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This study was undertaken as a Royal New Zealand Air Force research project, and is also distributed as RNZAF Entomological Bulletin No. 6. Authorized by Chief of Air Staff.
Entomologist, Medical Branch, Royal New Zealand Air Force.
The searching of 246 aircraft of seven military and civilian types on their arrival in New Zealand revealed that 88 (36 per cent.) had insect stowaways on board. A total of 548 insects collected included representatives of 56 Families and 10 of the 24 existing Orders, and nine spiders were also discovered. Houseflies comprised more than a third of the total catch, 190 of these being collected on 46 separate occasions. Other insects of health significance included 29 blowflies (in 19 aircraft), 28 mosquitoes (in 16 aircraft), 14 cockroaches (in 7 aircraft), and 2 fleas (in 1 aircraft). Actual or potential economic pests included numerous beetles, wasps, flies, and moths. Among these were species already established in, and native to, New Zealand, a fact underlining the danger that airborne insect introductions might be made from, as well as into, this country. Records are given of the carriage of insect eggs, larvae, and adults on the exterior of aircraft fuselages. Aircraft and airport insect control are discussed, with particular reference to measures enforced at Whenuapai Airport by the Medical Branch of the Royal New Zealand Air Force, on behalf of the New Zealand Health Department.
An extensive literature now exists with regard to the part played by aircraft in accidentally transporting insects from one airport to another, and so making possible the extension of the ranges of noxious species. In an earlier paper (Laird, Officers of the New Zealand Department of Agriculture will shortly be undertaking special insecticidal measures directed against agricultural pests on board aircraft arriving at Whenuapai and other New Zealand airports.
Whenuapai Airport, outside Auckland, is the chief New Zealand landing-ground for land-based aircraft arriving from abroad. Insects were collected from aircraft reaching this airport, also RNZAF Station, Ohakea, as time and opportunity afforded over the period
RNZAF orderlies search for insects on board aircraft which have arrived at Whenuapai from abroad, following the completion of insecticidal spraying (see page 26) and the subsequent disembarkation of the passengers and crew. The form filled out for each batch of material collected is illustrated below.
Insects Collected on Board Aircraft on Arrival at Whenuapai
IMPORTANT.—In cases where specimens are collected from two or more distinct stations on board the same aircraft, or where both living and dead material is obtained, make out a separate form for each batch of specimens. Use the same reference number for all material from the same aircraft, but differentiate the various batches by using a / sign, e.g., 207/1, 207/2, etc.
The use of the above form has proved most satisfactory in practice, and has allowed of the compilation of more precise data than would have been the case had simple aircraft/occurrence records alone been kept.
All of the twenty aircraft searched by the author in et al. (
Much of the material collected was of a fragmentary and dried-up nature, and had obviously been on board the aircraft concerned for considerable periods. Specific identifications were thus often precluded, although identification to the Family level was possible for all the specimens with the exception of some of the moths. The information derived from the sporadic
It will be seen from Table I that the total number of insects and spiders collected from only 8 multi-engined military aircraft (Lancastrian, Lincoln, Halifax, and York) was 69, equalling the total number found on board 119 multi-engined civilian machines (DC4 and DC6). Only 1 (12.5 per cent.) of the military aircraft was reported as insect-free, while 90 ( 75.6 per cent.) of the civilian aircraft were so reported. The overall average of specimens per aircraft for the 8 military machines was 8.6; and for the 119 civilian ones, 0.6. Sixty-seven (56.3 per cent.) of the 119 DC3 aircraft, all of which were military or ex-military transports, were listed as having no insects on board, while the remaining 52 (43.7 per cent.) contained 419 insects and spiders—75.2 per cent. of the total catch from aircraft of all types. The overall average of specimens per aircraft for DC3s was 3.5, while the average for the 52 DC3s from which insects were collected was 8.1.
The high average catch from the multi-engined military aircraft was largely due to the presence of accumulations of dead insects in the many extra harbouring places—gun turrets, for example—in these machines. The explanation of the marked difference between the figures for DC3s and those for DC4s and DC6s lies in the facts that the aircraft of the latter group, operated for the most part by Pan-American Airways and BOAC, have more smoothly finished interiors than the former military or ex-military transports and thus provide fewer sheltering places for insects; also that the large civilian machines are the more easily and thoroughly cleaned out between flights. At first sight the contrast between the high specimen/aircraft average for 43.7 per cent. of the DC3s and the complete absence of insects from 56.3 per cent. of these aircraft appears a most remarkable one. This is, however, due to the fact mentioned earlier that many aircraft were searched on several different occasions. In all cases the largest collections of insects were made from DC3s being searched for the first time, in consequence of accumulations of long-dead insects being found in the basal rims of astrodomes.
Taking the collections as a whole, the average number of insects for all 246 aircraft was 2.3, but from the above analysis it is evident that tittle significance attaches to this figure. Earlier investigators not having made a point of detailing the presence of accumulations of long-dead insects in their material (although frequent mention has been made of fragmentary specimens of specific interest), it is considered that little useful purpose is to be served by a detailed consideration of average numbers of insects collected during earlier projects in other parts of the world. That these averages differ widely is shown by the comparison of Whitfield's (
Table 2 shows that almost half (48.1 per cent.) of the specimens secured were collected from astrodomes, 40 (36.0 per cent.) of the total of 111 collections being from this station. During the daylight hours, the astrodome functions as a light-trap for positively phototropic insects. Gun turrets, also the windows of the main accommodation and pilot's compartments, function in a similar manner. Indeed, the bulk of the winged insects collected in these latter stations were found either on windows or on ledges and among the curtains of windows. The paucity of insects in toilet compartments is perhaps accounted for by the facts that the relative darkness of such windowless places in aircraft renders them unattractive to all but negatively phototropic insects and that frequently the only natural light penetrating here is that coining from ventilators opening to the exterior. Many winged insects, having entered toilet compartments, are doubtless attracted towards the light from the ventilators and so fly out of the aircraft.
No authority existed for the RNZAF orderlies to search privately owned luggage or cargo for insects. Judging by the discovery of 28 insects as a result of only four such collections made from easily accessible material, there is reason to believe that routine searches of luggage and cargo would reveal the presence of a considerable amount of entomological material. These 28 insects were found in crates of vegetables (ants and praying mantids) and flower leis brought by passengers from Honolulu (larvae of moths and flies). Travelling secreted within the plant material with which they came on board, they had escaped the effects of insecticidal spraying and thus would have had an excellent chance of becoming established here— particularly so as they would probably not have gained their freedom until they had been carried well beyond the reach of airport insect control. Baggage compartments opening to the exterior were found to contain a predominance of insects such as cockroaches and ants which had probably come on board with cargo, but also held actively flying insects such as midges and mosquitoes which doubtless flew up into them while they were open at overseas airports.
Of special interest was the discovery of moth-egg masses and emerging larvae on exterior surfaces of aircraft, a. note concerning which has already been published (Laird,
There has been some controversy as to whether adult insects are able to cling to the exteriors of aircraft fuselages during air journeys. Many insects are able to withstand very high wind velocities while clinging to plants in their natural habitats, and Davies (
It appears, therefore, that the danger of developmental and adult insects surviving air journeys on the exterior of aircraft fuselages is rather greater than had been realized.
Altogether, 548 insects belonging to 56 Families and nine spiders belonging to three Families were collected. These figures are not inclusive of the insect eggs and larvae discovered. Besides the pre-adult specimens already mentioned as being recovered from fuselage exteriors and passengers' effects, blowfly maggots were twice collected from kitchen garbage cans, and cockroach eggs were once found in a baggage compartment.
Reference to Table 3 indicates that houseflies and other muscid flies, numbering 190, comprised a little more than a third (34.7 per cent.) of the total number of insects collected. Earlier investigators agree with regard to the predominance of muscid flies in aircraft collections. Welch (Musca domestica and M. sorbens, comprised some 80 per cent. of his material from aircraft at Khartoum. Dethier (
Table 3 shows that five other Families were represented in 16 or more separate collections. These included mosquitoes and blowflies of medical and veterinary importance, also two Families of moths which number among their members many agricultural and domestic pests. Twenty-nine other Families were noted on from two to eight occasions, many of these thus being of quite frequent occurrence. Twenty-four others were recorded once only, and, judging by the diversity of material among these purely adventitious stowaways, also by the very large number of Families noted once only by earlier investigators, it is obvious that accidental stragglers from virtually any group might at some time or another enter or be carried into aircraft.
Only three of the 56 insect Families recorded above—the Chrysopidae, Sphecidae, and Chrysididae—have no indigenous or introduced New Zealand representatives, but, as will be shown later in the account, numerous species not found in this country were collected.
Up to the time of publication of Whitfield's ((Tetragnatha sp., Aranea spp., Lycosa spp., and Dolomedes sp.) are injurious to man, according to Mr. R. R. Forster, who kindly identified them for me. Six of them were orb-web spiders (Aranea spp.), and these had spun webs inside gun turrets and astrodomes. One of these webs, located in the rear gunner's turret of the RAF Lincoln Excalibur, which reached Ohakea from England on
As Table 4 indicates, first place in ordinal representation went to the Diptera, with 355 specimens (64.8 per cent. of the total insect catch). As already shown, this parallels the findings of previous investigators. The predominance of Diptera in aircraft collections is hardly surprising, for this Order is one of the largest in the Class Insecta and includes numerous abundant and often cosmopolitan species which are readily attracted to man and his habitations. Next came the moths— as in Whitfield's analysis of aircraft collection records up to
The first six insect Orders listed in Table 4—the Diptera, Lepidoptera, Hymenoptera, Coleoptera, Orthoptera, and Hemiptera—also occupy the leading six places (with differences in their relative order of abundance) in the lists published by Whitfield (
Specific identifications were made wherever the state of the material permitted and the necessary literature and check collections were available. Those species of known medical, veterinary, agricultural, or forestry significance (see Table 6) are considered separately in the four following sections of this account. The chief interest attaching to the species listed in Table 5 below lies in their present regional distribution. This table even includes some species regarded as beneficial in New Zealand and other lands. It is, however, open to question whether others of these insects would remain harmless if established in this country. As economic entomologists appreciate only too well, the most innocuous insect, once transported to a new locality and thus freed from the various physical and biological checks imposed upon it in its former habitat, is liable to multiply at a fantastic rate and become a redoubtable economic pest.
In order to allay any anxiety with regard to the number of insects in the following part of this account recorded as living, despite the fact that they were
Of the 22 species detailed in Table 5, 13 (59.1 per cent) do not occur in New Zealand. The chief air routes to this country pass through either Australia or the Hawaii-Canton Island-Fiji chain of airports, and the above table gives some idea of the variety of insects reaching New Zealand on board aircraft from these places. The record of a living example of Prohippelates pallidus (from the passenger compartment of a DC6 from North America,
The almost cosmopolitan domestic mosquito Aëdes aegypti, although widespread in Australia and throughout the larger islands of the Pacific, does not occur in New Zealand. This species is the classical vector of the causal organisms of yellow fever, which does not occur in the Pacific, also of those of dengue, which is rife in this area (again excepting New Zealand). A. aegypti was reported once only, a single living female being discovered in the passenger compartment of a DC3 which reached Whenuapai from Nausori, Fiji, on
Culex annulirostris, a most annoying evening-biting pest mosquito, is able to harbour the causal organisms of filariasis (Brug, C. annulirostris from this country is by Graham (C. annulirostris was recorded from aircraft at Whenuapai on five occasions, one live and five dead females and two dead males being collected. The living female was found in the forward luggage compartment of a DC4 which arrived from Sydney on
During Aëdes tongae were collected from the basal rim of the astrodome of a DC3 which had visited Tonga in the course of its previous flight. Farner and Bohart (Wuchereria bancrofti, the causal organism of filariasis in the South-west Pacific.
Culex fatigans, an important vector of W. bancrofti in many other parts of the world, is not considered so in the South Pacific and Indonesia. This species has long been established in New Zealand, and is particularly common in the vicinity of Auckland city and Whangarei, a fact supporting the hypothesis of ship-borne introductions having at one time been made (Graham, C. fatigans were recovered from the passenger compartments of two DC6 aircraft from Sydney (
There are several records of the human flea (Pulex irritans) from aircraft. Whitfield (P. irritans, and suggested that insecticidal sprays in aircraft do not normally reach these insects. Both the fleas found in the present instance were taken alive from a seat in the passenger compartment of a DC4 from North America during P. irritans is able to transmit the bacillus of bubonic plague under laboratory conditions, but most authorities agree that it is of little if any significance as a vector of this bacillus in nature.
Of the three vectors of human disease organisms recorded from aircraft at Whenuapai but not established in New Zealand, two would probably have but little difficulty in gaining a foothold here. Aëdes aegypti and Culex annulirostris are both widespread species able to adjust themselves to a considerable range of climatic conditions, and there is no reason to suppose that they Would not thrive in the more northerly parts of the North Island. However, there are grounds
Aëdes tongae to establish itself here, although field experiments would have to be conducted before this point could be finally settled.
Filariasis is a primarily tropical disease, and is endemic through the warmer and more humid regions of the world between the latitudes of 30° N. and 32° S. It is not considered that this disease could become established in New Zealand, and for that matter an efficient vector of the causal agent in its periodic form (Culex fatigans) already occurs here. Dengue, though, has a wider distribution. occurring from 36° N to 35° S. latitude in the Americas, and to a trifle north of 35° S. in Australia (Lumley and Taylor, Aëdes aegypti from the southerly parts of New South Wales, at a latitude equivalent to that of the most northerly parts of North Auckland. There is thus reason to believe that both dengue and the classical vector of its causal virus might be able to become established in at least this portion of New Zealand. Of course, the introduction of A. aegypti already infective for dengue is much more unlikely than that of uninfected mosquitoes. Following its establishment here the species might thus perhaps have only pest significance, until such time as infective mosquitoes, or dengue sufferers in the infective stage, slipped past the quarantine net.
By far the greatest danger to the health of man arising out of the development of air transportation in the South-west Pacific is that of the introduction of anopheline vectors of the plasmodia of human malaria into malaria-free lands. Anopheles is absent from New Zealand, Norfolk Island, New Caledonia, and the Pacific Islands east of 170° E. longitude, although both this genus and malaria are endemic in parts of Australia, in the New Hebrides and Solomon Islands, and throughout the Indo- Malayan region. The reasons for the absence of anopheline mosquitoes from such a broad area of the Pacific are incompletely understood. They may possibly lie in simple geographical isolation, or they may be bound up with physiological and/or ecological barriers which operate naturally to keep Anopheles outside this area. Until more is understood regarding this most important and fundamental problem, we must act as if geographical isolation is the only factor involved, and assume that species of this genus, once introduced into the malaria-free area, are capable of establishing themselves within it. Some support is undoubtedly lent this hypothesis by Lambert's (Anopheles and malaria, once introduced into isolated Rennell Island (south of the Solomons) in the late
Judging from chemical and climatic factors and macroscopic ecological features, there arc no apparent differences between ground pools in the New Hebrides and Solomon Islands utilized by Anopheles farauti Lav., a most efficient vector of the malarial organisms, and pools of similar type in such malaria-free localities as Fiji.
Culex annulirostris, for example, often shares larval habitats with A. farauti in the malarious Pacific Islands, and the former mosquito occurs abundantly in Fiji in ground pools which, superficially at least, appear suited to the requirements of this anopheline. Similarly, mosquito larval habitats in the northern parts of New Zealand, although possibly not suited to the tropical A farauti, outwardly appear suited to the requirements of more temperate anophelines, the Australian A. annulipes Walk., for example. The last-named species ranges through the whole of both coastal and inland Australia, according to Lee and Woodhill (A. annulipes does not normally transmit the malarial organisms in Australia, Roberts (A. farauti. Primary cases of malaria in Australia presumably transmitted by A. annulipes, have been reported from as far south as 37° S. latitude (Tebbutt. Anopheles capable of transmitting malarial parasites but not normally doing so in one area may be an important vector in another. Thus Chandler (Anopheles pseudopunctipennis Theo. is an apparently harmless mosquito, although this same species (possibly a different race) is the chief vector of malarial parasites in mountainous regions from Mexico to Argentina.
One thing is certain: if species of Anopheles capable of transmitting malarial parasites under the conditions prevailing in New Zealand and other parts of the malaria-free area of the Pacific ever become established here, a reservoir of infection will await them in the form of ex-servicemen and others who have contracted malaria abroad and still carry gametocytes in their blood. In Fiji in particular, where there is a large non-indigenous Indian population (many of whom are gametocyte carriers) as well as large numbers of Fijians who contracted malaria while serving in the Solomons during World War II, it is to be expected that the establishment of anophelines would be very quickly followed by primary malaria epidemics. There is an excellent historical precedent for such an eventuality. Hoops (Anopheles and malaria into the malaria-free areas of the Pacific, particularly into the less developed islands, would still be nothing short of a medical and economic disaster.
Although no anophelines have yet been collected from aircraft arriving in New Zealand from abroad, abundant instances of the carriage of these mosquitoes by aircraft are on record from other parts of the world. Galvāo (Anopheles gambiae Giles, one of the most deadly of the anophelines, has been shown by Sicé et al. (et al. (A. gambiae eradication campaign in Brazil—Soper and Wilson,
Five important mechanical carriers of organisms causing disease in man are listed in Table 6. Two of these are cockroaches, the cosmopolitan German Cockroach (Blattella germanica), which is already an abundant pest in New Zealand, and the American Cockroach (Periplaneta americana). The latter insect, although very common throughout most of the Pacific and sometimes found in New Zealand wharf sheds, does not seem to have gained a firm foothold in this country. Nine examples of the former species, two living and seven dead, were collected from the baggage compartments and kitchens of five aircraft from Australia, Norfolk Island, and Fiji, while five examples of P. americana, all living, were found in the baggage compartment of two DC4s from Fiji, where this insect is abundant. The medical significance of cockroaches is primarily concerned with food contamination.
It has been claimed that the causal organisms of tuberculosis, leprosy, amoebic and bacillary dysentery, and cholera may pass unharmed through the digestive tracts of cockroaches, while these insects may also act as the intermediate hosts of certain parasitic worms.
Stomoxys calcitrans, the Stable Fly, which now has an almost world-wide distribution and is common in New Zealand and other parts of the Pacific, can mechanically transmit the causal organisms of anthrax by its bite. The larvae of this species may also cause accidental myiasis in man (Smart, S. calcitrans was taken from the cockpit of a DC4 from Sydney on
The cosmopolitan housefly, Musca domestica, is abundant throughout New Zealand. Living and dead specimens definitely referable to this species were collected on 32 occasions in aircraft from Australia, Norfolk Island, Samoa, and Fiji. The number of individuals totalled 134, and no doubt many of the fragmentary muscid flies collected also belonged to this species. M. domestica and some of its close relatives are among the most important of all food contaminators. Among the pathogenic organisms causing disease in man which they have been shown to be able to carry on their mouthparts, their body hairs, and the pads of their feet, are those of typhoid fever, cholera, bacillary and amoebic dysentery, tuberculosis, yaws, conjunctivitis, trachoma, and septicaemia. These flies may also carry the eggs of such parasitic worms as whipworm and hookworm. Chandler (Fannia canicularis (dead examples of which were three times collected on board aircraft from Australia), is that larvae of this species have from time to time been reported from cases of intestinal and urino-genital myiasis in man (Smart, M. domestica has also been named in this connection.
A blowfly, Lucilia sericata, which is discussed in more detail in the following section of this account, has been shown by Chang (L. sericata has the habit of defecating while feeding. The cosmopolitan European Bluebottle, Calliphora crythrocephala, which some authorities consider to be at least of contributory importance as a food contaminator, was once collected alive from the astrodome of a DC4 from North America.
At first sight, fresh importations of the cosmopolitan species referred to above would seem to be without much significance. When, however, it is considered
Species of mosquitoes and wasps not found in New Zealand, and of potential pest significance, were collected during this project. A living female of Mansonia crassipes, a swamp-breeding mosquito common in parts of Fiji, was found in the astrodome of a DC6 from Nandi on Aëdes albolineatus, a jungle-breeding species occurring in the Indo-Malayan region and several of the Pacific islands, was collected from under a seat in the passenger compartment of a DC3 from Singapore; and a dead female of Culex sitiens, a widely distributed mosquito which breeds in brackish water, was taken from the astrodome of a DC3 on its arrival from Fiji and Norfolk Island on Aëdes albolineatus could find breeding places suited to its requirements in this country, but brackish swamps outwardly suitable as larval habitats for C. sitiens, a vicious biter known to have a long flight range in Fiji (Amos, M. crassipes, are adjacent to Whenuapai Airport, within easy reach of this species (which Amos states to have a flight range of at least one mile) from the tarmac.
Polistes olivaceus, a wasp common in Fiji (Williams, P. macaensis was collected (dead) in the passenger compartment of a DC4 from North America. Bonnet (P. macaensis among the medically important insects of Hawaii. A third vespid wasp, Ropalidia socialistica, was recorded (two dead specimens) from the astrodome of a DC3 from Malaya, via Brisbane. This species is stated by Tillyard (Salius bicolor is an Australian spider-hunting wasp, a single dead example of which was also found in the astrodome of a DC3 from Brisbane. The vespid records are of more than ordinary interest in view of the recent establishment of the German Wasp, Vespa germanica L., in the North Island of New Zealand. First reported from the Waikato district in V. germanica has become relatively more troublesome here than it is in its European home. Despite recent reports that this wasp is showing some beneficial qualities in that it has been seen destroying flies and moths, its fondness for sweetstuffs has made daytime jam-making rather a hazardous business for housewives living in the invaded districts, and it has now taken to robbing beehives and destroying hive nuclei in the autumn (Paterson, V. germanica has spread to Whenuapai, where its nests are continually being located and destroyed within airport bounds by the RNZAF insect-control unit, and it has recently been reported as entering aircraft there. This introduces the danger that, unless constant vigilance is exercised, V. germanica may be transported by means of aircraft both to the South Island of New Zealand and to other parts of the Pacific area. The natural preoccupation with the risks of insect introductions attendant upon international air transportation has tended to overshadow the parallel risks from internal air transportation. Although the latter risks may all too easily be regarded merely as an acceleration of the inevitable, due regard should nevertheless be paid to them.
The wasting disease of dogs known as heartworm or canine filariasis, caused by the nematode Dirofilaria immitis, is absent from New Zealand. In order to guard against its importation, together with that of other causal organisms of canine diseases, dogs may only be brought into this country under rigid quarantine regulations. Among the vectors of D. immitis are Aëdes aegypti and Culex fatigans (Del Rosario, Pulex irritans (Summers, D. immitis. Heartworm thrives in both warm and temperate climates, and there is a decided possibility that it could become endemic at least in the northern parts of the North Island, locally bred C. fatigans and P. irritans serving to spread the disease.
Aëdes aegypti, Culex fatigans, and Stomoxys calcitrans are all known vectors of the virus which causes fowl-pox, and the first-named species may also transmit equine encephalomyelitis. Here again, there is a possibility that epidemics of these diseases might be originated in the farmlands adjacent to New Zealand airports, following the introduction of infective insects.
The species of the Family Calliphoridae listed in Table 6 are all known sheep maggot flies. Calliphora laemica and Lucilia sericata are the primary sheep maggot flies in New Zealand (Miller, Lucilia cuprina is the most important primary species in Australia (Mackerras, C. laemica, a species native to New Zealand but not found in Australia, entered a DC4 following its arrival from the latter country in L. sericata were collected from a garbage can in the kitchen of a DC6 which arrived at Whenuapai from North America on L. cuprina, an almost cosmopolitan species which has been introduced into that country (Bezzi, Calliphora erythrocephala and C. rufipes were taken alive in the astrodome and passenger compartment of a DC4 from North America, although there is a possibility that these may have flown on board following the completion of insecticidal spraying at Whenuapai. A single dead example of Chrysomyia rufifacies found in the passenger compartment of a DC6 from North America might have come on board at the airport in either Hawaii (Bryan,
The sheep maggot fly problem is of great importance to both Australia and New Zealand, the prosperity of which is so closely bound up with sheep-raising. The possible interchange between the Pacific islands and these countries of not only new species of sheep maggot flies but also dangerous strains of species already represented by harmless strains is obviously rendered possible by air transportation.
Two agricultural pests found in New Zealand, one native to this country and one cosmopolitan, figured among the collections made from aircraft at Whenuapai. Eucolaspis brunnea, the indigenous Bronze Beetle, which formerly fed on foliage of various native plants, now does considerable damage to crops of apple, pear, and smaller fruits in this country, serious infestations resulting in the loss of more than 40 per cent. of the annual crop (Lysaght, E. brunnea) of a species which causes serious damage to beans, on board aircraft following their arrival in Texas from Mexico. Again, Bruchus rufimanus, the widespread Broad Bean Weevil which is an introduced pest in both Australia and New Zealand (Tillyard,
Prodenia litura is a widely distributed noctuid moth found in Australia and several islands of the Pacific, but not in New Zealand. The larvae of this species cause havoc among vegetable and other crops in various parts of the world. Among the more temperate of their food plants in Fiji are egg-plant, Acacia flowers (Veitch. P. litura is absent from Hawaii, reported that moths of this species sometimes fly into aircraft at night on Canton and Midway Islands. The same author (P. litura on board aircraft reaching Honolulu from these island bases. During P. litura would not become a major economic pest if once it became established in New Zealand.
Recent examples of the introduction of plant pests into new habitats, presumably by means of aircraft, concern Hawaii and Africa. Kevan (Gonipterus scutellatus Gylh., among eucalypts in Kenya and Eastern Uganda, and considered that an introduction by air from South Africa had taken place at Kisimu Airfield. The second instance, of considerable significance from the New Zealand point of view, is that of the recent establishment of the Oriental Fruit Fly (Dacus ferrugineus var. dorsalis Hend.) in Hawaii. Pemberton (
The only insect of definite forestry significance found in aircraft at Whenuapai during the period under review was the European Wood Wasp, Sirex noctilio, a serious pest in exotic pine forests in New Zealand. Rawlings (S. noctilio probably became established in this country prior to 190, having been imported with timber from Europe, and thought it likely that later introductions probably followed the initial one. During S. noctilio was found on the floor of the passenger compartment of a DC3 engaged on the Norfolk Island run. This occurrence raises the possibility that wood wasps entering aircraft at Whenuapai—having originated in the exotic pine shelter-belts on farmlands bordering the airport—might be transported to adjacent countries at present free from this important species. In Australia in particular, careful precautions are being taken in an endeavour to prevent the introduction of Sirex, and a recent newspaper report detailed costly fumigation and heat treatment ordered by the Commonwealth authorities for cargoes of Sirex-infested timber which had arrived by sea from Europe.
Duguet (
Insects in aircraft may be controlled by means of fumigation, aerosol mists, and residual insecticides. Duguet (
The insecticidal efficiency of chemical sprays is intimately bound up with droplet size and diffusibility, and the relatively large liquid droplets dispersed in the form of a limited cloud by outmoded pump-type spray guns render the latter of very little value for use in aircraft. The only sprays which can be considered of sufficiently high insecticidal value for use in aircraft are those dispersed in aerosol form—David and Tew (
Aerosol dispensers may be portable and manually operated or built in and either manually or automatically controlled. While built-in spraying systems (see Duguet, 2-propelled refillable aerosol dispenser. While it was found that this apparatus is of very uniform performance and permits the projection of an accurately measured dose, it proved that the insecticide involved had the grave disadvantage of containing an important crazing agent, methylene chloride.
Tew et al. (
All aircraft arriving at Whenuapai Airport from overseas are boarded by an RNZAF orderly, who proceeds to spray them throughout by means of an aerosol "bomb." Following the completion of spraying, the doors and windows of the aircraft must remain closed for a period of five minutes, to ensure that the aerosol mist is not dispersed prematurely, before disembarkation and unloading take place. Before boarding the aircraft, the orderly directs spray into the wheel cavities, and following disembarkation he also sprays any external baggage compartments and makes a visual inspection of the exterior of the fuselage with the object of locating any insect nests or egg masses which may be present. In addition, he thoroughly searches the aircraft for insect remains, which are forwarded to Air Department for entomological examination (see page 3).
The above measures afford a high degree of protection against accidental introductions of insects being made by means of aircraft. As long as spraying on arrival continues to be our chief means of protection against airborne introductions of insects, however, the chance remains that insects carried on the outside surfaces and in wheel cavities of aircraft might escape during, or immediately following, landing. Furthermore, there is a danger that winged insects travelling within the aircraft might escape through the door as it is opened to admit the spraying orderly. That these risks are of significance is shown by the fact that flight experiments carried out with Aëdes notoscriptus proved that this mosquito is active in the period during and immediately following landing in response to the stimuli of a sudden increase in air temperature and air pressure followed by a cessation of vibration as the motors are stopped (Laird,
In order to provide a further measure of protection by ensuring that any mosquitoes which might thus escape from arriving aircraft are denied nearby larval habitats, all actual and potential mosquito-breeding places within the bounds of RNZAF Station, Whenuapai, are regularly treated with DDT-base larvicides. A monthly mosquito-control report is forwarded to Air Department, together with specimens of any batches of mosquito larvae located. To date, the only larvae resulting from these collections have been those of the common local mosquitoes, Aëdes notoscriptus, Culex fatigans. and C. pervigilans Berg. An additional measure which might lead to the discovery of an insect introduction at an early enough stage for effective remedial action to be taken is that RNZAF personnel at this airport are encouraged to send forward specimens of any unusual insects which they see at Whenuapai so that these can be identified. Once again, all such insects so far identified have proved to be local species.
The control of insects at international airports is usually confined to mosquitoes, and quite frequently to one particular species of mosquito known to be dangerous locally. Thus, at Nandi, Fiji's international airport, particular attention is paid to the control of Aëdes aegypti, a species which the author failed to discover there during a visit in Culex annulirostris and C. fatigans were found to be very abundant in ponded drainage ditches near the airstrips at Nandi; and during the evenings adults of both these species, also of Mansonia crassipes which breed in the extensive swamps on the Nandi Plains, were collected in the airport sleeping quarters. C. annulirostris, C. fatigans, and A. aegypti were all found to be breeding at Nausori Airfield, which is used as a landing field for RNZAF aircraft. The collection of examples of all four of the species named above from aircraft which reached Whenuapai from Fiji in