Collection Of Resting Adult Mosquitoes At Kowanyama

J . Ausr. m t . Sol., 1983, 22: 19-24

19

COLLECTION OF RESTING ADULT MOSQUITOES AT KOWANYAMA, NORTHERN QUEENSLAND AND CHARLEVILLE, SOUTH-WESTERN QUEENSLAND B. H . KAY Quem~lanrllnsritute o/ Medical Re.rear1.h.Brumsron Terrace, Hersron. Qld 4006

Abstract A total of 85.639 adult female mosquitoes of 36 species were collected from daytime resting sites at Kowanyama (1974-76) and Charleville (1976-79). Most species rested outdoors but Cules yuinque/asciaru.r Say was abundant indoors. Most collections were made with a newly designed battery-powered aspirator. C u l e . ~annulirostris Skuse, Anopheles annu1ipe.r Walker and C.Y quinquejasriuius comprised 95-97?" of the mosquitoes collected. Resting boxes were attractive to C\ quinyuejuscia/us and An annulipes. At Kowanyama, Cu1e.i syuarnosus Giles predominated in collections from trees in the wet season. Resting catches did not correlate with bait collections, but reflected opportunistic behaviour being dependent o n availability of sites, proximity to breeding habitats and vertebrate blood sources during the previous night.

Introduction Our knowledge of the resting behaviour of Australian species of mosquitoes has come from piecemeal observations or larger studies at Townsville (O'Gower 1960), Murray Valley (Reeves et al. 1954; Lee et al. 1954; Myers 1956)or Papua New Guinea (Peters and Christian 1963). Marks (1972) summarised Australian data on rabbit burrows as harbourage for mosquitoes. This paper presents data from 2 additional localities which indicate that behaviour differs from locality to locality. Materials and methods Mosquitoes were collected from resting sites at Kowanyama in northern Queensland on 8 occasions from 1974-76 (see Kay 1979) and at Charleville in south-western Queensland on 6 visits between 1976-79 and as follows: 1976, February 6-22, 1977. January 25-April 7, 1978, February 5-March 9. October 17-25. 1979, March 6-22, December 11-19. The methods and equipment used were: Buttery-powered aspirutor.-An aspirator (Fig. I ) was constructed from a I m length of 100 mm (4 inches) PVC drain piping, a 12 v motor model H2600128 (Smith. England) drawing 37 watts, and 'Airotor' (Smith, England) fan I14 mm x 70 mm deep (4.5 x 2.75 inches) and a motor cycle battery of 9 amphour capacity. In use the battery was carried on the hip. The velocity of the air through the aperture was 5 m/sec.

Mosquitoes were collected between 0600-I000 h in light terylene bags, 25 cm long. attached by rubber bands to the front of the aspirator. In dry conditions, the mouth of the aspirator was used to disturb resting mosquitoes, and a stick in wet conditions. Collection bags were changed every 15 min to preserve the condition of the catch and minimise obstruction to air flow. The aspirator was used in a variety of habitats (Table 3 ) including the inside and outside ofhouses and natural niches. It was also used to clear the resting boxes. Rmrirrg ha.\e.s.-Resting boxes, similar to red boxes (Edman et a / . 1968) were constructed from brown cardboard cartons 33 x 27 Y 25 cm by folding and taping the top flaps into an ingress aperture. Boxes were

FIG.1-Battery-operated aspirator broken into pieces: top, PVC collection tube with handle; bottom from left, motor, fan and housing. battery in polyethylene carrying case and collection bag.

B. H . KAY

20

stacked in groups of 10-25 by placing the bottom row with apertures uppermost and then arranging boxes randomly on top which reduced the size of, but did not block the ingress apertures. They were emptied at 0900 h each morning. The catch from each cluster was one collection. In the dry season, moist cheesecloth was inserted in some boxes and in the wet season, boxes were sheltered from rain. They were placed in open sites shaded by houses from morning sunlight. Trec ,fogging.-At Kowanyama. trees 3- 15 m high, were fogged with 0.1% pyrethrins synergised with 0.6%piperonyl butoxide for 5 mins using a Swingfog SN 1 I high performance fog generator (Motan GmbH. Germany). Insecticidal fog rose through the canopy if the operator was within the canopy on a ladder or the generator had penetrated the outer foliage. The dense fog was propelled up to 10 m across the canopy, enveloping even the largest trees with relative ease.

From 0-15 min after spraying, mosquitoes were collected on clear plastic sheeting placed underneath. This was difficult to place correctly in winds greater than 8 kph. Collections were carried out between 1100-1500 h to allow moisture to dry off the leaves. One tree could be cleared in 45 min.

Results A total of 85,639 resting adult female mosquitoes of 36 species were collected, 56,068 from Charleville and 29,571 from Kowanyama. In addition 84,552 males were identified from Charleville, but those from Kowanyama were not sorted. Further details are contained in the Queensland Institute of Medical Research Annual Reports, 1975-77. At both localities, Cx annulirostris, Cx quinquejasciatus and An annulipes comprised 9597% of the total numbers of females (Tables 1-2). Cx quinquefasciatus was predominant at Kowanyama (89% of females) and Cx annulirostris (84%) at Charleville. At Kowanyama and Charleville respectively, blood engorged Cx annulirostris, Cx quinquejasciatus and An annulipes comprised 29 and 17,34 and 22,65 and 40% of females collected. The high engorgement rate for An annulipes is an overestimate due to difficulties in separating blood engorged from partially fed, unfed and half gravid females under field conditions. Their host-feeding patterns are being published separately (Kay et al. 1979; Kay et al. unpub. data). The wet season at Kowanyama is January-March and the dry July-October (Standfast and Barrow 1968). This classification also applies to Charleville (see Kay 1979).In Table 3 the collections of 36 species have been classified according to method, resting site and season. Particularly successful methods are represented by capital letters. Lower case letters indicate a mean catch of t o .1 per 15 min. or a relatively less TABLE1 NUMBERS O F RESTING ADULT MOSQUITOES COLLECTED AT KOWANYAMA 1974-76 No. females C.Yonnulirostris C.u quinquefhsciatus An annulipes Others

1108 26234 640 1589

TOTAL

29571

%

total 3.7 88.7 2.2 5.4

100

Blood fed No,

%

324 8925 413 381

29.2 34.0 64.5 24.0

10043

34.0

TABLE2 NUMBERS OF RESTING ADULT MOSQUITOES COLLECTED AT CHARLEVILLE 1976-79 No. males

An annulipes Others

71 573 7 518 3 516 1 945

TOTAL

84552

C.Yannulirostris

cx quinquejusciurus

%

total 84.6 8.9 4.2 2.3 100

No. females 46803 5 346 1975 1944 56068

%

total 83.5 9.5 3.5 3.5 100

Blood fed No.

%

8 150 1156 796 335

17.4 21.6 40.3 17.3

10 437

18.6

MOSQUITOES AT KOWANYAMA A N D CHARLEVILLE

21

TABLE 3 CLASSIFICATION*OF MOSQUITOES COLLECTED ACCORDlNG TO METHOD. RESTING SITE A N D SEASON Species

Kowanyama

Charleville

Anopheles bancroftii rtA. Gusif, wtd ra, gu, wd amictus (s.I.1 a, u. w, RtA, GUhSF, W T D RA, guHSifB, W D annulipes ra, u, wt farauti meraukensis a, gu. wt no wguinensis a , g, w Aedes alboscutellatu~ ta. UI, w australiensrs a, g. w rtA. gU, wt A, uh, wd notoscriptus a, us. w trrmulus a. g, w eidsvoldensis a, uh, w ta. gu, w normanensis a, u, w pseudonormanensis a , u, w tsigila.\a. uf, wd A, Uhi, Wd vit f iger sp. No. 71 (Marks undescribed) a, u, w bancrofiianus ra, u, wd Cules annulirosti is rA, gUHsitB, W D rtA. GUsif, WTD A, UH. W D austrolicus a. gus. wt bitaeniorhynchus RtA, GuhSIFb, WTD RA, UhSIFPB, W D yuinquefasciatus a , u, w syuamosus TA. Gus, Wd a , u, w rta, G , Wd starckeae vicinus t, w rTA, GUe, Wtd Cules pullus cylindricus A, Uh. W RA, gUsifE, Wtd (Lop.) spp. hal(ia.\ii t, w Mimomyia rlegans a, u, wd Coyuillertidia santhogaster a, u, w Mansoniu septrmpunctatu a. g, w rA. Gus. wTd unijormis Tripteroides punctolateralis a, us, w Uranotaenia albescens rtA. gUhsE, Wtd lateralis ra, gu, w nivipes ra. gu. w _____ _ _ ~ * Abbreviations as follows: Capitals signiiy relative applicability-resting boxes ( R or r), tree fogging (Tor t) etc.. battery-powered aspirator (A) on/in gauze screens (G), undergrowth and litter (U), tree trunks, stumps, holes (H), sheds, outhouses, washhouses (S), indoors (I), fowl coops (F),drains and traps (P), water hyacinth (E),burrows (B), wet season (W), transitional (T) and dry season (D). ,

successful method. However, because overall abundance influenced the mean catch, rare or uncommon species (see Kay 1979) were recorded in lower case regardless of method. Cx squamosus is therefore interpreted as follows: Kowanyama; tree fogging and aspirators, especially on gauze insect screens, in the wet season; Charleville, low numbers collected in the wet season using an aspirator in undergrowth. Species collected Cx annulirostris was difficult to find resting at Kowanyama (1.1 per 15 min. collection) in contrast to Charleville (41.3) (Table 5) although comparable outdoor sites were examined at both places. Trees were examined as an alternative resting place but with minimal success (0.4) (Table 4). At Kowanyama, Cx annulirostris was found resting on gauze insect screening especially in the dry season (1 .O-7.0)compared to wet and transitional season catches (0.8-1.2). At Charleville, Cx annulirostris was collected from a variety of shaded ground cover especially Paddy's lucerne, Sida rhombqolia Poison Pratia, Pratia concolor and Buffel grass Cenchrus d i a r i s in 1977, and in 1978 in ground cover and flood debris suspended in Paperbark trees, Melaleuca linearizfolia along the Warrego River; in 1979 similar debris was unproductive but overgrown couch grass harboured record

B. H. KAY

22

numbers. Cx annulirostris occurred in rabbit burrows together with An annulipes and Cx quinquejasciatus. Largest numbers of Cx quinquejusciatus were collected resting indoors in houses, sheds, toilets and chicken coops or outdoors in resting boxes, drums, gully traps or in other man-made niches. An annulipes was collected mainly from tree trunks, tree holes, rabbit burrows, under bridges and indoors. At Kowanyama, An bancrofiii Giles rested both outdoors (0.2) and indoors (1.5) (Table 5) but was most frequently aspirated off insect screens outdoors. Cx squamosus was the predominant species fogged from the tree canopy (1.4) (Table 4). TABLE 4 MEAN CATCH OF MAJOR SPECIES OF RESTING FEMALE MOSOUITOES ACCORDING TO METHOD Kowanyama

_____

Species C.Yunnuirrostris

C s yuinqu
Other species

Aspirator

Resting boxes

1.6(4.5)* 30.2(87.1) 0.8(2.3) 0.6( 1.6) 0.2(0.6) (3.9)

0.4( 1.4) 24.9(95.6) 0.5(1.9) t o . l(O.1) O(0)

TOTAL 21 591 NUMBER OF COLLECTIONS 613 MEANCATCH 35.2

(1.0)

Charleville

Tree fogging

Aspirator

Resting boxes

0.4( 15.3) 0.4(15.3) <0.1( 1.6) 1.4(55.2) < 0.1(2.2) (10.4)

40.3(86.4) 4.6(9.7) 1.7(3.6)

OW) 3.6(87.8) 0.5( 12.2)

183 70 2.6

55 961 1 152 48.6

7797 296 26.3

-

~

~

(0.3)

107 26 4. I

* Percentage of total catch in parenthesis. 5 TABLE MEAN CATCH OF MAJOR SPECIES OF RESTING FEMALE MOSQUITOES ACCORDING TO SITE

Kowanyama

Species Outdoors C.Yu n n u l i r ~ , ~ ~ r i , ~ C.1 quinyurjusciutus

An unnulipes C.\ .ryuumosus An huncrojtii Other species

TOTAL NUMBER OF COLLECTIONS MEAKCATCH

Fowlyard

Outdoors

Indoors

1.1(3.9)* 2.0(4.5) lS(1.31 25.5(88.2) 40.0(89.9) I lO(97.5) 0 0.7(2.3) 0.4(0.4) 0.4(1.2) 0 0.7(0.6) 0.2(0.6) 1.5(3.4) O.l(O.1) (2.8) (2.2) (0.1)

41.3(84.7) 4.2(8.5) 1.6(3.3) 0

1.8t13.9) 14.3(11.5) 7.2(54.1) 108.3(87.6) 3.6(26.9) l.O(O.8) 0 0

27 789 962 28.9

Indoors

Charleville

89 2 44.5

1693 15

112.9

~

-

~

(3.5) 55113 I 131 48.7

Fowlyard

(5.1)

584 44 13.3

(0.1) 31 3 123.7

* Percentage of total catch in parenthesis

Resting collec~tionsas an indicator qf seasonal abundance The log (x 1 ) mean monthly catch per 15 min for female Cx annulirostris, Cx quinquejasciatus and An annulipes collected resting on all trips to Kowanyama, except May 1975, were correlated with human bait and dog-baited stable trap collections using data from Kay (1978, Tables 3.3, 3.4 and 3.6) and Kay (1979, Table 3). All the correlation coefficients were non-significant (P > 0.05).

+

Discussion The battery-powered aspirator has proved both efficient and durable. I t closely resembles the portable suction apparatus used by Davis and Could (1973) but is simpler, omitting an enlarged holding cage. Insect condition was preserved by regular bag changes. Air flow was improved by replacing the solid vented fan housing with expended metal mesh. This reduced the weight and doubled the linear airflow from 2.4 to 5 misec.

MOSQUITOES AT KOWANYAMA A N D CHARLEVlLLE

23

The resting boxes attracted large numbers of C.x-~ u i n ~ u ~ ~ ~ and ~ s eworked i a ~ u best s when placed in nests of 10-25. Unlike the red boxes of Edman et a/. (1968) used extensively in the United States, the interiors of these were light brown. Tree fogging revealed a concentration of Cx squarnosus in trees. Similar methods have been used for collecting arboreal insects in cocoa plantations in Ghana (Gibbs and Leston 1970) and arboreal Orthoptera in Costa Rica (Roberts 1973). The size of the mosquito collections using the battery-powered aspirator depends on recognition of suitable resting sites, effort expended by the collector, the state of charge of the battery as well as numbers of mosquitoes present. The distribution of all species was patchy and the productivity of resting sites varied from trip to trip, probably according to the various niches available, the distribution of hosts during the previous nights and overall proximity to breeding sites. At Kowanyama, greatest numbers of Cx annulirostris were aspirated outside from insect screens on the shaded side of houses during the dry season when population numbers and choice of resting sites were reduced. Although at Charleville screens were relatively unproductive, Cx annulirostris could be collected from almost any shaded, moderately dense herbage but their density varied markedly. The most productive collections at Kowanyama were a series of 7 along the bank of Magnificent Creek totalling 1205 with a mean C.u annulirostris catch o f 10.2 (Standfast et ul. 1968). Subsequent collections at this site by Standfast (pers. comm.) and in the present study were unsuccessful. The different distributions of resting Cx annulirostris at Charleville and Kowanyama is attributable to the habitats at Charleville being fewer and more easily definable. In the wet season at Kowanyama, monsoonal rainfall produced extensive harbourage among new growth. At Albury, southern New South Wales C.\ annulirostris rested in ground vegetation, mainly Polygonurn sp. but at Urana, N.S.W. where ground cover was sparse, Cs annulirostris rested in trees (Myers 1956). At Kowanyama, t&e mango canopies appeared to provide ideal shelter for C.\ annulirostris, but mosquitoes were only collected from them during the wet season. In the dry season, the scarcity of such harbourage should have increased their attractiveness, despite lower mosquito numbers. Detinova (1962) has pointed out that certain physiological age grades may be poorly represented in resting collections. Because of the physical difficulties in sampling extensive areas, resting collections produce more limited data than d o methods which sample an actively-flying population drawn from a wide area by wind, light or odour. These considerations may explain the discrepancy between resting and animal-baited methods as indicators of seasonal abundance at Kowanyama. As bloodfeeding is fundamental to the transmission of pathogens, these data would suggest that resting adult collections are inappropriate for vector surveillance. Acknowledgements

I am most grateful to Mr Ian Fanning and the numerous people that assisted with collections at Kowanyama and at Charleville; to Professor R. L. Doherty, formerly Director, QIMR, D r E. N . Marks QIMR and Professor D. S. Kettle, my Ph. D. supervisor, Department of Entomology, University of Queensland for manuscript review; to Mr P. Cusack, Department of Mechanical Engineering, University of Queensland for assistance in design of the battery-powered aspirator. This study was funded by the Queensland State Government and the National Health and Medical Research Council, Canberra. References DAVIS. E. W. and Gouru. D. J. [ 19731.-- A portable suction apparatus for collecting mosquitoes. Mosyuiro N P M X3 3 246-247. D E I I N O \ AT. . S. (1962).-Age grouping methods in Diptera of medical importance. Monogruplr Srr. 1V.H.O.No. 41. Geneva. ED MA^. J. D., EVANS.F. D. S. and WILLIAMS. .I A . (1968).-~--Development of a diurnal resting box to collect Culiseta melanura (Coq.). Amer. J . Trop. Hyg. 17: 451-456.

24

B. H . KAY

GIBBS,D. G. and LESTON, D. (1970).-Insect phenology in a forest cocoa-farm locality in West Africa. J. uppl. Ecol. 7: 519-548. KAY.B. H. (1978).-Aspects of the vector potential of Cule.\ urmulirostris Skuse 1889 and other mosquitoes (Diptera: C-ulicidae) in Queensland, with particular reference to arbovirus transmission at Kowanyama and Charleville. Ph. D . thesis. University of Queensland: Brisbane. KAY.B. H. (1979).-Seasonal abundance of Cules annulirosrris and other mosquitoes at Kowanyama, north Queensland, and Charleville. south west Queensland. Au.rr. J. e.vp. B i d . Med. Sci. 57: 497-508. G . M . (1979).-Host preferences and feeding patterns of KAY.B. H., BOREHAM. P. F. L. and WILLIAMS, mosquitoes (Diptera: Culicidae) at Kowanyama, Cape York peninsula, northern Queensland. Bull. ent. Res. 69 441-457. K. J. and O’GOWER.A. K. (1954).-The blood sources of some Australian mosquitoes. LEE,D. J., CLINTOK. Aust. J . hid. Sci. 7: 282-301. MARKS,E. N . (1972).-Mosquitoes (Culicidae) in the changing Australian environment. Q d Nut. 2 0 101116. MYERS,K. ( 1956).---Methods of sampling winged insects feeding on the rabbit 0ryctoIugu.s i.uniculus (L). CSIRO Wildl. Res. 11: 45-58. O’GOWER,A. K. (1960).-Townsville culicines as possible vectors of dengue and allied viruses among local feral fauna. Aust. J. exp. B i d . med. Sci. 38: 1-9. S. H. (1963).-The bionomics, ecology and distribution of some mosquitoes PETERS.W. and CHRISTIAN, (Diptera. culicidae) in the territory of Papua New Guinea. Ac,/u Trop. 2 0 35-79. W. C., FREXCH. E. L..MARKS.E. N . and KEKT,N . E. (1954).-MurrayValleyencephalitis: A survey REEVES. of suspected mosquito vectors. Amer. J . trop. Med. Hyg. 3 147-159. H. R . (1973).-Arboreal Orthoptera in the rain forests of Costa Rica collected with insecticide: A ROBERTS, report on the grasshoppers (Acrididae), including new species. Proc. Acad. Nut. Sci. Philud. 1 2 5 49-66. STANDFAST, H. A. and BARROW,G. J. (1968).-Studies o n the epidemiology of arthropod-borne virus infections at Mitchell River Mission, Cape York Peninsula, north Queensland I. Mosquito collections, 1963-1966. Truns. R. Soc.. trop. Med. Hyg. 6 2 418-429. 1. D., KAY,B. H. and Symons, M . H. (1968.STANDFAST, H. A,, DOMROW,R., WELCH,J. S. FANNING, Entomological and field aspects of arbovirus field programme. Mitchell River. Rep. Q d Inst. med. Res. 2 3 6 . (Munuscript received 2i Seprernber 1981. Revised 7 Februurj 1982.1