Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

FNZ 33 - Moranilini (Hymenoptera: Pteromalidae: Eunotinae) - Popular Summary

Berry, JA 1995. Moranilini (Insecta: Hymenoptera). Fauna of New Zealand 33, 82 pages.
( ISSN 0111-5383 (print), ; no. 33. ISBN 0-478-04538-7 (print) ). Published 08 May 1995


The moraniline wasps are a small group, both in number of species (64 described worldwide) and in their individual size: at 1-3 mm in length they are little bigger than a large pinhead. They are rather distinctive within the larger group of mostly parasitic wasps known as the chalcidoids. Even though most species are fully winged, one-third of the endemic New Zealand species have reduced wings.

Owing to their abundance and diversity, and the problems inherent in studying such minute insects, the chalcidoid fauna of New Zealand is poorly known. Until recently only five species of Moranilini had been recorded from New Zealand. Now seventeen species in three genera are recognised, of which eleven are found nowhere else and are assumed to be endemic. The other six species are found also in Australia.

Despite their small size and relative scarcity, moraniline wasps are interesting because of their life history and their restricted distribution. They occur naturally only in the region between New Zealand and India, with the greatest number and diversity of species in Australia. It is likely that the Moranilini were derived in Australia from chalcidoid ancestral stock, and that their diversity in this part of the world is due to their evolution in isolation here.

With a few exceptions the moraniline wasps are natural enemies of Coccoidea, a group including scale insects, mealybugs or pseudococcids (see Fauna of New Zealand no. 11), and giant mealybugs or margarodids (see Fauna of New Zealand no. 21). Most moranilines are primary parasitoids of coccoids. This means that the female wasp lays an egg inside the body of the host insect, where it hatches into a larva. This larva feeds on the host's body tissues until eventually the host is killed. After pupating inside the empty skin of the host, a new adult wasp emerges. (Note that a parasitoid kills its host, whereas a parasite usually does not.)

A few moranilines are predators, living in the woolly egg-sacs produced by female mealybugs and feeding on her eggs. These species pupate inside the egg-sacs, emerging as adults which seek out further mealybugs in which to continue the life cycle.

A very small number of moraniline species act as hyperparasitoids, developing inside the body of a parasitoid of another species which is itself developing inside the host insect.

The host insects are plant sap feeders, and some introduced species - particularly of mealybugs -can become pests in horticultural situations. They are hard to control with insecticides, because the adult females cover themselves in waxy secretions, and tend to occupy sheltered places on their host plants. Natural enemies such as moraniline wasps can be used as biological control agents, to reduce their numbers.