THE MOSQUITO PEST.

New Zealand Herald, Volume LXII, Issue 19177, 17 November 1925, Page 12

THE MOSQUITO PEST.

NEED FOR EXTERMINATION. METHODS OF PREVENTION. SOME SEASONABLE HIiNTS. In gpite of all that has -been said on the coittrarj, the stuaraet. months are now rapidly approachiflg, bearing with them their usual train of delights which will help to efface from the minds of Aueklanden the' memory ; of a particularly bleak, cold and wet winter. They will have their set-backs, too, and one of the chief of (hese will soon be heralded in the evenings by that persistent and wellknown buzz that proclaims the arrival of the mosquito.

This srnaii insect is an annual source of trouble, and of late years has assumed the dimensions of a pest. Though the mosquito that has Auckland for its habitat, is not so dangerous as his fellow ia the East, Africa or Central America, he is nevertheless an unwelcome visitor. The tropica! species are carriers of that j dread disease, malaria, and though our j own variety have not yet become as j dangerous as that, there have been many I cases of blood-poisoning from mosquito j bites, and there is also the possibility ] that the malaria germ may be introduced jat any time. Apart from this, tho mos- | quito is such a general nuisance that steps | should be taken to exterminate it. The I old adage that prevention is better than j cure will be found the best means of j accomplishing this end. j Mosqaitcs hare four stages of developj ment—the egg, larva, pupa and the 1 winged insect. The eggs are laid upon i water on which they float. After about |24 to 43 hours the ends open and the larvae escape. These are the familiar i "wrigglers" of pools and water barrels, j and are found in almost any standing | water. • They remain in this state from i one to three weeks, when the larva splits its akin and the pupa escapes.' This ; corresponds to the chrysalis stage of the ; butterfly. It then only requires a few } days of warm weather for the pupa to ; burst and for the adult insect to appear with wings ready to fly and, in the case I of the female, with the ability, to bite j and lay more eggs. . j The eggs are deposited chiefly in slowly ; flowing water, but have even been laid in cess-pools, brewery drains and stableyard pools. Large swamps are particularly favourable for breeding. Local Breeding Places. Natural breeding places abound in the vicinity of Auckland. Cabbage Tree swamp and Penrose swamp both yield millions of mosquitoes annually. The marshy country surrounding St. John's Lake is also very favourable to breeding, while irt the heart of the city there are the Grafton and Grey Lynn gullies. Through both of these run small creeks, | and in the former case there is a considerable amount of hush and scrub which also helps the breeding of the insects. Both creeks form pools and bogs, and these, together with old tins that have been left lying about, are adI mirable places for the hatching of the

eggsThe same can be said of the Domain creek, which follows the railway line behind the well-populated suburb of Partial], and there are also small slow-Sowing creeks entering the harbour in the Hobson Bay and Ponsonby areas. In the Western Springs lake itself there are practically no eggs laid, but Cox's Creek just beyond it breeds large numbers. These are the places from which most of the Auckland mosquitoes come, hut the .small pools of stagnant water which lie in backyards also contain eggs and thus add to the number of the insects. Things That Should Se Done. It can be seen therefore, that the problem of extermination is a very difficult one. The only method' is to prevent the insect from reaching the adult stage, as the popular summer evening pastime of "swatting" can only account for a very small number. It is fairly simple to stop mosquitoes from breeding in the small pools. No pools of rain water should be allowed to remain, and any backyard or stable refuse which could contain water should be emptied and filled with earth. Old tins should always be crushed Hat and all bottles broken before they are disposed of at the refuse tip. Lily ponds and fountain pools should.if possible, be abolished. If not the margins should be cemented or carefully gravelled and green slims regularly cleaned off as it collects. Where tanks, cisterns or wells are necessary to supply water the openings should be closely covered with wire gauze, galvanised to prevent rusting and with 16 to IS meshes to the inch. Care should be taken that not the smallest aperture is left.

When neither drainage or covering is practicable, the surface of the standing water should be covered with a film of kerosene which chokes or kills the larvae. The oil may be poured from a can or sprinkler, or a drop-barrel may be used. It will spread itself, and one ounce of oil is sufficient to cover about 15 square feet of water. This should be renewed once a week.

Mosquitoes frequently breed in the house, particularly in flower vases, tubs and other vessels. These should he emptied at least twice a week and rinsed carefully to make sure that no eggs are left along the edges. Gully traps of drains should be flushed frequently. Value of Top-Minnov/s,

It can easily be seen that none of these methods are applicable to the large tracts of water where the mosquitoes breed in large numbers, with the exception of drainage. This is really the best method, but there are frequently many difficulties in the way before it can be carried oat. The spreading of kerosene would prove satisfactory, but a large quantity would have to be used. Pending drainage, the method that will give the best results is to stock the water with top-minnows. These are a small fish, a few years ago considered useless. It has now been discovered that they have an immense appetite for mosquitoes in any form and they propognte very rapidly. The Vislaia Delta in California was a favourite breeding ground for mosquitoes. Last May, however, a few hundred tiny minnows were liberated in various places where mosquitoes abounded. It has been stated that now one could.spend hours along this series of pones where ones mosquitoes swarmed and never feel a bite or hear k buzz from one of the insects. The army of minnows which is waging relentless war against the insects, now numbers over ten thousand. 'Hiis scheme could be adopted with advantage in many of the breeding places around Auckland. It must be emphasised that not too much care can be paid to the extermination of mosquitoes from small stagnant pools in private property. This calls for action by . the individual, while the, ridding of the pest from the larger bodies of water calls for corporate action.