GIVE US BLOOD! IS MOSQUITO'S CRY.

Star (Christchurch), Issue 18985, 3 February 1930, Page 3

GIVE US BLOOD! IS MOSQUITO'S CRY.

NO POOL TOO SMALL TO ACT AS NURSERY. (Contributed bv the Department of Health.) Mosquitoes besides being in some instances the means of conveying disease from one human being to another cause great annoyance by their bites. Measures for their suppression are therefore well justified. 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.”

Life History. There 2re 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 mosquito is “ give us blood.” Before it can lay eggs 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 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 comma-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 her salivary glands through a tube-like arrangement. In this fluid are sometimes the organisms which produce malaria To quote Shipley: “ Down this minute microscopic groove has flowed the fluid which has closed the continent of Africa for countless centuries to civilisation, and ■which has played a dominating part in destroying the civilisation of ancient Greece and Rome.”

Breeding-Places. 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 estu aries: in fact anywhere where water is allowed to stand.

In New Zealand the larvae have been found in rain water, in holes in the

trunks of trees, and dead tree-ferns, and at the bases of the leaves of broadleaf plants; in crevasses and depressions of volcanic areas, and along the coastline in semi-saline or brackish pools of water. Large sheets of water, lagoons, and rivers are unsuitable although they .may be found in adjoining potholes and puddles.

A certain number of adults survive the winter. In Auckland city adults, larvae and pupae have been found in wet cellars in mid-winter. Bushes, etc., afford shelter but not breeding grounds. Preventive And Control Measures. 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. Cert.ain 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. Dragon-flies and water beetles are also very useful. 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 drain pipes. 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 tea spoonful to the gallon of water or enough to make the water milky when stirred. (2) Coal tar 1 pint; turpentine 1 pint; soft soap loz., water to make up to two gallons. This will treat three hundred gallons of water. (3) Add copper sulphate to the water to be treated in the proportion of one part to five thousand of water.

Stored -water supplies may -be screened (18 meshes to the inch) closed in, or a layer of sawdust spread upon the surAgainst the egg stage “ race suicide ” measures may be used. Hang cigarette tins half-filled with water,, or. better still, hay infusion, under the branches of trees. The eggs are laid in these. Empty the tins every forty-eight hours into a saucepan and boil the water to destroy the eggs. The adult mosquito dislikes smoke—flat cakes of dried cowdung sprinkled with pvrethrum powder, and then burnt may be tried. The burning of pvrethrum powder alone, 31b per 1000 cubic feet in a closed room, is useful This stupifies the insects, which must be swept up and burnt. Citronella oil will protect the face and hands to some extent. If this stairts the clothes; the stain can be removed by oil of turpentine. Healthy sites for houses should be chosen to the windward of swamps etc. and as high as possible. Friar’s balsam allays bites. Remember, however. the slogan: ‘‘No water, no mosquitoes.”