new zealand's northern mosquito survey, 1988-891

13 Pages·2004·5.46 MB·English

JUNE 1990 Nsw ZnnLeNoM osQUIToS unvnY 287
NEW ZEALAND'S NORTHERN MOSQUITO SURVEY, 1988-891
MARSHALL LAIRD,
"Awawhare,"P ahi Road,R D #1, Paparoa,N ew Zealan'd
ABSTRACT. The latest mosquito survey of the warmer regions of Nerp Zealand (NZ) sampled 2'304
Iarval mosquito habitats of all major categ"oriesW. hile revealing_noe videnceo f new establishmentso f
""lo""tii.J U"- ".ii"""iiuoae"sd, noiiw p orro idnu tcheed f iumtuproer t(aenstp"deactiaa llryei fvtehael in''gg rtheee nuhnoduesreue ,fifleizcat"ti oenve onft utyaplleys c aouf sheasbe ivtaetns q tuhiatet
small rises in averaget emperaturesa nd seal evels). Although Iong feared additions of malaria vectors to
u fur.ru still lacking"anys pecieso fAn opheleso, r of essentiallyt ropical arbovirusv ectors from neighboring
;;;;i". a" the n6rth and northeasti may not materialize failing climatic amelioration, a new danger
upp""t"d at the beginning of the 1988-89N orthern Mosquito Surviy whel A ed'esa lbopictusw as.r eported
for the nrst time fiom Fijii. This vector of dengueh emorihagic fever and Ross River virus has since been
.pi""Ji.g *iaay on the Lrchipelago's main iJland, Viti Levu, whence much air and sea traffic reaches
iiZ. i"foi-ution presenteda ni diicussed herein strongly supports the continuance and improvement of
international aircraft disinsection and other insect quarantine measures.
INTRODUCTION in colonizing NZ, where there are North Island
east coast and northern South Island port foci
On the basiso f his 1918-19N orth Auckland (Belkin 1968)-exhibits a dispersapl attern fullv
mosquito survey, Miller (1920) reported 2 of supportingt he statement (Lee et al. 1982):" It
New Zealand's( NZ's) 3 exotic speciesb elieved s"u*s .eu.ottable to assumet hat Ae. notoscrip-
to have been established since the European tus has been introduced to New Zealand."
rediscovery.T hese were Culex quinquefoscintus New Zealand'st hird and latest presumed ex-
Say [isted as Taeniorhynchusa cer (Walker) see otic is Ae. australis( Erichson).I ts synonomyi s
Lee et al. (1989)1, and Aedes notosviptus fully discussedb y Lee et al. (1984),w ho accept
(Skuse)[ reporteda sa membero f subgenusO ch- its (Belkin 1962)s ubgenericd esignationa s one
lerotatus-see Lee et al. (1982)1.T he latter, of 2 otherwise uniquely Australian members of
actually a Finlnya, is otherwise found from In- the subgenusH alaedes.O nly known from south-
donesiat hrough Papua New Guinea to Australia ernmostp rovinceso f the SouthI slanda nd Stew-
and the New Caledonian area. A Category 8 art Island (Nye 1962,N ye and McGregor 1964,
Iarval habitat3 utilizer in nature, it readily dis- Belkin 1968),t his brackish water, rock pool-
perses to Category 9 sites, as do many other utilizer may well be a Tasmanian strain im-
members of its subgenus( Horsfall 1955, Laird ported by timber vesselst o southern NZ ports
1988).T his behavioralt rait renderedA e. noto- by the 1960s (Pillai and Ramalingam 1984)'
scriptus as transportable aboard sailing vessels These authors disagreedw ith Belkin's (1968)
as the now virtually pantropical (and to a large soeculationa bout a natural (windborne caniage
extent pansubtropical, bearing in mind their oleggs) arrival from Australia, and I agreew ith
American dispersal) Cx. quinquefasciatus and them. In southern parts of the South Island, Ae.
Aedesa egypti( Linn.). Despitet he view of Chris- australiso ccupiesC ategory 6 and 8 larval habi-
tophers (1960) that the Iatter could establish tats of brackish splashpoola nd seepagety pes,
northward from just south of Auckland City "similar to those occupiedb y O. fusctts" (Belkin
where the 10"C winter isotherm line coincides 1968).A s yet, the former is unrecordedf rom the
with the Bombay Hills, northern NZ may still North Island, and need not concern us further
be a shadet oo cool for the latter speciesN. ot- here.
withstanding,A e. notoscnptus-having proved Miller (1920)a nd Graham (1929,1 939) rec-
rather more successfutlh an Cx. quinquefasciatus ognized the danger posed to NZ by possible
introductions of Anopheless pp. to a temperate
country lacking malaria and its vectors. The
"Anophe-
1 This researchw as conductedf or the New Zealand latter author (1939) actually reported
Department of Health, which has approveda nd partly les maculipennisM eigen" from vesselsr eaching
supportedp ublication. Auckland from Indonesia in May and Septem-
2 Honorary ResearchF ellow, Department of Zool- ber 1929.A s shownb y Belkin (1962)a nd Lee et
ogy, University of Auckland, Private Bag, Auckland, al. (1987b),t his identification of a continental
Ne3wL aZrevaalla mndo.squito habitat classification herein fol- European/SW Asian/northern Siberian mos-
quito must have been wrong. Perhaps Graham
Iows the rational l1-category system (Table 3) pro-
posed as an international standard by Laird (1988). was misled by one of the few sourceb ooks that
Some New Zealand.e xamples of these categoriesa re would then have been available to him, i.e',
illustratedi n Figs.1 -12. Tidswell (1910),w hich referst o An. maculipen-

Jounuu oF THEA uenrcnNM oseurro CoNrRorA, ssocrlrrou Vor,.6 , No. 2
Auckland,i n the first weeko f April, 1989.T here Interestingly, all 3 of the abovee pibionts were
and elsewhereu nder similarly heavily polluted present on the cuticle ofthe largest-stageI arvae
circumstances,t he sheathedb acterium, Sphaer- of one of Belkin's NZ "Culicidae," Paradixa
otilus natans Kutzing (see Laird 1959, 1988) neozelandic(aT onnoir), collectedf rom a highly
added to the larval vestiture together with uni- polluted stream (Category1 ) in South Auckland
dentified Cyanobacteriaa nd Fungi. (late November). The site was not far from the
Mangere SewageT reatment Plant, from which
Belkin (1968)r eported both larvae and adults
Table 1. Regional coverage of survey. in early March 1965.A lmost 2 decadese arlier,
in the immediate aftermath of World War II
Region Samples
and in my then capacity of Royal New Zealand
Northland Area Health Board 853 Air Force Entomologist, I made an urgent flight
South AucklandH DU 599 from Wellington to Auckland to investigate a
Hamilton HDU 513
report from an airman who had served in the
AucklandC entral HDU 183
TakapunaH DU 156 South Pacific forward zone. Having learnt to
recognizea nopheline larvae on Guadalcanal,
Total 2,304 Solomon Islands, and in Papua New Guinea, he
had noticed what he took to be these in the
surroundingso f NZ's then only international
Table 2. Mosquito species identified. airport. Upon arrival, they turned out to be the
surface-hauntingI arvae of P. neozelandicaT. he
Species Coliections incident servesa s a fine example of what would
* Culexp eruigilzns Bergroth 931 nowadaysb e termed "community participation"
** Aedesn otoscriptus( Skuse) 426 and good public relations in vector awareness
** Culex quinquefasciatusS ay 156 and control.
*
** MOCuaploieferri xgaf ousetseLclduiaisaeaH B rugetyltkroionnp us( Walker) 3222 noItno svcieriwpt oufs twhieth f reCqru. epnecryuo ifg ailsasnosc aiantdio/onot fACex..
quinquefasciatus( Table 4), it is of interest that
larvae of the first-mentioned speciesn ever bore
Total 1,549***
Vorticella nor Epistylis.T his might be supposed
*
**I ndigenous. due to the fact that such associations were
Exotic.
*** mostly in the relatively clean water of Category
This total exceeds the number of mosquito-
9 Iarval habitats. However, although V. micros-
positive larval habitats reported (1,333, Table 3) be-
cause many of the latter exhibited mixed-species in- toma and E. lacustris populations peak under
festations (Table 4). polysaprobic and mesosaprobicc onditions re-
Table 3. The 11 major categories of larval mosquito habitats, showing their utilization by Culicidae in the
1988-89 Northern Mosouito Survev.
Number Number
Total no. larva- Percentage larva- Percentage
Categories samples positive positive negative negative
Aboue-grounwd aters
1. (Flowings treams-Fig. 1) 85 32 38 53 62
2. (Pondeds treams-Fig. 2) r72 97 56 44
3. (Lake edges-Fig. 3) ri) 6 4 6 7 54
4. (Marshes-Fig. 4; and oa 47 48 50 52
swamps-Fig.5)
5. (Shallowp ermanentp onds) 89 38 43 DI
6. (Shallowt emporaryp ools) lt4 75 66 39 34
7. (Intermittent ephemeralp ud- 84 68
zl Dz
dles)
8. (Natural containers-Figs.6 , 155 46 30 109 70
7)
9. (Artificial containers-Figs.8 - r,493 963 65 530 35
10)
Subterraneanw aters
10. (Natural) I I 100 0
11. (Artificial-Figs. 11, 12) 1 I 100 0
Totals 2,304 1,333 58 971 42
JUNE1 990 Npw Zpnlnrp MosQutro SuRvnv 293
Table 4. Mixed species infestations of individual larval habitats (species listed in decreasing order of
associations, read irom left to right; figures below each taxon show the number of sites involved in each
association).
Aedes Culex Culex CuLex Opifex Maorigoeldia Total
notoscriptus peruigilans quinquefasciatus asteliae fuscus drgyroptls assocratrons
t42 t42 t42
a9 32
5 5 5 5
1 1 1
I 1
JO ; JO
1 1 I
Overall 181 183 I 277
totals
spectively (Laird 1988), both can lgtgttF l?f peruigilans in an atypical Category- 2- slte
less organic enrichment; and as Bick (1972) iponded stream) which was spring-fedi n the
states with respect to the former, "Small "- io- immediate vicinity of severaln ormal Opifexlar
nies may occui under mesosaprobicc onditions, val habitats at Mangonui, Northland.
solitary specimense ven being found in the oli- Turning to parasitesa nd pathogens,w ith just
sosaprobicz one"'While as already mentioned 2 exceptions these were conspicuousb y their
i-.trt ou.. half of the double infestations encoun- absence.I n the light of wide field experience
iered occuned in tires, most of which were so elsewherei n the world, it was particularly sur-
positioned as to be charged with rainwater ini- prising to find no trace of mermithid nematodes,
ii"Uy, .o-. other Category 9 larval habitats in micro-poridian Protista or Blastocladiidea of
which ae. notoscriptusw as associatedw ith one the genusC oelomomycesin, so large a sampleo f
or both of the 2 species of Culex held foul material-the more so, as J. S' Pillai and his
water-for example, meat cans that still bore colleaguesh ave describedm icrosporidians from
traces of their original contents when thrown Maorigoeldia argyropus and the apparently in-
into open garbaged umps. One such can exhib- troduced Ae. australis,b esidesC oelomomyceisn
ited Cx. peruigilans larvae, all with a heavy ves- the latter and Op. fuscus,i n the South Island.
titure of V. microstorno, together with many Ovoidal bodies plentiful throughout the hem-
perfectly clean larval Ae. notoscriptus-T.h e latter ocoelo f all Op. fuscuslate-instarl arvae collected
speciesw as similarly free from epibionts in a from a brackish rockpool in Te Karo Bay, east-
horse trough organically rich enough to have ern Coromandel Peninsula, on April 7, 1989,
attracted Cx. quinquefasciatuss imilarly heavily appeareda t first sight to be resting sporangiao f
infested with V. mi.crostomaA- gain, in a plastic a- ipecies of CoelomomycesM. ore detailed ex-
bucket containing quite clean water, there was amination in collaboration with J. S' Pillai sug-
a scattering of Epistytis over the cuticle of Cr. gests that the organism is really a eugregarine
p'Aee r.u igilanslarvaei n associationw ith uninfested protozoan.
iotoscripifus, while a similar situation in- Finally, fungal hyphae and conidiophores-as
volving either E. lacustriso r V. mi'crostonlawas yet unidentified-were noted on the thorax and
noted for a numbero ftires. anal segmento f larvae from 2 Category t habi-
Perhaps,j ust as most cladoceranss uffer far tats. The speciesc oncernedw ereA e. notoscrip-
lessf rom epibionts than do copepods( duet o the tus (Orua Bay, South Auckland, November 21,
former's hydrofuge qualities as opposedt o the 1988-in water tank), and Cr. pervigilans,i n
latter's hydrophilic ones?-Hutchinson, 1975), association with uninfected Ae. notoscripttts
similar physical phenomena may apply within (Point ChevalierA, uckland,D ecember5 , 1988-
the Culicidae. Although the matter merits ex- in tire).
perimental study, the environmental prefer-
ences of Op. fuscttss uffice to account for the DISCUSSION
general freedom of larvae of this speciesf rom
ciliate epibionts. For while it proved free from Occurrence and preualcnce of Culicidae in
such infestation in 31 ofthe 32 sites from which northern NZ: The 4 native and 2 (long since)
it was identified, these were as usual decidedly accidentally imported species recorded tallied
brackish, a circumstance inimical to V. micros- with earlier findings, apart from minor details
torna andE .lacustris, both of which were equally of distribution and incidence. The latter could
scatteredo ver larvae of Opifex and those of Cr. reflect seasonavl ariables( e.g.,s ummerr ainfall
JouRNer,o F THE AuenrclN Mosqurro CoNrnor, Assocra,rroN VoL.6,N o.2
vs. drought) and survey coverage;t he project farming districts. It has been aided in its disper-
took place in rather a wet period offering opti- sal by the practice of piling many discardedt ires
mum larval habitat availability, but had it been (sometimesu p to 100 or more) to weigh down
conducted a year later a sustained summer the plasticc overso f rural ensilagep iles,t o men-
drought would have resulted in a substantiallv tion only one exampleo f the diversity of Cate-
reducedt otal of collections.A nd until recentlv. gory 9 larval habitats characteristic of today's
I would have acceptedt he opinions of Belkin throwaway society. Via artificial containers Ae.
(1968) and Pillai (1979a)o n the comparative notoscriptus had already radiated into other
rarity and low frequencyo f Cx. quinquefasciatus, types of NZ larval habitats characteristic of
which accordingt o the former author is "largely those of its countrieso f origin [i.e., such Cate-
confined to coastal areas in the vicinity of the gory 8 sitesa s tree holesa nd rock potholes( Lee
largerp orts on North Island."T his is indeeds o. et al. 1982)1,l ong ago. Thus Graham (1929)
but i"t gwuallsy not until early April that attention to reported it from rock hollows, "especially those
the traps" of the stormwater drainage occurringi n caves"( i.e.,C ategory1 0) as well as
system of Parnell, Auckland City, revealed a from rot-holes in various specieso f native trees,
great abundance of this speciest here. As the the leaf axils of nikau palms and Astelia spp.,
barredc overso f theses umpsw erer aisedo ne bv and exceptionallye ven from "drains, swamps
one from the gutters, huge assemblageso f aduli and water-holes."I n the present survey it was
and larval Cx. quinquefasciatuso, ften in associ- commonlyc ollectedf rom the leaf-baseta nks of
ation with Cx.p eruigilans and occasionallyw ith neotropical Bromeliaceae (Fig. 7) grown as
Ae. notoscriptusw ere revealed beneath, amply greenhouseo rnamentals. An interesting North-
accounting for many complaints of a serious land finding concernedW aipoua Forest, where
biting problem from local residents.I n the final a marginal zone investigatedi n late March 1989
days of the survey, a similar situation was re- yielded several Category 9 sites ranging from a
vealedi n parts of South Auckland,w here, ,gully "gully trap" at a camp mess hall, through steel
traps" neart he airport'sI nternationalT erminal drums, tires, bucketsa nd ubiquitousb eer cans
at Mangere were sustaining large populations of and bottles, to many Category8 (natural con-
both Cr. quinquefasciartusa nd Cx. peruigilans tainers) ones. The former group had opened
and thereby furnishing sourceso f both to air- entry to the latter, in which Ae. notoscriptnsw as
craft departing for foreign destinations, and at identified from slits in prostrate logs and stand-
the samet ime serving as potential oviposition ing trees, as well as from Bush FIax. Astelia
sites for pollution-tolerant foreign mosquitoes neruosal,e af axils. In this center of concentra-
shouldt hesee vadeo n-arrival disinsection. tion of an exotic peridomesticm osquitor evert-
Still on the matter of international arrival/ ing to its original natural larval sites,A e. notos-
departurep laces,o ther Cx.q uinquefascialucso l- criptus larvae were not only also found in a
lections were made from a variety of Category9 Category 2 habitat (ponded stream), but in a
sites on Auckland's container wharf and the streamb ackwater( Category1 ), too.
Devonport Naval Base. Positive samplesw ere No intensive samplingo f leaf axil, tree hole
also taken on the nearby Hauraki Gulf islands and other Category 8 habitats was undertaken
of Waihekea nd Rakino.F urther afield,B elkin's in densef orest.H ad this beend one,t here would
(1968)f irst record of this speciesf rom the old certainly have been many more recordso f the
port of Coromandelw as confirmed.N ew Coro- indigenous Cx. asteliae and Mg. argyropus;b ut
mandel Peninsula locality recordsw ere obtained it was felt more important for the purposes of
a little further north, at Koputauaki Bay, and the survey to concentrate on the surroundings
from the old port city of Thames (in the latter of airports and seaportsa nd the rural hinterland
casef rom a Category t habitat, backwaters of a that further mosquito arrivals would have to
foul streamlet). Perhaps the most interesting traverseb efore reachingm ajor forests.C oastal
new finding of Cx. quinquefasciatusw as the first areasw ere searchedw hereverf easible,t hough,
inland one,f rom a schools wimmingp ool in the and this resulted in findings of Op.f tncus whet-
city of Hamilton, Waikato. The speciesw as not ever suitable Iarval habitats existed.
collected elsewheret here, and the finding could The only other mosquitoesk nown to occur in
easily have been due to road, rail or air trans- the northern parts ofAuckland Province but not
portation from Auckland; in which connection, reported in the 1988-89 larval survey are: Ae.
it is pertinent that an unusual Category9 larval antipodeus( Edwards), Coquillettidia tenuipalpis
habitat, a pool on the metal floor of a railway (Edwards) and Cq. iracunda (Walker). Like
wagono n an Auckland siding,y ielded Cx. per- other memberso f the tribe Mansoniini, Coquil-
uigilansa nd Ae. notoscriptus. Lettidias pp.h ave larvaew hich "rely on air within
The last-mentioned exotic, now North Auck- the underwater roots of emergentp lants and all
land's second most plentiful and widespread have the siphon highly modified for piercing
mosquito, has spread inland throughout the plant tissue" (Wood et al. 1979).L arvae of nei-
I
JUNE 1990 Nrw Zser,eNoM osqurro SuRvev 295
ther of the NZ speciesa re known from the field, 20% and 427a, rcspectively.A s 46% of aIl Cx.
althougha ccordingt o Belkin (1968)1 st instars quinquefasciatfussa mplesw ere mixed ones, too,
were obtained from eggr afts by L' J. Dumbleton [h... figut.t are evidenceo f the successo f both
(unpublished).A dults have been obtained from exoticsi n competingf or availablel arval habitats
Northland since the pioneer survey of Miller in the NZ environment'
(1920:a nd seeB elkin 1968),t hereb einga strong A generalu nderutilization of potential larval
association with marshlands rich in sedges, -o.quito sites in northern NZ has thus been
reeds and other aquatic vegetation. Typical NZ turned to account by both exotic immigrants,
Raupo (a bullrush, Typha orientalis) and Carex although distinctly more so by Ae. notoscriptus
spp. are central to the aquatic complex within than 6y Cx. peruigilaias. The former, having
*tiictr UottrN Z specieso f Coquillettidiom ight be adaptedb ettei to local conditions' has radiated
expected to be found. So far, the manual up- into varied and widely dispersed larval niches
rooting of much such vegetation, with care to (both near the likely ports of entry and deep
divertlhe underwater parts into a submerged inland) to become the region's most plen"tIihfuisl
drum without breaking the water-film and so culicid after the indigenousC x.p erui.gilans.
dislodging larvae, has proved fruitless. highly adaptable speciesw as obviously largely
Aedbs antipodeusi s a winter floodwater uti- frJe irom mosquito competition prior to the
lizer, larvae of which were collected in 6 of arrival ofthe 2 foreigns peciesI.t has a remark-
Pillai's (19?94)J uly-September 1978 samples ably wide range of tolerancesi n oviposition site
from the vicinity of Whangarei. Although the selection,h aving been collected from all 11 lar-
femalesa re activey ear-round( Belkin 1968),t he val habitat categories( positive exampleso f 6 of
timing of the present survey would have made which are illusfrated in Figs. 1-5, 8-12), and
it rather unlikely to come across immature dominatingi n all but one of them (Category8 )
stagest,h e more so as populationso f this,mem- in Table 5.
beiof the subgenusO chlerotatuss eem charac- While natural containers were the only larval
teristicallys mall. habitats where Cr. peruigilans was subordinate
Factors releuant to possiblef uture establish- to other species,o ne ofthese was C*. asteliae,a
tmemenptes roaft efo crelimigna tme oasnqdu iatone sai nd eNqZua: tOe rfafenrgineg oaf d"tehraitv aatsivteJloiafte hw ea fso fromrmere.Bd efrlokmin (a1 f9o6u8n)ds uerg pgoepsute-d
environments for Culicidae, NZ nevertheless lation of the peruigilans stock on an isolated
still has an unusually limited mosquito fauna volcanic island where the only available fresh
(14 species,o nly 11 of them indige-nous)f or a water was in astelia axils" (probably those of the
counfty of 269,063k m'(cid:0) (103,886m i.'(cid:0)). It is thus Perching Lily, Collospermumh astatu,rL a con-
pertinent to consider how this may affect the spicuouse piphyte on forest trees which is also a
question of vulnerability to new introductions piott"er on bare volcanic rock). Such axils and
of pestsa nd vectorsp arallelingt hoseo f arthro- lorest tree holes are commonly negative for na-
pods of agricultural and forestry importance tive mosquitoes,a nd although Ae. notoscriptus
that continue to take place despite quarantine was quick to take advantageo fthe circumstance
measuresa s expandingt rade and tourism break and was the speciesm ost often collected from
down former isolation. Category8 habitats-being present in 18 (397o)
The proportion of 1988-89 collecting sites of the 46 found positive-the proportion of such
actually positive for larval mosquitoes (58%; habitats that proved negative (70%; Table 3)
Table 3) was appreciably Iess than has been was the highest for all categories. Originally
found characteristico f NZ's nearera nd warmer clearly a utilizer of surface and cave waters
neighbors. Thus widespread surveys in many
tropical South Pacific island groupsa nd Queens- Table 5. Culex peruigilans occurrences (percenlages
land, Australia (Laird 1956a), revealed that derived from overalllarva-positive habitat figures in
overall, 372 (817o)o f 457 actual and potential Table 3).
larval mosquito habitats sampled exhibited lar- Category Collection(s) % of occurrence
vae.M oreover,L 3l (3\Vo)-by comparisonw ith 1 3 0 94
217 (16%) in the present project-harbored o 0 9 95
more than one culicid species.T hus 85 (25%) 3 5 83
held2 specie,s3 3 (9%)3 ,9 (2%\4 , 3 ([Vo\5 and 4 4 4 94
| (<l%\ 6. As alreadyi ndicated,t here were no 95
b J o
multiple infestations beyond 3 in this Northern 6 7 3 97
Mosquito Survey, all but 5 of them involving 7 2 6 96
only 2 species( Table4 ). Furthermore,w hile Cr. 8 3 7
peruigilans and Ae. notoscriptush eadedt he list 9 620 64
for mixed infestations in almost equal numbers 10 1 100
11 1 100
(Table 4), the species-proportionso f each were
296 JounNu, oF rHE AnrnRrceNM osqurro CoNrnor,A ssocrnrrox VoL.6,N o.2
(Categories1 -7, 10), Cx. peruigilansm ust have these are well-suited to keeping stock troughs
begun to have accesst o artificial containers in relatively or totally free from larvae (their effr-
pre-European times. For the Moriori made cacy of courseb eing subject to the frequency of
water containets, hahana, of wood and perhaps emptying for cleaning). There is presumptive
of pumice also (Skinner 1923),a nd the Maori evidenceh eret hat the phenomenao f notonectid
manufactured both types while their beached flightlessnessa nd environmentally determined
dugoutc anoesw ould have affordeds imilar larval polymorphism (Young 1970) might have some
habitat prospects to mosquitoes as those of practical value in limiting mosquito populations
many tropical Pacific islanders still do today. in thesec learly necessaryw ater bodies,b esides
Contraryt o the experienceo fBelkin (1968),b ut diminishingt he chanceso f successfuel stablish-
in agreementw ith that of Pillai (1979'), most ment by invadinge xotics.
(620,67Vo)o f the present survey's9 31 collec- The best consequenceso f such predation,
tions of larval Cr. peruigilans were from Cate- however, would be offset by the prevalence of
gory t habitats. The comparable figure for Ae. discardedt ires (from which notonectids, dytis-
notoscriptusw as9 5%. cids and corixidsw eren everc ollected)n ear air-
Of 37 different types of Category t habitats port and seaport likely reception areas and
dominated by these 2 species,d iscardedt ires throughout the urban and rural north. Until
(613)a nd stock drinking troughs (210)w ere by now, NZ's greatest threat from a Category 9
far the most numerousa nd widespread.B oth utilizer has beena ssumedt o be the cosmotrop-
abound throughout rural areas;t he former were ical or tropicopolitan (seeL ee et aL, lg87a\ Ae.
Iarva-positive at airports and seaports, and a aegypti.T his speciesw as establishedi n eastern
number of the latter yielded Cx. peruigilnns ad.- Australia (Skuse 1889)b y December1 882 ac-
jacentt o the perimeterso f both AucklandI nter- cordingt o Lee et al. (1987a)B. y the early 1900s
nationalA irport, Mangere,a nd Royal New Zea- (and possiblyl ong before)i t was in Fiji (Theo-
land Air Force Base,A uckland, at Whenuapai. bald 1903)a nd Samoa( Grunberg1 913).P erhaps
Both are clearly dangerousa s potential ovipo- Ae. aegypti is just a Iittle too tropical for NZ?
sition sites for newly imported Culicidae, and After all, Cx. quinquefasciatush as achieved a
neither proved anything like fully utilized. For greater latitudinal dispersion;y et it seemsf rom
190( 31%)o f the tires and 119( 57%)o f the stock data herein to be only just sufficiently tolerant
drinking troughs altogether lacked Culicidae, a of NZ's temperate conditions to have main-
fact that when addedt o the multiple-occupancy tained itself (with a high summer population
data presented earlier points to a prevailing peak) at and around the original ports of entry
availability of oviposition sites awaiting Cate- in the warmer northern districts. Yet, Ae. ae-
gory 9 larval habitat utilizers that might in gypti is still on the move, having only extended
future be accidentally imported into NZ. its ranget o NZ's tropical neighborso f Tokelau
Whether or not suche xotics haved irect sunlight and Niue as recently as the late 1960s,a ppar-
tolerance is a factor here, for most water held ently in consequenceo f importations during
by tires is shadedb y the rims (Fig. 8), while hurricane-reliefo perations( Piltai and Ramal-
most gravity-filleds tockt roughs( Fig. 10) are in ingam 1984,D ale and Maddison 1984).
open fields and unshaded.N ow the tire/trough Latterly, though, the prime threat has
occupancy rates exhibited by Cr. peruigilans, switchedt o the Asian tiger mosquito,a Stego-
"wide
with its exceptionally toleranceo f envi- myio second only to Ae. aegypti as a dengue
ronmental conditions" (Belkin 1968),w ere 40 hemorrhagicf ever virus vector and also able to
and,34%r, espectivelyw, hile thoseo f Ae. notos- transmit Ross River virus. For although of SE
criptus,w hich is as intolerant of direct sunlight Asian origin and until recent years regardeda s
in NZ (Graham 1929)a s in all possibles ource a purely tropical speciest,h is insect, following
countries (Lee et al. 1982),w ere 41 and 47o, its 1985a ppearancein the United Statesv ia the
respectively. usedt ire trade, has dispersedt o far from tropical
Another factor to be considered on the regionso f that country (Hawley 1988,A nony-
chanceso f successo f future mosquitoi nvasions mous 1989).T his suggeststh at Ae. albopictus
of NZ is predation. In that connection,f ield data (Skuse)m ight indeedb ecomee stablishedin the
sheetsf or 63 (53%) of the 119t roughsn egative warmer sector of NZ's North Island, once intro-
for Culicidae mentioned that predators were duced. Having done so, and differing from Ae.
common to abundant. Relevant samoleso cca- aegyptii n its well-known although not exclusive
sionally contained Corixidae,b ut thi dysticid (Laird and Mokry 1983)p redilection for peri-
beetle,R hantusp uluerosusw, as more common, domesticC ategory9 larval sites,i t wouldb e well
and the backswimmer,A nisopso ssimills,m ost placed for following such local paths as
common of all. The last-mentionedw ere fre- those already blazed by Ae. notoscriptusbackto
quently flightless morphs. Being unable to fly the diversity of Category 8 larval habitats that
from the habitat as winged notonectids can, it favors in nature in SE Asia (references in