A trunk-nesting form of the processionary caterpillar Ochrogaster lunifer (Lepidoptera: Notodontidae) restricted to a single host species Corymbia tessellaris (Myrtaceae), with some comparisons to the ground-nesting form

Abstract

The Bag-shelter moth Ochrogaster lunifer (Lepidoptera: Notodontidae: Thaumetopoeinae) is an endemic species of medical and veterinary importance that occurs throughout Australia. The gregarious species is variable with four phylogenetic clades recently identified. One clade comprises trunk-nesters restricted to one host: the Moreton Bay Ash, Corymbia tessellaris (Myrtaceae). Here, we describe aspects of the biology and ecology of this distinctive nesting form dupped the ‘tree-hugger’ due to its flattish, thick silk nests that hug the trunk and larger branches. The form is univoltine; egg masses are laid in spring and the gregarious larvae develop through seven instars until the mature larvae stop feeding in autumn and later leave the nest (in a procession). The larvae over-winter in the ground as pre-pupae in a loose cocoon of silk. Pupation occurs in late winter and adults emerge in spring. Forty-six per cent of monitored egg masses succeeded in developing through the lifecycle. Tachinids were common parasites of older larvae. Tree-hugger nests provided some insulation against summer heat during the mornings, but the physical characteristics of the nests and tree trunks and the average southern orientation of the nests likely protect larvae against extreme heat. The tree-hugger form of O. lunifer appears morphologically similar to the more ubiquitous ground-nesting form, but there are differences in the colour of egg masses and adults, and in the behaviour and ecology of the larvae and adults. This information adds to the body of evidence supporting the definition of separate species within what is currently known as O. lunifer.