Summary

Present knowledge of the New Zealand mosquito fauna (Culicidae) is briefly reviewed. The existing species are listed, with annotations, and a key to the last instar larvae is provided. Recent publications relating to the New Zealand fauna are listed.

Introduction

The family Culicidae is treated here as including only the true mosquitoes. The non - biting midge families Dixidae and Chaoboridae, which are sometimes included as subfamilies of the Culicidae, are excluded. The New Zealand species belong to the subfamily Culicinae, the other two subfamilies usually recognised in the Culicidae (Anophelinae and Toxorhynchitinae) being absent.

The developmental stages of most of the native species are known with the exception of the eggs of some species and the larvae of the two species of Coquillettidia Dyar. Detailed descriptions and figures of most of the species are available and should be consulted in the publications of Belkin (1962, 1968). References to the literature up to the date of its publication are given in Belkin's (1962) work. The scope of subsequent papers, which are listed at the end of the present paper, is sufficiently page 168 indicated by their titles. References to recent descriptions of the developmental stages are given, for each species, in the faunal list below.

A key is given to the larvae, since this stage is most likely to be encountered in ecological investigations. The males are often most readily obtained by rearing from the larvae or pupae, and both sexes obtained in this way can be correlated with their larvae without possibility of error. Techniques for the collection, rearing, and study of mosquitoes are given in the paper by Belkin et al (1965).

Morphology, Physiology, and Ecology

Adult mosquitoes are distinguishable from nearly all other Diptera Nematocera in New Zealand by the possession of a long slender proboscis. The only insects likely to be confused with them are two rather rare rostrate species of Elephantomyia Osten Sacken (Tipulidae) which differ from the mosquitoes in venation. The sexes in the Culicinae are distinguishable by differences in the external genitalia and, with some exceptions, by the longer maxillary palpi and strongly plumose antennae of the males.

The pupae are comma-shaped in lateral view. The large cephalothoracic region bears laterally on the dorsum two respiratory organs (trumpets), and the abdomen bears two terminal paddles which enable the pupa to ascend to or descend from the water surface. The pupae of the Dixidae and of some Chironomidae which may be found in the same ground pools are similar to those of the Culicidae but usually differ in the form of the trumpets and paddles.

The larvae of the Culicinae are likely to be confused only with the, so far unknown, larvae of a rare species of Corethrella Coquillet (Chaoboridae). The known larvae of this family also possess a notably wider thorax, a subterminal respiratory siphon on the abdomen and anal gills, but lack mouth-brushes and have prehensile antennae which are inserted close together on the front of the head. The fully grown larvae of the largest native mosquitoes may be up to 12 mm. in length. The four larval instars are generally similar except in size. Most larvae move freely in the water, from which they filter micro-organisms and organic particles by means of their mouth brushes. None of the native species has predacious larvae. Most of the larvae breathe at the water surface through the respiratory siphon, but those of Mansonia Blanchard and Coquillettidia insert their modified siphons into the submerged stems or roots of aquatic plants and obtain air from the plant tissues.

The eggs are usually elongate-ovoid or fusiform in shape and about 1 mm in length. Those of Culex L. and of some species of Culiseta Felt and Mansonia and Coquillettidia are aggregated into rafts which float on the surface of the water Those of most other page 169 genera are laid singly on the water, on mud, or on the sides of receptacles containing water. Some are resistant to drying and hatch when again submerged in water.

An extensive literature exists and there is much detailed information on the physiology and habits of mosquito species — particularly those, like Anopheles spp. and Aedes aegypti L., which are important disease vectors. The only native species which has been investigated in any detail is Opifex fuscus Hutton (McGregor 1963, 1965; Haeger and Provost 1965; Provost and Haeger 1967), which is remarkable for its morphology and the unusual habit of the males of capturing the female pupae before the emergence of the female.

Under summer temperature conditions the duration of the egg and pupal stages of the more common native species may be only two or three days, and that of the larval stage two or three weeks. Lower temperatures slow the rate of development. Most species probably breed throughout the year but with greatly slowed larval development during winter. None of the native species is known to have an obligatory winter diapause in any developmental stage, though the adults of Maorigoeldia argyropus Walker have been reported to live through the winter in the northern part of its range. Few or no species breed above 2,000ft. and none above the bushline.

Most species breed in standing water in pools on the ground. In the larger permanent bodies of water, which are likely to have a varied predator fauna, the larvae are usually marginal or in areas where weeds or algal mats afford protection. A few species may occur amongst vegetation in small slow-flowing streams or ditches, or at the sides of larger rivers. Culex pervigilans Bergroth, in particular, rapidly takes advantage of temporary ground pools caused by disturbance of the soil by man. Most species breed in fresh water but several are confined to saline or brackish water. One species breeds in thermal areas in highly mineralised water which may be warmer than normal. Two species breed in treeholes and one breeds in water-holding leaf axils of terrestrial or epiphytic plants such as Collospermum spp. None is so far recorded from crab-holes.

The reduction in the size of the anal gills in species living in water with a high mineral content is apparently correlated with their osmoregulatory function. The shortened gills of the Culex in thermal waters suggest recent derivation from a more elongate form like that of C. pervigilans, but the semi-globose gills of the Aedes spp. of saline waters appear to be a longer - established character. The large size and more abundant tracheation of the gills of Maorigoeldia argyropus is apparently correlated with the longer submergence periods of this larva and an increased function in extracting oxygen from the water.

Only the females take blood meals and they may obtain these from man, animals, or birds. There are also records, outside New Zealand, of their biting fish (mudskippers) and frogs. Both sexes, however, may feed on plant secretions such as nectar. It is not known for most of our species whether a blood meal is a prerequisite to the maturation of the eggs, but Opifex fuscus can lay its first batch of eggs without a blood meal (Haeger and Provost, 1966). Not all species are attracted to man or come indoors. Most are night biters, except A. notoscriptus.

The duration of adult life of most species is not known precisely.

There is no evidence that the flight range of any of the native species is more than one or two miles.

None of the common endoparasitic organisms in mosquito larvae elsewhere (fungi such as Coelomomyces, protozoa such as Thelohania and nematodes such as Agamomermis) is recorded in New Zealand. An ectoparasitic mite and an epizoic ciliate protozoan (Vorticella) have been recorded on the larvae. There is no record of endoparasites of the adults in New Zealand. A mite occurring on adults may be ectoparasitic or phoretic. The most effective natural control of larvae and pupae is attributable to the larger predators such as ducks, frogs, fish (Galaxias, Gobiomorphus), aquatic Hemiptera (Anisops, Notonecta), and aquatic Coleoptera (Rhantus).

Pest Species, Disease Vectors and Control

Most of the native species are nocturnal biters which cause some annoyance to man and also to domestic animals. None of the major mosquito-transmitted diseases such as malaria, filariasis or dengue fever is endemic in New Zealand. The anopheline vectors of malaria are absent, and while some of the existing culicine species might act as vectors of filariasis or dengue, temperature and other conditions in New Zealand are probably unsuitable for the maintenance of an endemic cycle of transmission of these diseases. The first record of an insect borne disease of man and animals in New Zealand is that of Ross et al (1963). They demonstrated that Culiseta tonnoiri (Edwards) and Culex pervigilans were vectors of an arbovirus in Westland.

The control of mosquito breeding is usually achieved by the elimination of permanent breeding places by drainage, or by their periodic treatment with larvicides. Species which are vectors of disease, and enter dwellings may be attacked by the use of residual insecticide sprays in the dwellings. The breeding places of the predominant and most widespread pest species in New Zealand, Culex pervigilans, are well known and readily found, but those of Culiseta tonnoiri, a pest species throughout the West Coast of the South Island, have proved difficult to locate.

Relationships of the New Zealand Fauna

Three non-endemic species which have restricted distributions in New Zealand have been claimed as accidental introductions. This is probably true of the cosmopolitan Culex quinquefasciatus Say and may be true of Aedes australis (Erichson) and Aedes notoscriptus (Skuse), but is difficult to prove or disprove.

The geographical distribution of related species and genera outside New Zealand shows the New Zealand fauna to have affinities with those in areas to the north of New Zealand, especially Australia. There are no apparent relationships with the South American fauna. The endemic genus Opifex has long been considered to be primitive in its characters and the related subgenus Ades (Nothoskusea) may also be primitive. Belkin (1962) considered that the primitive element in the New Zealand Culicidae was more extensive and included the endemic genus Maorigoeldia, the endemic Austromansonia subgenus of Coquillettidia and the endemic species of Culiseta (Climacura). The latter subgenus has an unusual distribution (Australia, New Zealand and Eastern North America) which parallels that of the Amphibia (Amphicoela) and some plant taxa such as Thismia (Burmanniaceae).

Annotated Faunal List of New Zealand Culcidae

Key to Last-Instar Larvae of New Zealand Culicidae

(The general aspect of a culicine larva is illustrated by the text figure and the characters used in the key are indicated on various figures on the two plates.)

• (1) Siphon longer than wide, sub-cylindrical or truncate-conical; pecten teeth present, usually many in well-defined pecten; apical valves separate, small (Fig. 11). Lateral comb scales of 8th segment not in single row (except Culiseta. Antennae not longer than head, antennal hair at half-length or beyond.

• (2) Siphon as wide as long, fused with the valves; without pecten teeth; valves fused, as long as siphon, narrowed and denticulate apically (Fig. 2). Lateral comb scales in single row. Antennae twice as long as head, antennal hair at less than half-length (Fig. 3) (generic characters, larvae of the 2 New Zealand species unknown) Coquillettidia spp.

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MOSQUITO LARVA

• (2) Anal gills scarcely evident or small, not longer than wide, semi-globose (Fig. 4). (Siphon with 1 pair of ventro-lateral hairs)

• (3) Anal gills prominent longer than wide, usually tapering to pointed apex (Fig. 1).

• (3) Pecten with only 2 or 3 teeth; dorsolateral (middle) siphon valve with long hair (Fig. 6). Antennal hair single. Opifex fuscus Hutton

  Pecten with many teeth in definite row: dorsal-lateral siphon valve without a long hair. Antennal hair branched.

• (4) Pecten teeth in continuous series to nearly mid-length of siphon, their bases not contiguous (Fig. 7). Ventral brush with 9 pairs of hairs. Aedes (N) chathamicus Dumbleton Pecten teeth extending to about one-third length of siphon, basal teeth separate, distal teeth with bases contiguous. (Fig. 5). Ventral brush with 7 pairs of hairs. Aedes (H.) australis (Erichson)

• (5) Siphon with one pair of ventro-lateral hairs

  Siphon with more than one pair of ventro-lateral hairs, or several short median-ventral hairs.

• (6) Antennal hair and head-hair 5 both single (Fig. 8). Siphon index (length: width at mid-length) 2 (Fig. 9), shorter page 175

  

  PLATE 1: Scale-line — 0.5 mm for all figures; siphons in all figures in lateral view, dorsal to the left and ventral to the right, pecten tooth enlarged; heads dorsal view, left half, hairs numbered.
  FIG. 1: Mosquito larva, caudal segments of abdomen, lateral. Legend: 8, 8th segment; C, lateral comb; A anal segment; SA, saddle of anal segment; DG, dorsal gill; VG, ventral gill; SI siphon; P, pecten; VL, ventro-lateral paired hairs; V, valves. FIG. 2: Coquillettidia, siphon. FIG. 3: Coquillettidia, antenna. AH, antennal hair. FIG. 4: Aedes chathamicus, anal segment and gills, lateral. FIG. 5: Aedes australis, siphon. FIG. 6: Opifex fuscus, siphon. FIG. 7: Aedes chathamicus, siphon. FIG. 8: Aedes notoscriptus, head. FIG. 9: Aedes notoscriptus, siphon.

  page 176 or subequal to anal segment plus gills. Dorsal gill longer than ventral. Aedes (F.) notoscriptus (Skuse)

  Antennal hair and head-hair 5 both branched (Fig. 10). Siphon index 3, longer than anal segment plus gills. Dorsal and ventral gills subequal in length.

• (7) Pecten teeth extending in continuous series to near ventro-lateral siphon hair at mid-length (Fig. 11). Head hair 6 single (Fig. 10). Aedes (O.) antipodeus (Edwards)

  Pecten teeth in continuous series to one-third length, an isolated tooth near base of ventro-lateral siphon hair at two-thirds length (Fig. 12). Head hair 6 2-branched.

  Aedes (O.) subalbirostris Klein and Marks

• (8) More than 6 pairs of longer ventro-lateral siphon hairs, an equal number of long dorso-lateral hairs; siphon strongly tapered; 4-6 pecten teeth (Fig. 13). Anal gills rounded apically. Ventral brush with 1 pair of hairs. Antennal hair near mid-length, single. Head-hairs 5 and 6 many-branched (Fig.14). Maorigoeldia argyropus (Walker)

  Not more than 6 pairs of ventro-lateral siphon hairs, dorso-lateral siphon hairs, if present, very short; siphon slightly tapered; pecten teeth 8 or more. Anal gills with pointed apex. Ventral brush with at least 5 pairs of hairs. Antennal hair beyond mid-length, many branched. Head-hair 5 many-branched, 6 single or many-branched.

• (9) Scales of lateral comb in single row. Siphon with baso-ventral hair present; ventral siphon hairs in median line, unpaired; dorso-lateral hairs present; all hairs shorter than siphon width, single or 2-branched (Fig. 15). Head-hair 6 long, single (Fig. 16).(10)

  Scales of lateral comb not uniseriate, in sub-triangular area. Siphon without baso-ventral hair; ventro-lateral siphon hairs paired, longer than siphon width, branched; dorso-lateral siphon hairs absent. Anal gills without sub-basal constriction. Head-hair 6 many-branched.

• (10) Lateral comb with 18-20 scales; basal denticulations of pecten teeth 0-1; anal gills with sub-basal constriction.

  Culiseta (Cl.) tonnoiri (Edwards)

  Lateral comb with 25-29 scales; basal denticulations of pecten teeth 2-3; anal gills without sub-basal constriction.

  Culiseta (Cl.) novaezealandiae Pillai

• (11) Mental plate^* with 6-7 teeth on each side of median tooth (Fig. 17). Siphon straight-sided; 4 to 5 pairs of ventro-lateral page 177

  

  PLATE 2: (Scale-line — 0.5 mm for all figures (except Fig. 17); siphons in all figures in lateral view, dorsal to the left and ventral to the right, pecten tooth enlarged; heads dorsal view, left half, hairs numbered).
  FIG. 11: Aedes antipodeus, siphon. FIG. 12: Aedes subalfairostris, siphon. FIG. 13: Maorigoeldia argyropus, siphon. DL, dorso-lateral hairs. FIG. 14: Maorigoeldia argyropus, head. FIG. 15: Culiseta tonnoiri, siphon. BV, baso-ventral hair. MV, median ventral unpaired hairs. FIG. 16: Culiseta tonnoiri, head. FIG. 17: Culex pervigilans, mental plate. (Scale-line — 0.1 mm). FIG. 18: Culex rotoruae, siphon. FIG. 19: Culex pervigilans, siphon. FIG. 20: Culex asteliae, siphon. FIG. 21: Culex quinquefasciatus, siphon.

  page 178 hairs. Dorsal and ventral gills sub-equal in length. (12) Mental plate with more than 7 teeth on each side. Siphon straight or convex-sided; 4 pairs of ventro-lateral hairs. Dorsal and ventral gills equal or unequal in length. (13)

• (12) Siphon index 4.0-5.0; usually with 5 pairs of ventro-lateral hairs, pecten usually reaching basal hair (Fig. 18). Anal gills shorter than saddle. Culex (C.) rotoruae Belkin

  Siphon index 6.5-7.0; usually with 4 pairs of ventro-lateral hairs, pecten usually not reaching basal hair (Fig. 19). Anal gills much longer than saddle.

  Culex (C.) pervigilans Bergroth

• (13) Mental plate with 8-9 teeth on each side. Siphon straight-sided, index 8.5-10, pecten reaching one-sixth length (Fig. 20). Anal gills subequal in length. Culex (C.) asteliae Belkin

  Mental plate with 10-11 teeth on each side. Siphon slightly convex-sided, index not more than 5; pecten reaching one-third length (Fig. 21). Dorsal gill longer than ventral.

  Culex (C.) quinquefasciatus Say