A Report on Material Obtained During a Mosquito Survey at Palmalmal, New Britain, July-October, 1945
[Received by the Editor, December 6, 1945; issued separately, March, 1946.]
Issued separately as Bulletin No. 1, Royal New Zealand Air Force Ento- mological Surveys. South-west Pacific, 1945. Authorised by Chief of Air Staff.
This study was made between 4th July and 26th October, 1945, while the writer was engaged on a mosquito survey at the R.N.Z.A.F. Station, Jacquinot Bay, New Britain.
Jacquinot Bay is situated on the southern coast of New Britain, almost a hundred miles from Rabaul. The present paper deals with material collected from the southern shore of the Bay and Cape Cunningham, which bounds it to the south. Particular attention was paid to the vicinity of Palmalmal, where the R.N.Z.A.F. station was established. All species mentioned were collected either in coastal coconut plantations or in bordering second-growth jungle and rain forest. No collections were made more than two miles from the shore, or at a greater elevation than 600 feet.
The earliest records of New Britain's mosquito fauna (Edwards, 1923; Hill, 1925) refer to material collected in 1922 by Hill and Heydon. These investigators gathered material at Rabaul and Toma on the north-eastern side of the Gazelle Peninsula, and at Beining on the western side. In November, 1933, Taylor (1934b) collected at Rabaul and at Pondo, midway along the western coast of the Gazelle Peninsula. In his paper Taylor made reference to Culicidae gathered at Rabaul by Backhouse and Bayley.
So far, thirty-three species of mosquitoes have been recorded from New Britain. Twelve species are here reported from the island for the first time. Their names are marked with an asterisk in this account. These additions bring the known mosquito fauna of New Britain to a total of forty-five species.
Previously collected in the Rabaul district, the following eight species were not collected during the survey:
|First published record from New Britain.|
|Hodgesia quasisanguinea Leicester, 1908*||Hill, 1925.|
|Ficalbia (Etorleptiomyia) elegans (Taylor, 1913)||Taylor, 1934b.|
|Aëdes (Macleaya) tremula Theobald, 1903||Taylor, 1934b.|
|Aëdes (Pseudoskusea) culioiformis (Theobald, 1905)||Hill, 1925.|
|Aëdes (Geoskusea) fimbripes Edwards, 1924||Edwards, 1924.|
|Armigeres obturbans (Walker, 1860)||Cooling, 1924.|
|Culex (Neoculex) brevipalpis (Giles, 1902)||Taylor, 1934b.|
|Culex (Mochthogenes) cataractarum Edwards, 1923||Edwards, 1923.|
[Footnote] * References to the literature on the toxonomy and synonomy of mosquito species mentioned in this report will be found in Cooling (1924) and Taylor (1934a).
Comparative rainfall figures over a period of six years (1925 and 1933–37) show the yearly average at Rabaul as 95.91 inches, and at Palmalmal as 205.27 inches. This very high figure for Palmalmal and other places on the southern coast of New Britain is explained by the fact that the south-east Trades, at their height from July to October,' lose much of their moisture content here in crossing the high ranges which run roughly parallel to this part of the coast. Pondo and Beining, on the western side of the ranges sheltering Rabaul, have almost as heavy a rainfall as the southern coast (over a period of eleven years, the yearly average was 176.72 inches); and, like Rabaul, have their wettest months from December till April, during the north-west Monsoon. (Comm. Aust. Bur. Meteorol., 1940).
Malaria was endemic in the native population at Jacquinot Bay. The malaria vectors present were Anopheles punctulatus punctulatus Dönitz and A. p. moluccensis (Swellengrebel and Swell. de Graaf). Adequate mosquito control measures, combined with suppressive atebrine therapy, kept the incidence of the disease at a minimum among R.N.Z.A.F. personnel. (Cilento, undated, a, gives an account of malaria in the Australasian Region.)
Dengue fever (Lumley and Taylor, 1943) was not reported from this area. Aëdes aegypti (Linnaeus), the principal intermediary host of this disease, was seldom encountered.
Potential vectors of filariasis included Anopheles p. punctulatus and A. p. moluccensis (Heydon, 1931; Backhouse, 1934); also Aëdes scutellaris (Walker) (Buxton and Hopkins, 1927; Cilento, undated, b), and Culex fatigans Wiedemann (Cilento, undated, b). Anti-mosquito measures (larvicidal treatment of breeding places, screening of water drums, puncturing and flattening of waste metal containers) kept these mosquitoes under control. No cases of filariasis were reported from the Station.
Among the important pest mosquitoes, two species of the genus Armigeres were most troublesome in the camp clearing in dull weather. On sunny days these insects were plentiful at the edge of the jungle, not venturing into the open until late in the afternoon.
Certain day-biting species, notably Aëdes alboscutellatus (Theobald), Aëdes carmenti Edwards and Aëdes similis (Theobald) were constantly present in great numbers in shady jungle. These mosquitoes have been found breeding in jungle pools of a very transient nature. Although jungle and rain forest at Palmalmal were thoroughly searched for their breeding places, developmental stages of such species were seldom or never discovered. The number of larvae collected was altogether inadequate to account for the huge numbers of imagines constantly encountered. It is suggested that an investigation of the fauna of water-retaining epiphytes and other potential breeding places in the forest canopy might yield significant information concerning the breeding habits of these shade-loving mosquitoes.
Throughout the survey, larvae were gathered from pools with a long-handled 250 cc. dipper, and from tree holes with a siphon of
rubber tubing. “Biting collections” of imagines were made with a chloroform killing-tube which was applied over mosquitoes when they settled on and commenced to bite the collector. Aquatic stages taken to the laboratory for study were reared individually in small petri-dishes under gauze-covered lamp chimneys. They were maintained in water from their own breeding places. This water was found to contain all the food materials necessary for their development, except in the case of predacious species, which were supplied with smaller larvae as food.
It is hoped that this study may be of value in bringing to light new locality records for mosquitoes not previously known from this part of the Australasian Region, and in affording some comparison with the results achieved by other investigators in the drier Rabaul district.
A collection representative of the material dealt with has been deposited at the Cawthron Institute, Nelson, New Zealand.
I wish to record my thanks to the Royal New Zealand Air Force for affording me the laboratory and other facilities which made this survey possible as part of the malaria control programme at Jacquinot Bay; to Group Captain Chisholm, O.B.E., R.N.Z.A.F., D.M.S. (Air), at the time of the investigation, and to the several Medical Officers under whom I worked overseas; to Major-General Sir Fred Bower-bank, D.G.M.S. (Army and Air), Wing-commander Forrest, O.B.E., R.N.Z.A.F., and Wing-commander Marsh, R.N.Z.A.F., present D.M.S. (Air), for making it possible for me to work on my field results after returning to New Zealand, to Victoria University College for the provision of laboratory facilities, and the interest and help afforded me by Professor Richardson; and to the Cawthron Institute, Nelson, for generous library facilities.
Anopheles (Myzomyia) punctulatus punctulatus Dönitz, 1901.
Larvae and pupae were commonly found in water bodies of a temporary nature. They were most abundant in pools devoid of any macroflora, that contained clear water and were exposed to direct sunlight. Wheel ruts and footprints in muddy ground, and blocked-up drainage ditches appeared ideal breeding places. The pools in which this mosquito was found were almost invariably man-made, and due to recent military activity. Once only, breeding was observed in natural seepage water at the foot of steep cliffs.
On the comparatively few occasions on which this anopheline was found in grassy ruts, Anopheles p. moluccensis was also present. Temporary pools without macroflora sometimes held Anopheles p. moluccensis (rarely), Uranotaenia quadrimaculata and Culex pullus, as well as A. p. punctulatus.
In the laboratory, second and later instars of A. p. punctulatus were several times observed to approach hatching eggs of their own species and eat the emerging larvae. They did this when supplied with their normal food in fresh samples of water taken from the surface of a natural breeding pool, as well as under starvation conditions. The same phenomenon was subsequently observed in densely populated pools in the field. In the absence of other significant
natural control factors, cannibalism becoming patent under overcrowded conditions would be instrumental in achieving the optimum population.
Many of the temporary pools dried up in prolonged periods without rain, and during spells of intermittent rain heavy down-pours flushed them out and destroyed most of the larval population by stranding. Under these conditions the duration of the aquatic life of A. p. punctulatus varied between 6½ and 9 days in the field (the egg and larval stages together averaged 5½ to 8 days in length, the pupal stage 1 day).
Adults of this species were seldom taken in night catches in the R.N.Z.A.F. area. They were not found in huts in daytime collections for resting mosquitoes in the native village of Manginuna on the coast of Cape Cunningham, or in a neighbouring camp of the Australian local administration.
Their absence from the R.N.Z.A.F. area was largely explained by the lack of breeding facilities in the vicinity, as the result of malaria control work. However, there was heavy anopheline breeding near the native villages mentioned above, and a high degree of malaria incidence among the natives themselves. The huts at Manginuna were of primitive type, small and ill-ventilated.—More often than not they were filled with smoke from a fire smouldering in the centre of the floor. Conditions at the other village went to the opposite extreme. Here the buildings were large and well-ventilated, and admitted the maximum amount of light. Thus in neither place did the huts afford favourable daylight resting places for anophelines.
Anopheles (Myzomyia) punctulatus moluccensis (Swellcngrebel and Swell. de Graaf, 1920).
This subspecies was collected at Jacquinot Bay over the whole period of the survey, and showed a wider habitat preference than did A. p. punctulatus. The aquatic stages were prevalent in water bodies exposed to direct sunlight, but with available shade and shelter in the form of marginal and emergent grasses, floating leaves and algae. In general, clear water seemed to be preferred, although at various times all stages of larvae and pupae were found in murky water—on one occasion in a foul pig-wallow, covered with an almost unbroken algal mat.
Wheel ruts of long standing, with a developing macroflora and macrofauna, formed the usual type of breeding place. Swamps, coral pits, blocked and grassed-over drainage ditches, stream backwaters with emergent vegetation, seepage pools, native wells, small tins and other metal receptacles in rubbish dumps, and even a rot hole in the limb of a tree, were all utilized by A. p. moluccensis.
Associated mosquitoes in breeding foci were:—In swampy areas: Bironella gracilis, Uranotaenia albescens, Culex fraudatrix and C. pullus; in wheel ruts and shallow ponds due to the amalgamation of such ruts: Anopheles p. punctulatus (occasionally), Culex halifaxi, C. cylindricus, C. fraudatrix, C. papuensis, C. pullus, C. annulirostris and Culex sp. nov.?; in temporary pools: Anopheles p. punctulatus
and Culex pullus; in tin cans: Aëdes scutellaris; and in a rot hole (the tree concerned being in a clearing near the beach at Cape Cunningham South, 3/4 mile along the shore from the nearest habitation): Aëdes albolineatus.
The larval and pupal stages averaged 10 and 1½ days, in laboratory-reared specimens.
Adults were occasionally taken biting in and near huts in the R.N.Z.A.F. camp, from 6.30–7 p.m. onwards.
Bironella (Bironella) gracilis Theobald, 1905.
The presence of this mosquito in New Britain was first reported by Hill (1925). Hill and Heydon found larvae in the backwash of a small mountain stream, a tributary of the Nambung River. In the water where these larvae were collected there was a considerable quantity of decayed vegetable matter (Taylor, 1929).
Lee and Woodhill (1944) questioned Hill's identification of this species, considering it more likely that his larvae belonged to the B. papuae series. Russell (1943) recorded the occurrence of B. papuae in New Britain, but did not state the source of his information or material.
In August and again in October, larvae of B. gracilis were secured in a Pandanus swamp on the coast about two miles south of Manginuna village. From these a single adult male was reared out, and the larval identification confirmed.
Larvae were not common, and the few collected were dipped from still water covered with floating debris—leaves and small scraps of rotting wood—at the base of emergent vegetation, chiefly young Pandanus.
The swamp had a well-developed macrofauna. This included small fish, tadpoles, dragonfly nymphs and water beetles. Other mosquito larvae present were those of Anopheles p. moluccensis, Uranotaenia albescens, Culex fraudatrix and C. pullus.
The adult male bred out was brought to the laboratory as a fourth instar larva 4.9 mm. in length. This larva pupated the day after collection, and the pupal stage lasted 2¼ days.
Megarhinus inornatus Walker, 1865.
Late instar larvae were found on several occasions in both clear and murky water held in coconut husks and small cans, in jungle bordering the Airstrip. At no time were more than three fourth instars found in the same small container. Only once was another mosquito species associated with M. inornatus in this type of breeding place. A solitary fourth instar larva of Tripteroides quasiornata and a few early instars of the same species were found on this occasion, in a coconut husk containing water foul with organic debris.
Towards the end of October, 42 second and third instars of M. inornatus were collected from about two litres of clear water held in a truck tyre that lay at the edge of the R.N.Z.A.F. clearing. Associated with them were many larvae of Aëdes scutellaris and Culex papuensis. Almost every M. inornatus larva was engaged in eating a larva of one of the other species present, when collected.
Specimens kept in the laboratory ate all other species of mosquito larvae supplied them, and were also cannibalistic.
After remaining in the fourth instar stage for 63 days, a larva collected in July finally pupated. A female imago emerged 4½ days later. Adult females of this species were occasionally captured flying inside buildings during the day, throughout the survey period. They made an exceptionally shrill buzzing noise, much louder than the sound made by most mosquitoes, while on the wing.
Tripteroides (Rachisoura) filipes (Walker, 1861).
Two late instar larvae were siphoned from about 10 cc. of clear water held in the leaf axil of a Taro plant (Colocasia sp.) in a native garden near the coast, on 15th July. They were associated with larvae of Aëdes kochi.
*Tripteroides (Tripteroides) argenteiventris (Theobald, 1905).
In the latter part of July and during August, female imagines of this mosquito were often found flying about the collector in shady jungle. They seldom attempted to bite. Several specimens were captured resting a few inches above the ground, on the buttress of a large tree in rain forest.
Tripteroides (Tripteroides) bimaculipes (Theobald, 1905).
Larvae were collected from coconut husks containing water of a fairly high organic content in the middle of July. In early August, a few late instars were gathered from murky water in a rot-hole in the buttress of a rain forest tree. They were in association with the aquatic stages of Aëdes albolineatus.
Tripteroides (Tripteroides) quasiornata (Taylor, 1915).
Throughout the whole survey period larvae were found in coconut husks in shady places and in rot-holes in trees. The condition of the water ranged from fresh and clear to murky, with a high organic content. A single fourth instar larva was taken from a metal bucket of rain water.
On one occasion a fourth instar Megarhinus inornatus was found in the same husk as T. quasiornata larvae; and Aëdes albolineatus and A. scutellaris frequently shared the same breeding place.
Fourth instar larvae of T. quasiornata brought back to the laboratory tended to remain in this condition from a few days up to several weeks. The length of the pupal stage averaged four to five days.
Adult females attempted to bite throughout the day and were usually found on shady paths through high grass or in second-growth jungle. They formed only a small percentage of the day-biting population in such places, but individually were very vicious biters. Occasionally these mosquitoes entered huts in the late afternoon.
Hodgesia cairnsensis Taylor, 1919.
Only a few female imagines of this very small insect were encountered, during late October. They were captured in dense, shady jungle, and were very readily attracted to man.
*Uranotaenia albescens Taylor, 1914.
Early in July several larvae were dipped from among emergent grasses in the quiet backwater of a small stream, near the mouth of the Wunung River. A day or two before the collection was made, this watercourse had been swollen by heavy rains; so the larvae had very likely been swept from a breeding place further upstream. In the middle of October more larvae were secured, from a Pandanus swamp on Cape Cunningham.
In the July collection, Culex pullus was the only associated mosquito.
Developmental stages of Anopheles p. moluccensis, Bironella gracilis, Culex fraudatrix and C. pullus were also found in the swamp.
Uranotaenia argyrotarsis Leicester, 1908.
Larvae and pupae were numerous in limestone pot-holes in the ravine of a small tributary of the Kalumalagi River, when this locality was visited in late July. In the middle of August, a batch of late instar larvae were found in a rot-hole in the base of a breadfruit tree. This tree stood alongside a stream that flowed in a small limestone ravine half a mile from the coast at Palm Point.
The aquatic stages were very fast in their movements. They travelled in short dashes, and made straight for the bottom when disturbed. When at the surface these larvae tended to hang head downwards. In this respect they differed from other members of the genus, which usually assume a horizontal, anopheline-like position.
From laboratory observations over a small number of rearings, it was found that the larval stage averaged 7–10 days, and the pupal stage 2 days.
Neither in the laboratory nor in the field were adults of this species ever known to bite. From time to time throughout the period of the survey they were seen flying in shady rain forest in close proximity to streams. In the middle of October a number of specimens of both sexes were observed resting on a damp and shady limestone cliff, above a small waterfall, on a tributary creek of the Kalumalagi River.
Uranotaenia nigerrima Taylor, 1914.
A number of larvae and cast pupal skins were collected from clear water in a rusty tin, early in July. This was the sole occasion on which the species was encountered at Palmalmal.
Uranotaenia quadrimaculata Paine and Edwards, 1929.
Larvae occurred sparingly in a small swamp formed by seepage from the base of limestone cliffs. This locality was five miles from Cape Cunningham North and on the southern part of Jacquinot Bay. The species was collected on each of three visits to the swamp, from July to September. In the middle of July eight larvae were found in a half coconut husk filled with rather cloudy water. The husk lay under the shade of grasses at the edge of a disused track through Palmalmal plantation. At about the same time, and again during October, developmental stages were collected from clear water in an unshaded wheel rut at the side of the coast road near Manginuna village.
In the wheel-rut collections, Anopheles p. punctulatus and Culex pullus were found in association with U. quadrimaculata.
When the species was collected at Manginuna in July, two male imagines were seen to emerge in mid-day sunshine. The same evening, an adult female emerged from one of several pupae taken back to the laboratory. Early one afternoon in August, a female of this mosquito was captured flying near a roadside ditch in bright sunshine.
Aëdes (Finlaya) kochi (Dönitz, 1901).
Developmental stages were secured from July to September, usually in clear water held in the leaf axils of taro plants (Colocasia. sp.). Once they were found in a similar position in a young Pandanus. Tripteroides filipes was the only mosquito observed to share the breeding place of this species.
Larvae of A. kochi were never seen in coconut husks as reported by Hill (1925). The records of both Heydon (1931) and Taylor (1934b) show that they, too, were unable to find this mosquito in such a breeding place. Heydon found larvae of the species in leaf axils at Rabaul at about the time of Hill's visit. Husks at Palmalmal commonly contained the aquatic stages of Aëdes (Stegomyia) albolineatus. At first glance, larvae of this insect resemble those of A. kochi, for both species have conspicuous stellate hairs on the abdominal segments.
Adults were seldom encountered in nature. Occasionally female imagines were taken biting indoors in the evening, and for two or three hours after dawn.
Aëdes (Finlaya) notoscriptus (Skuse, 1889).
On the first of August, a pupa of this species was siphoned from water of high organic content in a rot-hole of a dead tree alongside the Airstrip. The specimen was taken to the laboratory, and three days later a female imago emerged. Towards the end of the same month another A. notoscriptus was obtained. This one was captured in the act of biting, during a morning collection in shady jungle.
*Aëdes (Finlaya) papuensis (Taylor, 1913).
A single pupa was taken early in August from rather cloudy water in a coconut husk on a rubbish heap. Two days after collection, a female imago emerged. A week later a number of larvae and pupae were secured. They were siphoned from clear water in a long, deep crack in a prostrate log, on the beach near the mouth of the Taut River. The pupal stage was found to average two to three days in duration. One larva taken as an early instar pupated two and a-half weeks after collection, a female imago emerging three days later.
Males from this batch appeared about twelve hours before the emergence of the first female. The females could not be induced to bite in the laboratory. Adults of this species were never observed in the field.
Aëdes (Stegomyia) aegypti (Linnaeus, 1762).
Larvae were taken from an uncovered water drum containing constantly-replenished rain water, during late August. The drum stood under the eave of a native hut at Tatongpal village, Cape
Cunningham South. The proper disposal of waste metal containers and the screening of water containers not in constant use effectively excluded this species from the vicinity of the R.N.Z.A.F. and other military camps in the district.
Aëdes (Stegomyia) albolineatus (Theobald, 1904).
This mosquito was the dominant tree-hole breeder at Jacquinot Bay throughout the period under review.
Although most commonly found in rot-holes in trees, developmental stages also occurred in coconut husks, beached canoes, and such artificial containers as tin cans and old army helmets. They were found in all types of water, from clear and fresh to murky and foul with organic debris.
In rot-holes the larvae were sometimes associated with Tripteroides bimaculipes, and on one occasion Anopheles p. moluccensis was present; in coconut husks, with Tripteroides quasiornata, Aëdes scutellaris, Armigeres lacuum and A. breinli; in beached canoes, with Aëdes scutellaris and Culex fatigans; and in tin cans, with Aëdes scutellaris.
Imagines could usually be found in shady jungle during the day.
Aedes (Stegomyia) scutellaris (Walker, 1859).
This species occurred in much the same types of breeding places as Aëdes albolineatus, but was more “domestic” in nature than that species. It was most often collected from coconut husks, and artificial containers in general. Pockets of water in wrecked aircraft and trucks, rubber tyres and old tarpaulins were always prolific sources of breeding. Water containing larvae of this species was usually clear and fresh, but specimens were occasionally found in water of high organic content.
The following mosquitoes were found in association with A. scutellaris:—in tree holes: Tripteroides quasiornata; in coconut husks: Tripteroides quasiornata, Aëdes albolineatus, Armigeres lacuum and A. breinli; in rather rusty water in the tray of an abandoned truck: Culex pullus; in beached canoes: Aëdes albolineatus and Culex fatigans; in tyres: Megarhinus inornatus (once only) and Culex papuensis (once only); and in tin cans: Aëdes albolineatus and (rarely) Anopheles p. moluccensis.
Imagines bit readily, and on sunny days they were sometimes troublesome just within the shade of jungle. Until dumps of husks and waste metal cans were removed from the camp area these mosquitoes were often taken biting inside buildings, particularly on dull days.
The species was especially plentiful in the vicinity of native villages, where there was an abundance of suitable breeding places in the form of canoes and unscreened water containers.
Because of the semi-domestic habit of A. scutellaris, its degree of abundance within the Station bounds formed an excellent check on the efficiency with which general mosquito control measures were being carried out.
Aëdes (Aëdimorphus) alboscutellatus (Theobald, 1905).
Although developmental stages were never secured, female imagines formed an important section of the day-biting population in shady jungle and rain forest at Palmalmal.
* Aëdes (Aëdimorphus) imprimens (Walker, 1861).
Imagines were collected twice only, in early July and the middle of September. They were taken in shady jungle, in the act of biting.
* Aëdes (Aëdes) carmenti Edwards, 1924.
Numbers of this species could always be found, biting during the day in shady jungle and rain forest. Towards evening the mosquito was sometimes taken in huts near to the jungle's edge.
Aëdes (Aëdes) funereus (Theobald, 1903).
Females were often encountered biting in shady jungle during the day. They seldom occurred in any numbers more than a few hundred yards away from the coast. During July and August the species was particularly abundant in a swampy area of Pandanus bordering the sea beach, a little south of Manginuna village.
Aëdes (Aëdes) funereus var. ornatus (Theobald, 1905).
This mosquito usually figured in daytime biting collections from jungle bordering the Station. It was locally the dominant species in a swampy patch of partly cleared rain forest between the Airstrip and the coast.
* Aëdes (Aëdes) similis (Theobald, 1910).
Females of this species regularly made up the greater part of the jungle and rain forest day-biting mosquito population. Vicious and persistent biters in shady places, these insects could be found right to the edge of the Station clearing. They were never taken in huts or in the open.
* Aëdes sp. nov.?
A single imago was captured in the act of biting, in the middle of September. It was encountered in swampy rain forest to seaward of the Airstrip. A medium-sized dark brown insect with a silver-scaled scutellum and white-banded tarsi, the mosquito had a number of larval hydrachnid mites clustered about its thorax and the ventral part of its abdomen.
Genus ARMIGERES Theobald, 1901.
Two members of this genus were abundant at Jacquirot Bay. They were the most troublesome pest mosquitoes in cleared areas.
In the early stages of occupancy of the Station, husks that littered the partly-overgrown coconut plantation were found to be swarming with developmental stages of these insects. Imagines, particularly of Armigeres lacuum, were very numerous. Next to Aëdes similis, they were the most plentiful day-biting mosquitoes in shady jungle. Although rarely found in the open in sunny weather, they were abundant throughout the area on dull days. At all times of day, regardless of weather, they were a pest in huts, messes, ablution blocks and showers—in fact, in all camp buildings that offered both a shady resting place and a ready food supply. The greatest numbers of these mosquitoes were encountered between about 4 p.m. and dusk.
As waste-disposal arrangements improved and coconut husks were gathered together and destroyed as breeding places, the population of the Armigeres pest was curtailed to some extent. Significant numbers of these insects still remained, as breeding persisted in husks and rotting stumps concealed in the jungle surrounding the Station.
Armigeres lacuum Edwards, 1922.
Larvae were generally found in coconut husks containing copra in an advanced state of decomposition. Frequently they were collected from water of a high organic content in the rotting stumps of small trees, more rarely from tin cans, and once from clear water in an aircraft tyre lying in thick grass at the edge of a jungle clearing. When the water in husks was not of too high an organic content, Aëdes albolineatus and Aëdes scutellaris were sometimes found in association.
Larvae answered closely to the diagram and description of Armigeres milnensis published by Lee (1944), apart from the fact that the number and arrangement of hairs in the lateral comb were more variable in Armigeres lacuum.
Under laboratory conditions the length of the larval stage varied between two and three weeks, and that of the pupal stage between two and four days. The males of any particular batch were observed to emerge some hours before the females; and the sex representation in a batch was approximately equal.
* Armigeres breinli (Taylor, 1914).
Breeding places of this insect were much as for the preceding species. Of very similar habits to Armigeres lacuum, it was much less common throughout the period under discussion.
Culex (Lutzia) halifaxi Theobald, 1903.
From August to October, larvae were dipped from clear water in grassy wheel-ruts about the whole area. A few specimens were collected from an uncovered water tank.
Frequently these predatory and cannibalistic larvae appeared in pools already occupied by other mosquitoes, notably Anopheles p. moluccensis, Culex fraudatrix and C. pullus. In such cases a noticeable decrease in the populations of these other species soon became apparent. Even in the presence of many larvae of other species, a C. halifaxi larva would not hesitate to attack one of its own kind when the opportunity was available.
The mosquito spent upwards of two weeks in the larval state, under laboratory conditions. The average duration of the pupal stage was two days.
Imagines were rarely encountered in the field, and were never observed to bite.
*Culex (Lophoceratomyia) cylindricus Theobald, 1903.
Aquatic stages were found during the whole period under review. Never very common, they were dipped from wheel-ruts of long standing, grassed-over ditches, swampy places, and on one occasion from a shallow well. Anopheles p. moluccensis, Culex fraudatrix and C. pullus frequented the same types of breeding place as this species.
Culex (Lophoceratomyia) fraudatrix Theobald, 1905.
This was a rather common mosquito at Jacquinot, Bay. Its larvae were collected from wheel-ruts, grassed-over drainage ditches, swampy areas, native wells and tree holes.
Associated with it were:—in wheel ruts: Anopheles p. moluccensis, Culex halifaxi, C. cylindricus and C. pullus; in drainage ditches: Anopheles p. moluccensis and Culex cylindricus; and in Pandanus swamp: Anopheles p. moluccensis, Bironella gracilis, Uranotaenia albescens and Culex pullus.
Imagines were occasionally encountered biting near breeding areas in the daytime. At the beginning of October one was taken at the light in the laboratory, just after nightfall.
*Culex (Culiciomyia) papuensis (Taylor, 1914).
At the close of August a few larvae were located in clear water in a small wheel-rut with marginal and emergent vegetation. About two months later a concentration of larvae up to third instars was found in clear water in a truck tyre that lay at the edge of the camp clearing.
Associated mosquitoes were:—in the wheel rut: Anopheles p. moluccensis and Culex pullus; in the tyre: Megarhinus inornatus and Aëdes scutellaris.
Culex (Culiciomyia) pullus Theobald, 1905.
This was by far the commonest species of the genus Culex at Palmalmal. It was abundant during the whole period of the survey. Breeding usually took place in clear water exposed to direct sunlight. Temporary pools of the kind preferred by Anopheles p. punctulatus were often utilized. Developmental stages were rarely found in artificial containers.
Associated mosquito species were:—in road ruts of a temporary nature: Anopheles p. punctulatus and Uranotaenia quadrimaculata; in road ruts of long standing: Anopheles p. moluccensis, Culex halifaxi, C. cylindricus, C. fraudatrix, C. papuensis, C. annulirostris and Culex sp. nov.?; in a stream backwater: Uranotaenia albescens; in shallow swamps: Anopheles p. moluccensis, Bironella gracilis, Uranotaenia albescens and Culex fraudatrix; and in the tray of an abandoned truck: Aëdes scutellaris.
C. pullus adults occasionally entered huts during the day and early evening, but did not prove troublesome.
*Culex (Culex) annulirostris Skuse, 1889.
Larvae were collected twice only. Early in August the species was found in clear water in a long-established road rut, in company with Anopheles p. moluccensis and Culex pullus. A 44-gallon drum filled with rain water yielded a few more larvae in the middle of September.
Imagines were occasionally collected in lighted huts during the evening.
Culex (Culex) sitiens Wiedemann, 1828.
Many larvae were taken from a fresh-water pool near the tidal limit of the Taut River, during October. No adult insects were encountered in the field.
Culex (Culex) fatigans Wiedemann, 1828.
This species was met with during August and September. On both occasions developmental stages were found in beached canoes containing rain water, at Manginuna village. Aëdes albolineatus and A. scutellaris shared the breeding place.
*Culex sp. nov.?
Early in September larvae were discovered in clear water in a wheel-rut, near the northern boundary of the Station. The distinctively-shaped siphon of this species—broadest at about a third distant from its base, with a uniform taper to the narrow tip—was obvious even on casual examination. These larvae had a marked white appearance. When disturbed, they sought shelter among debris at the sides and on the bottom of the pool, and remained perfectly still.
The same rut also contained developmental stages of Anopheles p. moluccensis and Culex pullus.
Several larvae pupated the day after collection. After a pupal stage lasting for two days, two male imagines emerged. Females were neither reared out nor encountered in the field.
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