Distribution and abundance of endemic coelostomidiid scale insects (Hemiptera: Coelostomidiidae) in Auckland forests, New Zealand

Sap-feeding insects can excrete considerable quantities of sugar-rich honeydew. In New Zealand, South Island beech (Nothofagus spp.) forests are shaped by the extensive honeydew resource produced by two endemic coelostomidiid species (Ultracoelostoma assimile and U. brittini) and geckos on northern islands are known to feed on the honeydew of a third endemic coelostomidiid, Coelostomidia zealandica. There are six other endemic coelostomidiid species in New Zealand that utilise a range of plant hosts but the ecological role of these species is poorly understood. A survey of mainland forests in the Auckland Ecological Region was conducted in February–April 2006 to investigate the distribution and abundance of coelostomidiids in this area. Three coelostomidiid species were detected in the survey (C. zealandica, C. pilosa and C. wairoensis) and five new host–scale insect associations were identified. C. zealandica was uncommon, C. pilosa was widespread in broadleaved–podocarp forest but only formed light infestations, and C. wairoensis was present in all teatree stands examined, often forming heavy infestations on kânuka (Kunzea ericoides). Infested kânuka trees had sooty moulds growing on them and exotic wasps were regularly seen feeding on C. wairoensis honeydew. The extent and intensity of C. wairoensis infestation on kânuka suggests it will have community-level impacts.