THE MOSQUITO

Dominion, Volume 12, Issue 79, 28 December 1918, Page 8

THE MOSQUITO

HIS HAUNTS AND HABITS PARTICULARLY OFFENSIVE IN AUCKLAND

In the current "Journal of Public Health," Mr. David Miller, entomologist, contributes the following report on lys mosquilu investigations in Nuw Zealand on buliiitt of tliii Uovurnmeiil:— Tho luljowing is the report on the preliminary observations n.ade in the Auckland district in connection with the mosquito investigation commenced during the summer ot IIH6-17. Owing to the severity of the weather and floods during the g>enter part of my visit, 1 was considerably handicapped in milking detuned observations on the larval stages of the mosquitoes captured, confining myself mainly to the collecting of adult; and the location of their breeding grounds. At present it cannot be definitely stated that the yellow-fever mosquito (Stegomyin fasciata) or r.ny of tho malarial species (Anophelines) do or do ncTt exist in the Auckland district, although, as will be seen below, there are indications in certain localities that Anophelines have become established. In any case it has been found that the environment of the Auckland district is suitable for both S. fnsciata and the Anophelines. The various places will be mentioned in the order in wFch 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 irater available for breeding grounds which are to be found throughout tho city. Examples of such are the catch-basins for surface water in the streets; large tanks above buildings for firo 'purposes; the brackish water, in many parts, which collects around the coast of the harbour; old tins, etc. As outstanding sources of infestation may bo mentioned the steep giillv beneath the Grafton Bridge, where water and ooze accumulate, and in which the larvae are to be found in lnrge numbers. Again, in Bcresford Street, where tho 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 on one side is partially filled and used as a dump for rubbish, old tins, etc., the latter in particular being jn evidence, and containing water in sufficient quantity for the purpose of the mosquito life. Also, this dump. is infested with rats, many beinj; seen and breeding hosts of house-fly maggots. The ponds in the various parks are a 6onrce of mosquito infestation unless well stocked with small fish.

The city inay also be infested with mosquitoes canned by winds or flying in from breeding grounds in the surrounding country or suburbs. At St. Jonn h 1.M1u , . in tiie suburb of Rcuiuern, larvae abound, and the ndult.i are very severe in their attacks in i.his suburb. This lake, I believe, is being draiued or partially drained( but in order to completely eradicate the mosquitoes from this part the water would have to be altogether ■removed, or confined to such, a small area as to render 6uch a control method as oiling ■ practicable. Around (lie margins of the 'alte, where cattle or ■horses are iu the habit of drinking, the soft ground is covered with the deprraeions caused by the Loofs of these animals; in such places the water has collected and mosquito larvae abound. Devonport, Takapuna, etc., "also suffer from the attacks of mosquitoes. In one case at Devonport enormous numbers of larvae were in an open surface drain where it entered the mud-flat left dry at low 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, winch will have to be placed in a new genus, which breeds in the brackish pools along the coast above high-water mark. At the time of my visit I was iiliable to find any larvae' in Takapuna Lake. As a typical example of breeding ground mention may be made of the swampy flat in tho vicinity of the Devonport racecourse

At Hio Bay of Tslnmlg the mosquitoes were in marked evidence. They were not only found breeding in tanks'of drinking wnter, old tins, etc., but also extensively in the patches' of swampy country in tho vicinity and in the still pools of streams and roadside ditches. In one of the streams were found some larvae of the structure of Anopheles, but owing to the specimens being carried about from place to place- they cied before breeding out. The unique mosquito found along the coast-lino at Taknpiinn, etc., abounded hfre in large numbers in the pools amongst the rocks.

The area contained' in the valley between Opua and Jlikurangi is one of the largest mosquito-breeding grounds visited. This locality is, on the whole, very wet, and in part covered by white 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 when in flood covers the surrounding low-lying country. At Whangaroi the mosquitoes breed in the surrounding streams and in the usual collections of water to be found in the town itself. Tho adults may also be carried from the outlying snviimp areas. Whangaroa was not seriously afferjj-d by mosquitoes during niy visit,' although some wore to be found in the pools left by dricd-iip streams. The surroundini; country is very steep, with liircre areas of forest. At tho head of the harbour and in several inlets arc extensive mud-flats where there collects brackish water, but even in such places mosquito larvae and adults were eithor absent or very scarce. At Kaitaia is an extensive white-pine swamp abounding in mosquitoes, Through this swamp runs a stream which gives rise'to extensive floods. In the surrounding forest-covered hills mosquitoes aro very common, patlicnlarly where a stream runs into a swampy area. In such a sheltered place two mosquitoes were observed which strongly resembled the genus Anopheles, but unfortunately I was unable to capture them. Thev were apparently uncommon, .since, although considerable time, was spent looking for specimens both during the day and after they wero lot seen again. A considerable number of mosquitoes was collected, hut owing to the unsatisfactory state of tho literature <it hand dealing with the subject it would be advisable to delay their systematic descriptions until trustworthy works are available.