Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

FNZ 50 - Heteroptera (Insecta: Hemiptera) catalogue - Popular summary

Larivière, M-C; Larochelle, A 2004. Heteroptera (Insecta: Hemiptera): catalogue. Fauna of New Zealand 50, 330 pages.
( ISSN 0111-5383 (print), ; no. 50. ISBN 0-478-09358-6 (print) ). Published 14 May 2004

Popular summary

True bugs (Heteroptera)

Heteroptera, or true bugs, are generally regarded as a suborder of the Hemiptera. There may be around 37 000 described species worldwide, and possibly another 25 000 species remaining to be described. The world fauna is divided into roughly 75 families. The number of species of better known continental faunas such as North America, Europe, or Australia, may be around 2 000 or 5 000 species. Compared with these larger regions the New Zealand fauna - currently comprising 29 families, 136 genera, and 305 species - may appear relatively small, but what it lacks in size it makes up in uniqueness, e.g., 82% of known species do not occur anywhere else in the world. From this point of view New Zealand can be regarded as a biodiversity "hot spot" for true bugs. Once described, the New Zealand fauna will probably reach 400 to 500 species. Faunal affinities are greatest with southeastern Australia.

The question of what is a true bug is not necessarily easy to answer since there may not be one unique defining character shared by all species. Nevertheless, it is probably possible to recognise most true bugs on the basis of three main characteristics: sucking mouthparts in the form of a segmented beak extending from the front of the head and running backward along its underside; slightly overlapping forewings lying almost flat over the abdomen; and each forewing base being much thicker than the tip (hence the name Heteroptera, derived from the Greek words heteros (different or other) and pteron (wing), referring to the nonuniform texture of the forewings).

While it is relatively easy to recognise a true bug, it may be more difficult to identify it at the species level. Heteroptera often show a high degree of morphological similarity within genera, high taxonomic diversity overall, and striking ecological preferences.

The Heteroptera are the largest and most diverse group of insects with incomplete metamorphosis. As such, their life cycle involves an egg stage, a series of nymphs (usually 5) or growing stages that look progressively similar to the adult, and finally an adult stage.

True bugs are a highly adaptable group that has managed to occupy most terrestrial as well as many aquatic and semi-aquatic habitats and to adopt remarkably diverse life habits on nearly all continents and most islands, suggesting a long evolutionary history for the group.

As a result, Heteroptera are well represented in New Zealand entomological museums and collections. Despite this, no up-to-date catalogue has been published following Wise's (1977) "... synonymic checklist of the Hexapoda of the New Zealand sub-region... ", which enumerated 100 genera and 170 species. Numerous name changes and new genera and species (over 160) have been published since then, and although the above checklist is still useful, it no longer reflects current knowledge of the fauna. Hence the reason for writing this new catalogue, which aims to answer the questions commonly asked about any group of insects: What, where, when, and how? What Heteroptera occur in New Zealand? What is their status (e.g., native, introduced from elsewhere, pests, beneficial predators)? What are the resources available to identify and study them? Where do species and genera occur (e.g., geographic distribution in New Zealand and overseas, habitats, dispersal abilities)? When are they active (e.g., seasonal activity, mating, egg-laying, wintering)? How do they live (e.g., food preferences, host plants, natural enemies)?

The majority of Heteroptera families occurring in New Zealand are terrestrial. Less than 7% of the fauna is semi-aquatic (living on or near water) or aquatic (living in water). Terrestrial species can be either mostly epigean (living on the ground), planticolous (living on low-growing, non-woody plants), or arboreal (living on trees and shrubs). The two native terrestrial habitats harbouring the greatest number of species are forests and shrublands (in the lowlands and on mountains). Tussock grasslands and open subalpine environments also harbour their own suites of unique species. In general, native species tend to live within the confines of native habitats, but many species also survive in modified environments. Introduced species seem to be able to invade natural habitats but, in general, only to a slight degree.

Very few native species live almost exclusively in coastal lowlands. On the other hand, most coastal sand dunes, estuarine habitats, and coastal wetlands are typically inhabited by introduced species. Some introduced species are synanthropic (living around human dwellings).

Very little is known about the life history of native true bugs. Host plants, or the plants on which true bugs breed and develop, have been confirmed for less than 25% of species, mainly in the seed bug and plant bug families. The seasonal activity of species, especially in the adult stage, is only becoming clearer in this catalogue with more data gathered from New Zealand collections. Adults are probably diurnal in most families, and although they may be active for most of the year, their peaks of activity are between November and March, that is, the end of spring (September-November), summer (December-February), and early autumn (March-May). The seasonal activity of immature stages as well as the breeding type of most species, i.e. the time of the year when they reproduce, are mostly unknown. Population biology and means of dispersal remain virtually undocumented.

The majority of Heteroptera found in New Zealand are phytophagous (plant-feeding) extracting sap directly from the plant vascular system (in most families), feeding on seeds, developing fruits or flowers, or sometimes pollen. The majority of species of the flat bug family are thought to feed on the mycelia or fruiting body of various wood-rotting fungi. Almost all families of Heteroptera also include species that are predacious on insects and other arthropods. There are also entire families that are predominantly predacious. Only the introduced bed bug is haematophagous (feeding on the blood of vertebrates, including humans); there does not appear to be any evidence of disease transmission.

Little is known about the natural enemies of New Zealand Heteroptera. Hymenopteran egg-parasites, some birds (e.g., pipits, rooks, starlings), spiders, damsel bugs, ground beetles, and mites have been observed as enemies of some true bugs in New Zealand, but published observations are few. The authors' field experience suggests spiders could be the most important predators, especially in open habitats such as tussock grasslands and alpine environments.

Economic importance, as generally perceived in terms of direct damage to crops or disease transmission by a single species, may be lower in Heteroptera than in other major insect orders, but it is documented for some native and introduced species in New Zealand (e.g., on various seed and vegetable crops, and tobacco). In addition, species with pest status in other parts of the world, including neighbouring island countries and other parts of Australasia, represent potential biosecurity risks for countries like New Zealand that rely heavily on primary industry for their economy. For example, chinch bugs and other species in the seed bug family have historically been among the most destructive plant-feeding pests in several countries of the world, hence the need to update the inventory of the New Zealand and neighbouring faunas through sustained fieldwork and taxonomic re-assessments.

As a group, Heteroptera can also serve humans and the environment in positive ways, especially those predacious species that can be useful biological control agents (e.g., in integrated pest-management programmes). In general, most predacious and zoophytophagous species native to New Zealand have not been investigated for use as biocontrol agents, although such true bugs have been used overseas to control thrips, mites, moth eggs and caterpillars, leafhoppers, mosquitoes, and planthoppers. In addition, seemingly economically unimportant groups of true bugs may be important to humans or to nature conservation. Aquatic Heteroptera, for example, may prove important both as foodstuffs for fish and as indicators of water quality.

Overall, about 25% of the fauna is flightless, but in flat bugs and a family of seed bugs flightlessness reaches 65-70%. Consequently, a large proportion of New Zealand species is limited in its dispersal abilities; many species are restricted in distribution not only to New Zealand but also to specific areas of the country, e.g., Fiordland, Northland, or northwest Nelson.

Little information is currently available on the abundance and distribution of supposedly rare species to establish their conservation status, but 65 species have now been identified that might be of conservation interest. However, it is only through quantitative investigations that more meaningful conservation assessments will be possible for these species; relying on casual observations or collections prevents any realistic approximation of population dynamics and distribution.

Information on New Zealand true bugs accumulated over the last 150 years is not easily accessible. It is most often scattered through the literature or still associated with specimens in biological collections. With this catalogue, the authors wish to provide specialist as well as non-specialist readers with a detailed overview of all available knowledge on the taxonomy, distribution, biology, and dispersal of New Zealand Heteroptera. The format of the catalogue has been developed with the interests of systematists and other biologists in mind. It should allow easy information retrieval, comparison between genera and species, and synthesis of data. The authors believe such a comprehensive database is necessary before testing hypotheses about environmental and other relationships in Heteroptera.