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Insects Collected from Aircraft Arriving in New Zealand from Abroad

General Account of the Material Collected

General Account of the Material Collected

Table 1
Collecting Records By Type of Aircraft
Type of aircraft Category* Total Number searched Number containing insects and spiders Number of insects and spiders
DC3 (C47, Dakota) M & C 119 52 419
DG4 (C54, Skymaster) C 72 13 36
DC6 C 47 16 33
Lancastrian M 3 2 11
Lincoln M 2 2 29
Halifax M 2 2 26
York M 1 1 3
Totals 246 88 557

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.

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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 (1939) figure of 1.5 (from the examination of 2,000 aircraft in Africa over a three-year period) with that of 33.5 from Pemberton's (1944) analysis of the collections from 321 aircraft returning through Honolulu from the South Pacific and the Orient during a period of similar length.

Table 2
Number of Collections Made from Each Principal Station Investigated, and Number of Specimens Found in Each Station
Station Number of collections Number of specimens
Astrodome 40 268
Main accommodation compartment 32 145
Gun turrets 7 50
Baggage compartments 14 38
Luggage and cargo 4 28
Pilot's compartment 8 23
Toilet compartment 4 5
Exterior of fuselage 2 many eggs and larvae
Totals 111 557

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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, 1950). Such egg masses were found on two occasions during 1950, once on the aerial on the underside of the nose of a DC3 from Nausori, Fiji, and once beneath the wings of another DC3 from Nandi, Fiji. Similar occurrences had previously been noted in Trinidad, British West Indies (Senior White and Kirkpatrick, 1949) and in Aitutaki and Western Samoa (Dumbleton, 1950), the first-named authors drawing attention to the danger that larvae emerging from such egg masses could easily be swept away during flight and so be deposited over large tracts of countryside. In the cases noted by Senior White and Kirkpatrick and by the author, the larvae concerned were identified as belonging to the Family Noctuidae, many members of which are serious pests of agricultural crops.

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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 (1936) demonstrated that aphides are able to cling to the glass lining of an experimental wind tunnel while withstanding a wind velocity of 70 m.p.h. While admitting that older types of airliners provided possible external resting-places for insects (projections such as fixed undercarriages, for example, behind which pockets of relatively calm air might exist during flight), Whitfield (1939) considered that modern streamlining renders the carriage of insects on fuselage exteriors impossible. However, such carriage of adult insects has been observed in the South Pacific. Thus, a passenger on board an RNZAF DC3 travelling from Fiji to Aitutaki shortly after the end of World War II saw an insect which he thought to be a beetle alight on the outside of the fuselage near his window at take-off and remain there throughout the flight. Following the landing at Aitutaki, he collected the insect, which was still alive. Unfortunately, this specimen was subsequently mislaid. A most interesting observation of another such occurrence was made by the New Zealand Director of Civil Aviation, Mr. E. A. Gibson. In March, 1946, Mr. Gibson piloted a DC3 from Faleula, Western Samoa, to Nausori, Fiji. During take-off, an insect about three-quarters of an inch in length, and which from his description was almost certainly a beetle, struck the windshield in front of him and clung to the perspex. Mr. Gibson attempted to dislodge it by means of the windscreen-wiper, but it merely crept to the bottom of the windscreen and remained there, appearing as if dead, throughout the 710-mile flight, during which an altitude of 9,000 ft. was maintained. After the landing at Nausori, and while the aircraft was still taxi-ing, the insect suddenly spread its wings and flew away.

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.

Table 3
Families of Insects and Spiders Collected

(in order of family incidence)
Family Number of occasions on which collected Number of individuals
Muscidae (houseflies) 46 190
Noctuidae (owlet moths) 24 36
Chironomidae (midges) 19 41
Calliphoridae (blowflies) 19 29
Culicidae (mosquitoes) 16 28
Tineidae (leaf-miners, clothes moths, etc.) 16 22
Tachinidae (scavenger flies) 8 12
Anthomyiidae (lesser houseflies, etc.) 8 11page 8
Vespidae (social wasps) 8 11
Mycetophilidae (fungus gnats) 8 10
Ichneumonidae (ichneumon flies) 8 8
Blattidae (cockroaches) 7 14
Unidentifiable moths 7 12
Tipulidae (crane flies) 7 8
Argiopidae (orb-web spiders) 6 6
Tortricidae (bell moths) 4 4
Formicidae (ants) 3 14
Mantidae (praying mantids) 3 13
Braconidae (supplementary ichneumon flies) 3 5
Scarabaeidae (chafer beetles) 3 4
Chrysomelidae (leaf beetles) 3 4
Syrphidae (hover flies) 3 4
Stratiomyiidae (soldier flies) 3 3
Cerambycidae (longicorn beetles) 3 3
Bruchidae (pea and bean weevils) 2 8
Chrysididae (ruby wasps) 2 3
Crambidae (grass moths, etc.) 2 3
Drosophilidae (fruit flies, etc.) 2 3
Micropterygidae (primitive moths) 2 2
Pentatomidae (shield bugs) 2 2
Coccinellidae (ladybird beetles) 2 2
Curculionidae (weevils) 2 2
Trypoxylidae (house wasps, etc.) 2 2
Apidae (bees) 2 2
Rhyphidae (false crane flies) 2 2
Lycosidae (wolf spiders) 2 2
Ortalidae (mottled-wing flies) 1 5
Thripidae (thrips) 1 2
Sciomyzidae (sciomyzid flies) 1 2
Oscinidae (eye flies, etc.) 1 2
Pulicidae (fleas) 1 2
Forficulidae (earwigs) 1 1
Membracidae (tree hoppers) 1 1
Aleurodidae (white flies) 1 1
Hydrophilidae (water beetles) 1 1
Staphylinidae (rove beetles) 1 1
Siricidae (wood wasps) 1 1
Sphecidae (thread-waisted wasps) 1 1
Trichopterygidae (feather-wing beetles) 1 1
Anthribidae (broad-snouted weevils) 1 1
Psammocharidae (spider-hunting wasps) 1 1
Chrysopidae (green lacewings) 1 1
Coniopterygidae (small lacewings) 1 1
Psychodidae (moth midges) 1 1
Bibionidae (March flies) 1 1page 9
Cecidomyiidae (gall gnats) 1 1
Bombyliidae (bee flies) 1 1
Dolichopodidae (long-legged flies) 1 1
Phoridae (hump-backed flies) 1 1
Pisauridae (nursery-web spiders) 1 1

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 (1939) found the housefly to be the most prevalent insect on board aircraft arriving at Miami, Florida, while Whitfield (1939) indicated that muscid flies, chiefly Musca domestica and M. sorbens, comprised some 80 per cent. of his material from aircraft at Khartoum. Dethier (1945) stated that of more than 2,000 insects which he recorded from aircraft in Central Africa during 1943–45, 88.5 per cent. were Diptera (mostly Muscidae), and Mendonça and Cerqueira (1947), who dealt with a total of 40,168 insects collected from aircraft which arrived in Brazil during 1941–45, listed 37,428 (93.2 per cent.) of these as Muscidae. This Family also led easily as regards the total number of occasions on which its members were found, in the present project as well as in the earlier ones just mentioned.

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.

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Up to the time of publication of Whitfield's (1939) review, only two spiders had been recorded from aircraft (by Welch, 1939). Subsequent investigations have revealed that these animals are more commonly carried by aircraft than was previously realized. Thus Mendonça and Cerqueira (1947) found 153 spiders amongst the material which they studied in Brazil. None of the nine spiders collected during the present project (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 23rd September, 1946, proved an unexpected supplement to insect control, for it contained the remains of some Diptera, including a still-struggling ceratopogonid midge.

Table 4
Orders of Insects and Spiders Collected
Order Number of Families Number of individuals
Diptera (two-winged flies) 20 355
Lepidoptera/Heteroneura (moths) 5 79
Hymenoptera (ants, wasps, bees, etc.) 11 49
Coleoptera (beetles) 10 27
Orthoptera (cockroaches, mantids, etc.) 2 27
Araneida (spiders) 3 9
Hemiptera (true bugs) 3 4
Neuroptera (lacewings, etc.) 2 2
Aphaniptera (fleas) 1 2
Thysanoptera (thrips) 1 2
Dermaptera (earwigs) 1 1
Totals 59 557

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 1939—with 79 individuals (14.4 per cent. of the total insect catch). The majority of this group belonged to the two dominant Families of the Lepidoptera/Heteroneura, the Noctuidae and Tineidae. The former Family is for the most part made up of night-flying species, and its representatives were probably attracted to the aircraft page 11 concerned while lights were on during night stops or night servicing. The majority of the Tineidae are active during the daytime, when moths of this Family often fly into aircraft from nearby vegetation. Third and fourth places in the list are held by the Hymenoptera and Coleoptera, which exhibited a more diverse Family representation than did the Lepidoptera. Although as many individual orthopterans as coleopterans were collected, these belonged to but two Families and mostly came on board with cargo, in contradistinction to the great majority of the four Orders already mentioned, which had obviously flown on board under their own power.

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 (1939) and Dethier (1945). Taken collectively, they account for 98.7 per cent. of the present insect collections, for 99.7 per cent. of the material analyzed by Whitfield, and for 99.45 per cent. of Dethier's material. The predominance of these six Orders in aircraft collections is merely a reflection of their incidence in nature, for they occupy the commanding positions among the 24 existing insect Orders. It is obvious that the relative representation of the six leading Orders may vary with locality and with the relative proportions of day and night activity along air routes; night-time activity on board grounded aircraft favouring the entry of nocturnal species of the Diptera, Lepidoptera, and Coleoptera in particular, day-time activity favouring that of diurnal representatives of these same Orders and also that of members of such largely diurnal Orders as the Hymenoptera and Hemiptera. Finally, it is only to be expected that members of the less numerically abundant Orders and of species (other than predominantly domestic ones) distinguished by markedly cryptic habits comparatively seldom have the opportunity of entering aircraft.

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 page 12 collected following insecticidal spraying, it is as well to state here that the majority of such specimens were incapacitated from the effects of the spray when discovered. Even if they were exhibiting only the slightest movement they were recorded as living, in order that they could be accurately differentiated from insects which had been killed by earlier sprayings but had been overlooked by the cleaners.

Table 5
Insect Species of Non-Economic Significance Collected

(Those marked with an asterisk were alive when found.)
Species and systematic position Number found Number of times found Pacific and Australasian distribution (as affecting N.Z. air routes only)
DERMAPTERA
Forficulidae
Forficula auricularia L. 1 1 Cosmopolitan
HEMIPTERA
Pentatomidae
Cermatulus nasalis Wwd. 1 1 N.Z., Australia
COLEOPTERA
Coccinellidae
Cryptolaemus montrouzieri Muls. 1 1 Australia, Fiji, Hawaii
Trichopterygidae
Ptenidium lawsoni Matt. 1 1 N.Z.
HYMENOPTERA
Ichneumonidae
Lissopimpla semipunctata Kby. 4 4 N.Z., Australia, Fiji
Echthromorpha intricatoria Fabr. 1 1 N.Z., Australia
Paniscus productus Brul. 1 1 Australia
Chrysididae
Pentachrysis imperiosa Sm. 3 2 Australia
Stilbum splendidum Fabr. 1 1 Australia
Formicidae
*Pheidole megacephala (Fabr.) 2 1 Fiji, Samoa, Hawaii
Trypoxylidae
Pison spinolae Shuck. 1 1 N.Z., Norfolk Id. Aus.
Pison ignavum Turn. 1 1 Australia, Fiji, Samoa
DIPTERA
Rhyphidae
Rhyphus neozelandicus Sch. 2 2 N..Z, Australia
Bibionidae
Dilophus nigrostigma Walk. 1 1 N.Z.
Stratiomyiidae
*Neoexaireta spinigera Wied. 1 1 N.Z., Australia
Syrphidae
*Xanthogramma javanum var, distinctum Kert. 1 1 Australia, Fijipage 13
Chloropidae
*Prohippelates pallidus (Loew) 1 1 Fiji, Cant. Id., Hawaii
Tachinidae
*Sarcophaga dux Thom. 3 2 Fiji, Cant. Id., Hawaii
Sarcophaga tryoni J. & T. 1 1 Australia
LEPIDOPTERA
Tineidae
*Petrochroa dimorpha Busck. 2 1 Canton Id., Hawaii
Nemotois sparsella Walk. 1 1 Australia
Noctuidae
Earias smaragdina Butl. 1 1 Australia

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, 7th July, 1950) is of particular interest in that Van Zwaluwenburg (1943) noted that this fly was "sometimes very numerous aboard (sea)planes while moored at Canton during the day."

Table 6
Species of Medical or Economic Significance Collected

(Those marked with an asterisk are already established in New Zealand; M denotes medical, V veterinary, A agricultural, and F forestry significance.)
Species and systematic position Significance
ORTHOPTERA
Blattidae
Periplaneta americana L. M
*Blattella germanica L. M
COLEOPTERA
Chrysomelidae
*Eucolaspis brunnea Fabr. A
Bruchidae
*Bruchus rufimanus Bohem. A
HYMENOPTERA
Siricidae
*Sirex noctilio Fabr. F
Vespidae
Polistes olivaceus (De Geer) M
Polistes macaensis (Fabr.) M
Ropalidia socialistica Sauss. M
Psammocharidae
Salius bicolor Fabr. Mpage 14
DIPTERA
Culicidae
Mansonia crassipes van der Wulp M
Aëdes aegypti (L.) M, V
Aëdes albolineatus (Theo.) M
Aëdes tongae Edw. M
Culex annulirostris Sk. M.
*Culex fatigans Wied. M, V
Culex sitiens Wied. M
Anthomyiidae
*Fannia canicularis L. M
Muscidae
*Musca domestica L. M
*Stomoxys calcitrans L. M, V
Calliphoridae
*Calliphora erythrocephala (Meig.) M, V
*Calliphora laemica (White) V
*Calliphora rufipes (Macq.) V
*Lucilia sericata (Meig.) M, V
Lucilia cuprina Wied. V
*Chrysomyia rufifacies Macq. V
APHANIPTERA
Pulicidae
*Pulex irritans L. M, V
LEPIDOPTERA
Noctuidae
Prodenia litura Fabr. A

* M & C, military and civilian; C, civilian; M, military.