Humble beginnings of the Australian giant wood moth (Endoxyla cinereus): A century-old mystery solved.

Abstract

The Australian giant wood moth, Endoxyla cinereus (Cossidae), is a major forestry pest whose later instars bore into the trunks and branches of Eucalyptus, but the early larval stages have remained unknown for over a century. Using DNA analysis, we identified larvae collected from galls formed by scale insects (Apiomorpha spp.), as En. cinereus. This relationship was tested by rearing over 100 000 neonate larvae on alternative potential food resources including active galls of scale insects (Apiomorpha munita and A. crispa). Only larvae assigned to galls fed and developed into later instars. The complete life cycle of this moth was also confirmed by rearing a gall-fed larvae to adulthood over 2 years after establishment in a tree (Eu. tereticornis). This two-phase developmental strategy explains how larvae bridge the large size gap between hatching and tree establishment and provides a mechanism for the high reproductive output and dispersal bottlenecks of this species.