Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

FNZ 35 - Pentatomoidea (Heteroptera) - Popular Summary

Larivière, M-C 1995. Cydnidae, Acanthosomatidae, and Pentatomidae (Insecta: Heteroptera): systematics, geographical distribution, and bioecology. Fauna of New Zealand 35, 112 pages.
( ISSN 0111-5383 (print), ; no. 35. ISBN 0-478-09301-2 (print) ). Published 23 Nov 1995


The superfamily Pentatomoidea includes several families of generally shield-shaped true bugs with a world fauna of several thousands of species. Three families are represented in New Zealand, which has a relatively small fauna - 16 species plus 2 subspecies - compared to larger or warmer regions.

The Cydnidae are usually shining black or brown bugs burrowing in the soil and feeding on roots, stems, or fallen seeds. Two species occur only in New Zealand, and two occur also elsewhere in Australasia. The endemic species Choerocydnus nigrosignatus lives in threatened habitats such as coastal sand dunes, inland flood plains, and depleted tussock grasslands.

All four species of Acanthosomatidae in New Zealand are endemic. Species of Rhopalimorpha inhabit grasses, rushes, and sedges in open habitats bordering streams or marshes, often at the forest edge, from coastal to subalpine environments, including tussock grasslands. Eggs are laid among developing seeds or on the underside of leaves of plants such as cutty grass. The five immature growth stages are usually spent among the seeds of the host plant, which serve as food. The single species of genus Oncacontias is our only shield bug inhabiting native forest.

Eight species of Pentatomidae can be found in New Zealand. Two are endemic, and two others are native to New Zealand but occur also elsewhere in Australasia and parts of the South Pacific. The remaining four have been introduced here. One of them, the green vegetable bug Nezara viridula, is an important and cosmopolitan pest on a wide range of economically important crops. Most Pentatomidae feed on plant juices, and live above ground on their host plants. Some species are destructive to cultivated plants. One group of species is predaceous, and its New Zealand members are important and beneficial predators on destructive insects.

In New Zealand there is apparently one generation per year in most pentatomid species. Winter is generally passed by the adult stage, sheltering in crevices of plants and grass clumps or under bark, rocks, leaves, and other objects. The majority of species are not hostplant-specific, but in some instances the life cycle is quite intimately linked with cer-tain plant genera, e.g., Coprosma or Pittosporum.

Mating generally occurs in spring and/or summer, depending on the species. Barrel-shaped eggs are laid in tight clusters glued to the host plant, usually on the underside of leaves. After hatching, young shield bugs often stay together, clinging to the empty egg-shells until they moult. Nymphs of the second instar (growth stage) then disperse in search of food. Nymphs moult five times to become adults. Shield bugs have a number of enemies, several of which are tiny wasps or flies that parasitise the eggs.

Probably the most distinctive shield bug in New Zealand is Hypsithocus hudsonae. Its relationship to other Southern Hemisphere Pentatomidae is unclear, and very little is recorded about its life history and habits. It is known from only five populations distributed separately in subalpine and alpine environments on the South Island. Males were unknown until quite recently. The species has limited ability to disperse - only males have long forewings, and both sexes lack hind wings - and occupies habitats that are considered to be at risk.