bark and underlying tissue were removed from around the tunnel entrance and a callus growth resulted, which the larva consumed. The evolutionary history of arboreal tunnelling in the Hepialidae was investigated using biogeographic analysis of generic distribution. It is argued that evolution and variation in arboreal tunnelling resulted from specialised recombinations of generalised ancestral characters. It is suggested that the study of arboreal tunnelling can provide a source of useful characters for systematic analysis of phylogenetic relationships within Aenetus. The potential systematic value of tunnel characters is illustrated for A. virescens.