FNZ 35 - Pentatomoidea (Heteroptera) - Introduction
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
ZooBank: http://zoobank.org/References/ED0686ED-A8A6-42C2-AEFA-CDDBE9BF001D
INTRODUCTION
The Pentatomoidea or shield bugs include several families of generally shield-shaped Heteroptera with a prominent, large, and usually triangular scutellum which reaches to and beyond the apex of the clavus.
The families Cydnidae, Acanthosomatidae, and Pentatomidae have been recorded from New Zealand. Adults of these families have five-segmented antennae (except some Cydnidae and extra-New Zealand Pentatomidae) and bi- or tri-articulated tarsi. Nymphs have four-segmented antennae and three pairs of scent gland openings located dorsally on the abdomen between segments 3/4, 4/5, and 5/6.
The most comprehensive treatment of these families for New Zealand has been that of Woodward (1953, 1956), which included a key to the described species, descriptions of new taxa, and additional comments on a number of described taxa, but his work was not of a revisionary nature. The present study is based on over 3300 specimens from twelve New Zealand and overseas collections, and is the first comprehensive revisionary treatment of these groups for New Zealand.
The Cydnidae or burrowing bugs comprise about 400-600 species worldwide. Cydnids are characterised mainly by having fringes of close-set, rigid setae at the apex of the middle and hind coxae, and spiny legs. They are usually shining black or brown bugs burrowing in the soil and feeding on roots, stems, or fallen seeds, and are often attracted to artificial light in large numbers.
Classical treatments of the family are Stal (1876) and Signoret (1881-84). A rationalised classification of the Cydnidae has been published by Dolling (1981), although many modern treatments also follow Froeschner (1960). Four species of the subfamily Cydninae occur in New Zealand.
Aethus thoreyi (Signoret) is here transferred from the genus Cydnus, and is recorded from New Zealand for the first time. It occurs also in eastern Australia, and may have been recently introduced (accidentally) into New Zealand. Very little is known about its biology and distribution. Apparently nothing has been written on it since its original description in 1882.
Chilocoris neozealandicus Larivière & Froeschner is the only Chilocoris species known from New Zealand, where it is endemic; four species occur in Australia. The genus contains some thirty or more described species, but is mainly restricted to the Old World, where it has been reported from Asia south into Africa, including Madagascar.
Choerocydnus nigrosignatus F.B. White is also apparently native to New Zealand, and quite possibly endemic, although it may also occur in Australia.
Philapodemus australis (Erichson) is native to both Australia and New Zealand, and is also found in New Caledonia and in the Oriental region.
Pangaeus scotti Signoret is an Australian species. Previous workers have reported its occurrence in New Zealand, but it was apparently confused with C. neozealandicus. Among all material examined for this study, nothing supports the occurrence of P. scotti in New Zealand.
Very little is known about the habits of the New Zealand species, but limited observations suggest that they are univoltine. Eggs are apparently laid on or in the soil, and nymphs probably enter the ground to feed on the roots of plants or, in the case of P. australis, may feed on fallen grass seeds on the ground. The degree of host specificity, as for the majority of Cydnidae, is unknown. The biology of P. australis has been thoroughly studied in Australia by Hickman (1978), but it is not known whether these results apply equally in New Zealand.
Burrowing bugs are of no known economic importance in New Zealand.
The Acanthosomatidae have been variously treated as a full family or as a subfamily or tribe of the Pentatomidae. The current practice is to afford them family status. A world revision and classification, with keys to genera, has been published by Kumar (1974).
These shield bugs, of which about 200 species are known worldwide, are usually less strongly sclerotised than most Pentatomidae and have two-segmented tarsi. Four species occur in New Zealand, all endemic.
The genus Rhopalimorpha includes three species that are endemic to New Zealand and a fourth from eastern Australia - suggesting a Gondwana origin for the group. Rhopalimorpha lineolaris Pendergrast and R. obscura Dallas are widely distributed species occurring mainly on grasses, rushes, and sedges in open habitats. Their life histories are probably the best documented among New Zealand pentatomoids, owing mainly to the work of Pendergrast (1950, 1952, 1960). Rhopalimorpha alpina Woodward is an alpine species with a disjunct distribution on the South Island. Practically nothing is known of its life history; indeed, very little is known about any Heteroptera of alpine environments in New Zealand.
New Zealand acanthosomatids are apparently univoltine. Eggs are laid on the undersurface of plant leaves, and nymphs undergo five metamorphoses before becoming adults. Nymphs and adults are phytophagous, on various shrubs and trees (Oncacontias) or on lower-growing vegetation, usually on the seeds (Rhopalimorpha).
Pentatomoidea generally abandon their eggs immediately after oviposition. In several Acanthosomatidae, however, the female broods the eggs and guards the young nymphs, but this phenomenon has not been studied in New Zealand.
Oncacontias Breddin, with its single species O. vittatus (Fabricius), is endemic to New Zealand. It is widely distributed, occurring mainly on trees and shrubs. O. vittatus can be regarded as the only true forest dweller among New Zealand pentatomoids.
Acanthosomatids are of no known economic importance in New Zealand.
The Pentatomidae are the largest family of shield bugs, with about 5000 described species in the world. Unlike Acanthosomatidae, Pentatomidae have three-segmented tarsi. The most recent generic classification on a larger scale is that of Rolston et al. (1979, 1980, 1981, 1984) for the Western Hemisphere. There is also a cladistic analysis of the tribes of Pentatomidae (Hasan & Kitching 1993). No other consensus on the higher classification of Pentatomoidea below the family level is currently available.
The majority of species are phytophagous, and live above ground on their host plants. Some species are destructive to cultivated plants. One group is predaceous, and its New Zealand members are important beneficial predators on destructive insects.
Two species of predaceous pentatomids occur in New Zealand. They are characterised by their rostrum, which is directed away from the head and has the first segment robust and thick, apparently an adaptation to their predatory habit. Although adults are essentially predaceous, first-instar nymphs also feed on plant juices.
Cermatulus nasalis nasalis (Westwood) is native to both New Zealand and Australia. In New Zealand two endemic subspecies are recognised: C. nasalis hudsoni Woodward, which occurs only on the South Island at altitudes of 1200 metres or more; and C. nasalis turbotti Woodward, which is endemic to the Three Kings Islands. C. nasalis nasalis has been recorded from a wide range of native and introduced bushes and trees, and has been noted feeding on larvae of various pest insects such as Paropsis charybdis, a defoliator of Eucalyptus.
Oechalia schellenbergii (Guérin) occurs also in Australia and most of southern Oceania, and is probably one of our most important beneficial insect. It occurs on a wide variety of plants, especially introduced ones including crops, and like C. nasalis is an important predator of noxious insects such as caterpillars (including armyworms) and chrysomelid larvae.
The other species occurring in New Zealand are apparently strictly phytophagous; the rostrum has the first segment more slender, and not directed away from the head.
Dictyotus caenosus (Westwood) occurs in Australia and, probably as an introduction, in New Caledonia as well as in New Zealand. It is probably the species most commonly encountered when collecting by general sweeping or beating. It is occasionally noxious to lucerne seed crops on the South Island.
Glaucias amyoti (Dallas) occurs also in Australia, on Lord Howe Island, and in New Guinea. It is about the same size and colour as Nezara viridula (L.), and can sometimes be confused with it at first glance, but a close examination of head microsculpture, pronotum shape, and scutellum coloration offers a quick diagnosis. In New Zealand its life history is closely associated with plants of the genus Coprosma (Rubiaceae).
Four species of Pentatomidae have been introduced into New Zealand, namely Cuspicona simplex Walker, Dictyotus caenosus, and Monteithiella humeralis (Walker) from Australia, and Nezara viridula, a cosmopolitan species. All four are doing rather well here. Monteithiella humeralis has a close association with plants of the genus Pittosporum (Pittosporaceae). It has not been noted to pose any economic threat to fruit trees in New Zealand. Cuspicona simplex is strongly associated with solanaceous plants, especially the genus Solanum, to which it is noxious, although it is not usually a serious pest of tomatoes or potatoes. Nezara viridula is an important pest on a wide range of economically important vegetables including beans, cauliflower, marrow, potato, pumpkin, rhubarb, silver beet, sweetcorn, tamarillo, tomato, and turnip.
In New Zealand there is apparently one generation per year in most pentatomid species (two or three in Nezara, and perhaps also in Cuspicona). Overwintering is generally by the adult, in the crevices of plants and grass clumps or under bark, rocks, leaves, and other objects, especially on the ground. The majority of species are not host-specific, but in some instances the life cycle is quite intimately linked with certain plant genera. Mating occurs in spring and/or summer, depending on the species; barrel-shaped eggs are laid in tight clusters glued to a host plant, usually on the underside of leaves. After hatching, the first instars often are gregarious and stay clinging to the empty egg-shell until they moult and the second instars disperse in search of food. Nymphs undergo five metamorphoses to become adults.
Hypsithocus Bergroth is endemic and contains only one species, H. hudsonae Bergroth. It has a restricted, disjunct distribution in subalpine and alpine environments in Central Otago. Only recently have male specimens become available for study. The relationship of Hypsithocus to other Southern Hemisphere genera is still unclear. Almost nothing is known of the life history and habits of H. hudsonae, despite the fact that it is probably the most unique New Zealand pentatomid.
Pentatomoids have a number of natural enemies, several of which are hymenopterous or dipterous egg parasites.
The scent glands in adults are located in the metathorax, and open on the metapleuron through an opening termed the ostiole. In nymphs the scent gland openings are paired and located dorsally on the abdomen. The relative position of these openings and their structure are often useful in diagnosing nymphs at various level of classification. The scent gland secretions have been chemically analysed for several species around the world, but not in New Zealand. They appear to play a role in discouraging or even harming potential predators, but it has also been suggested that they may primarily serve as alarm or aggregation pheromones.
Pentatomoids are diurnal, but can be attracted to artificial light, and have been reported from high elevations. For example, specimens have been collected that had been wind-blown to the top of high mountains such as Mt Ruapehu in the central North Island. Species such as Hypsithocus hudsonae or Rhopalimorpha alpina occur only on mountain tops.