Health Notes

Sun (Auckland), Volume I, Issue 238, 28 December 1927, Page 7

Health Notes

MOSQUITOES LIFE CONTROL (Contx’ibuted by the Department of Health.) Mosquitoes inhabit every country in the world —from the barren polar circle to the coral strands of India. The mosquito is an unusually beautiful insect. This fact, however, has been concealed from the public, partly owing to the diminutive size of the insects, and more especially because of their irritating bite which causes the victims to kill at sight, rather than examine their ethereal beauty or their fascinating evolutions in the air. For centuries it has been rc-.lised that the most serious difficulties in the development of the tropics are the diseases peculiar thereto. .Not till early in the present century was it shown that mosquitoes are the means of the spread of certain of these serious ills. Of these it is definitely proved that malaria and dengue fever are carried by certain mosquitoes. The story of the Panama Canal is the conquest of the mosquito. In Palestine also, thanks largely to the anti-malaria work of the medical corps, Allenby was victorious; other campaigns, as that under Napoleon and in early periods, had failed, because malaria had so ravished the troops that the army could not hold on all the year round and had to retire before the warm season. The yellow fever of South America is also mosquito borne. Doubt has existed as to the role of the mos--1 quito in the African type of yellow fever. In an attempt to solve the problem. Dr. Adrian Stokes, one of the most brilliant workers in medical science in this generation, recently lost his life from yellow fever in West Africa. It is thought that he probably became infected from the bite of one of his own experimentally infected mosquitoes. LIFE HISTORY New Zealand is indeed fortunate that these diseases are not prevalent here; the particular types of mosquito which convey these troubles have not been proved to exist in the Dominion. Nevertheless, mosquitoes are always nuisances, and the annoyance they cause is in itself sufficient reason for measures toward their suppression. Heavy as is the indictment against mosquitoes, there is perhaps one item on the credit side—it is said of one species of the family that its fondness for the naked knees of the Highlander has given us the “Highland Fling.” There are. four distinct stages—(l) The female lays one hundred or more eggs in one batch, the eggs are minute, blackish bodies usually laid on the surface of still or stagnant water. The common rain barrel type, and also many others, glue their eggs into rafts which look like flakes of soot. The | burden of the cry of the female mosj quito i?. Give us blood ” Before it can lay a meal of blood is a

necessity. (2) In one to three days the eggs hatch into larvae. These are the “wrigglers” from their habit of wriggling through the water with quick, jerky movements. They must keep coming to the surface to breathe. This is effected through a breathing tube located at the tail end. Their food consists of minute particles of vegetable or animal matter. (3). In about a week, if the weather is warm, the wriggler casts its skin and turns into a common-shaped body called the “pupa” or “nymph.” The pupa takes no food, but like the wriggler comes to the surface to breathe. Its breathing organs this time are situated close to the head. (4) After two to five more days the skins of the pupa split open and the winged mosquitoes emerge to the surface of the water and fly away. Male mosquitoes are vegetarians; it is only the female that bites. When she bites she injects into the victim a fluid from i r salivary glands through a tube-like arrangement. In this fluid are sometimes the organisms which produce malaria. To quote Shipley: “Down this minute miscroscopic groove has flowed the fluid which has closed the continent of Africa for countless centuries to civilisation, which has played a dominating part in destroying civilisation of Ancient Greece and Rome. No body of water is too small for a mosquito nursery. They breed in puddles by the roadside; in old tins, bottles, fire-buckets, choked roof gutters, flower-pots, tubs, etc., in cesspools, drainage sumps, swamps, pools, slow-flowing and weedy streams, river estuaries; in fact, anywhere where water is allowed to stand. PREVENTION AND CONTROL The control of the mosquito is largely the control of breeding places. The best results are obtained by communal efforts, but individual efforts are of great importance. Certain natural enemies are of service; fish are very effective. The margins of pools, streams, etc., should be kept free of vegetation to allow the fish access; ornamental ponds may be stocked with goldfish or minnows. Dragonflies and water beetles are also very useful. Anything which collects water should be dealt with. Old tins, bottles, etc., should be removed and buried; spouting must be cleared and receptacles emptied at least once a week and allowed to become quite dry before refilling. Much may be done by the draining and abolition of swamps, filling in of ponds and depressions, and the straightening and cleaning of streams and ditches, or by the use of drainpipes. Unnecessary scrub may be cleared, but is useless if water remains. Where water cannot be removed, such should be sprayed weekly with kerosene. The water must be covered with a complete layer of oil, two tablespoonfuls should cover fifteen square feet of surface. A good spray mixture is kerosene 60 parts fuel oil 40 parts These oil films kill the larvae by preventing breathing. The addition of a little castor-oil to the kerosene gives a better film. Wind is apt to destroy the film. The following larvicides are effective:—(l) Commercial cyllin 1 teaspoonful to the gallon of water or enough to make the water milky when stirred; (2) Coal tar 1 pint; turpentine 1 pint; softsoap, 1 oz.; water to make up to two gallons. This will treat Three hundred gallons of water. (?,) Add copper sulphate to the wafer to be treated in the proportion of one port to five thousand or watei