REPORT ON MOSQUITO INVESTIGATIONS.

Manawatu Herald, Volume XLI, Issue 1939, 13 February 1919, Page 4

REPORT ON MOSQUITO INVESTIGATIONS.

(By Mr. David Miller, Entomologist, in The Journal of Public Health.) The following is the report on the preliminary observations made in the Auckland District in connection with the mosquito Investigation commenced during the summer of 1016-1917'. .

Owing to the severity of the weather and floods during the greater part of my visit 1 was considerably handicapped in making detailed observations on the larval stages of the mosquitoes captured, confining myself mainly to the collecting of adults and the location ot their •breeding-grounds. At present it cannot be definitely stated that the yellow-fever mosquito (Stegomyia fasciata) or any of the malarial species (Anophelines) do or do not- exist in the Auckland district, although, as will lie seen below, there are indications in certain localities that Anophelines have become establishd. In any case, it has been found that the environiunt of the Auckland District is suitable for both S. fasciata and the Anopholines. The various places discussed will he mentioned in the order in which they were visited. In Auckland City mosquitoes abound in such large numbers as to be of great annoyance to the population. This abundance is, beyond doubt, due to the many collections of Avater available for breeding-, grounds which are to ho found throughout the city. Examples ul such are the catch-basins for .-iufaco water in the streets; largetanks above buildings for fire purposes 5 the brackish water, in main parts, which collects around the coast of the harbour; old tins, etc. As outstanding sources of infestation may be mentioned the sleep gully beneath the Grafton Bridge, where water and ooze accumulate, and in Avhieh the larvae are to he found in large numbers. Again, m Bcresford Street, Avhere the Auckland Gas Company’s gasometer stands, at the bottom of a deep depression, there is a large pool of stagnant water frequented by mosquitoes, This depression is surrounded by a well-populated area, and ou one side is partially lijle<? and used as a dump for rubbish, old tins, etc., the latter in particular being in evidence, and containing Avater in sufficient quantity for the purpose of the mosquito life. Also, this dump is infested Avilli rats, many being seen lying dead and breeding hosts of house-lly maggots. The ponds in the various parks are a source of mosquito infestation unless Avell stocked with small fish. The city may also he infested with mosquitoes earned by Avinds or Hying in from breeding-grounds in the surrounding country or suburbs. At St. John’s Lake, iu the suburb of Remuera, larvae abound, and the adults arc very severe in their attacks in this suburb. This lake, 1 believe, is being drained or partially drained: hut in order to completely eradicate the mosquitoes from this part the water should be altogether removed, or confined to such a small area as to render such a control method as oiling practicable. Around the margins of the lake, Avliere cattle or horses arc in the habit of drinking, the soft ground is coA'eml with the depressions caused by the hoot's of these animals; in such places the Avater has collected and mosquito larvae abound.

Devonport, Takapuua, etc., also suffer from the attacks of mosquitoes. lu one ease at Devonport enormous numbers of larvae were in an open surface drain where it entered the niud-flut left dry at loav tide. On the other hand, at Takapuna and those suburbs along the coast the attacks were due to a large extent to a unique form of mosquito, Avhieh will have to lie placed in a new genus, which breeds in the brackish pools along the coast above high-Avater mark. At (he lime of my visit 1 was unable to find any larvae in Taka puna Lake. As a typical example of breedingground mention may he made of the sAvampy tint in the A'ieinity of the Devonport racecourse. At the Bay of Islands the mosquitoes Avero in marked evidence. They Avere not only found breeding in tanks of drinking-Avator, old tins, etc., hut also extensively in the patches of swampy country in the vicinity and in the still pools of streams and roadside ditches. In one of the streams Avere found some larvae of the structure of Anopheles, but owing to the specimens being carried about from place to place they died before breeding out. The unique mosquito found along the coast-line at Takapuua, etc., aboumled here in large numbers in the pools amongst’the rocks. The area contained in the valley betAveen Opua and Hikurangi is one of the largest mosquito-breeding grounds visited. 'This locality is, on the whole, very wet, and in part covered by Avhite-pine forest. In the pools of the various streams feeding this valley, particularly those sheltered by forest or scrub, larvae abound in large numbers. The stream running through Opua is very sluggish, and Avhcn in Hood covers the surrounding loAv-lying count it.

At Whangarei the mosquitoes breed in the surrounding streams and in the usual collections of Avater to be found in the toAvn itself. The adults may also be carried from the outlying swamp areas. Whangaroa Avas not seriously affected by mosquitoes during my visit, although some Avere to bo found in the pools left by dried-up streams. The surrounding country is very steep, Avith large areas of

forest. At the head of the harbour and in several inlets are extensive mud-flats where there eolleets hrakish water, hut even in such places mosquito larvae and adults were neither absent or very scarce. At Kaitaia is an extensive whitepine swamp abounding in mosquitoes. Through this swamp runs a stream which gives rise to extensive floods. In the surrounding forest -covered hills mosquitoes arcvery common, particularly whore a stream runs into a swampy area. In such a sheltered place two mosquitoes were observed which strongly resembled the genus Anopheles, hut unfortunately 1 was unable to capture them. They were apparently uncommon, since, although considerable time was spent looking for specimens both during the day. and after they were not seen again. A considerable number of mosquitoes was collected, hut owing to the unsatisfactory state of the literature at hand dealing with the subject it would be advisable to delay their systematic descriptions until trustworthy works are available.