Systematics and biology of the iconic Australian scribbly gum moths Ogmograptis Meyrick (Lepidoptera : Bucculatricidae) and their unique insect–plant interaction

Abstract

Many smooth-barked Eucalyptus spp.in south-eastern Australia bear distinctive scribbles caused by the larva of some Ogmograptis spp. However, although these scribbles are conspicuous, the systematics and biology of the genus is poorly known. This has been addressed through detailed field and laboratory studies of the biology of three species (O. racemosa Horak, sp. nov., O. fraxinoides Horak, sp. nov., O. scribula Meyrick) in conjunction with a comprehensive taxonomic revision supported by a molecular phylogeny utilising the mitochondrial Cox1 and nuclear 18S genes. In brief, eggs are laid in bark depressions and the first-instar larvae bore into the bark to the level where the future cork cambium forms (the phellogen). Early-instar larvae bore wide, arcing tracks in this layer before forming a tighter zig-zag-shaped pattern. The second-last instar turns and bores either closely parallel to the initial mine or doubles its width, along the zig-zag-shaped mine. The final instar possesses legs and a spinneret (unlike the earlier instars) and feeds exclusively on callus tissue that forms within the zig-zag-shaped mine formed by the previous instar, before emerging from the bark to pupate at the base of the tree. The scars of mines then become visible scribbles following the shedding of the outer bark. Sequence data confirm the placement of Ogmograptis within the Bucculatricidae, suggest that the larvae responsible for the ‘ghost scribbles’ (raised scars found on smooth-barked eucalypts) are members of the related genus Tritymba Meyrick, and support the morphology-based species groups proposed for Ogmograptis. The formerly monotypic genus Ogmograptis Meyrick is revised and divided into three species groups. Eleven new species are described: Ogmograptis fraxinoides Horak, sp. nov., Ogmograptis racemosa Horak, sp. nov., and Ogmograptis pilularis Horak, sp. nov., forming the scribula group with Ogmograptis scribula Meyrick; Ogmograptis maxdayi Horak, sp. nov., Ogmograptis barloworum Horak, sp. nov., Ogmograptis paucidentatus Horak, sp. nov., Ogmograptis rodens Horak, sp. nov., Ogmograptis bignathifer Horak, sp. nov., and Ogmograptis inornatus Horak, sp. nov., as the maxdayi group; Ogmograptis bipunctatus Horak, sp. nov., Ogmograptis pulcher Horak, sp. nov., Ogmograptis triradiata (Turner), comb. nov., and Ogmograptis centrospila (Turner), comb. nov., as the triradiata group. Ogmograptis notosema (Meyrick) cannot be assigned to a species group as the holotype has not been located. Three unique synapomorphies, all derived from immatures, redefine the family Bucculatricidae, uniting Ogmograptis, Tritymba (both Australian) and Leucoedemia Scoble & Scholtz (African) with Bucculatrix Zeller, which is the sister group of the Southern Hemisphere genera. The systematic history of Ogmograptis and the Bucculatricidae is discussed.