THE MOSQUITO

Waikato Independent, Volume XXX, Issue 2304, 27 February 1930, Page 6

THE MOSQUITO

A POSSIBLE MENACE

NEED FOE PRECAUTIONS

In view of the prevalence of mosquitoes in the Cambridge district of late years, and especially during- dry seasons when the temperature has 'remained above normal conditions for juiv length of time, it is desirable that the public should be conversant with the habits of this insect. With a greater knowledge of the mosquito and its conditions of life, so will be associated a greater appreciation of the necessity of taking reasonabde precautions. We are indebted* to Mr W. K. Hounsell, of Devonport, who is at present temporarily residing in the district, for the following interesting article on the mosquito, its varieties and the habits .of the species:— The work being carried on by the Mosquito Research Committee is of far more importance than is generally realised by the general public. A great deal of information on the habits of mosquitoes in this country has been collected and as a result it may safely be said that mosquito control should be strictly carried out. The Native Varieties. While our native varieties arc, as far -as'we know, unable to carry disease, we Lave in various parts of the North Auekla?".d Peninsula several varieties from tropical districts, ■ including one common to Queensland and the Islands, which is believed .to carry dengue fever and possibly elephantiasis. This mosquito is' closely related to the variety kiuwa to carry "yellow fever"' in America. It is significant thr.t all the introduced vaiietics have boon found in places visited by whalers and overseas vessels. Again in Australia it has been found that tropical varieties tend to spread into more temperate zones. Dangerous species previously only found in Northern Queensland have been located breeding freely in New South Wales. The recent discovery of a malariacarrying variety on a vessel arriving in Auckland shows that it is quite possible for a serious menace to our health to become established if precautionary measures are not taken. Department of Health Active. Fortunately the Department of Health is fully alive to the possibilities of this, hence the efforts which are being made to clean up breeding grounds in all parts of the country. The department however can do little, if the public remain inactive. It behoves each one of us to assist in the campaign which is being carried out. I shall deal more fully with this under the heading of control Life History. The female mosquito lays a .raft of two hundred or more eggs on suitable stagnant water. After a day or so these hatch out'into tiny "wrigglers" or larvae which live in the water eat-

ing microscopic organic matter. They musty however, come to the surface to breathe which they do by pushing the syphon, or breathing tube, above the surfaee of the water. The larvae gradually increase in size until they become* the "wrigglers" commonly seen in tank water during dry periods, or in any stagnant pool. They are remarkably hardy for they have been found in ruts on a road over which there was considerable motor traffic. Further, I have personally col'ected them on a i totball field a few minutes after the end of two games. .'M'ter some time the larvae change to tho third or pupae stage in which they Tremble commas, having a compara--1 i v cly large head with a small tail. They remain in this condition for a day or two and then the skin splits down the back and the adult insect emerges. Tlie whole period from the laying of the egg to the "emergence of the adult averages about 14 days. It may be less or considerably- longer, depending

on the temperature and the amount of food available. "

Assuming that each female f mosquito lays two hundred and forty eggs, and that half of these Will be females:, it is possible for one mjosquiito to hare 28,000 grandchildren in twenty-eight days. Before the female mosquito can lay fertile eggs she must feed on some warm-blooded animal. We are all apt to forget that this includes stock animals, and birds, besides human beings. At Mercer the attacks of mosquitoes made milking a difficult -task through attacking cows. I have seen a hogget so badly bitten about the cars that it was unable to move them. Mr Graham, the Mosquito Research Officer, reports having seen mosquitoes attacking fowls. In some North Auckland areas farmers winter their cows in bush area. They have no need to muster them, as with the advent of warmer weather the mosquitoes drive the cattle out when they can ea§ily be collected on the outskirts of the bush. Control.

Control methods may be divided into two groups. (1) The destruction of likely breeding places. (2) The encouragement of natural enemies.

The' fact that mosquitoes can only breed in stagnant water makes control comparatively easy. All tins, broken crockery, and bottles, old boots, etc., should be buried or covered up to that they cannot hold water Swampy places should be drained. Water tanks should be covered and house gutters (a fruitful source of the pest) kept cleaned and free from pools. In fact everything should be done to keep the surroundings of houses reasonably tidy and.clean. This not only controls mosquitoes, but also keeps down flics and vermin of various kinds. Dirty heaps of refuse are always a much more common source of mosquitoes than large lakes or ponds. In the event of mosquitoes being found in lakes and ponds these may be oiled with kerosene or, better still, a mixture of kerosene and castor oil. Control in Large Areas.

The encouragement of natural enemies concerns more the control in large areas of water. The chief enemies of the pest are frogs, fish, water Beetles and waterbcatmen and dragonflies. Those feed on the larval forms in the water. Birds and dragonflies also attack the adult insects in the air. In a certain area in the North the introduc/;'or. vf Irogs reduced the pest very considejably. The two varieties of native trout feed largely on mosquitoes, while the Department of Health is at present introducing small varieties of fish to help control the pest.

Water beetles and waterboatm.cn, two insects common in all ponds and lakes, do remarkably good work in eating the "wrigglers." These insects are exceptionally common in the Cambridge Domain lake and their presence contributes to keeping the pest down. It cannot, however, be too much impressed oi the public, that the chief breeding grounds are to be found around the household refuse heaps.