PESTS—NOT PETS

Evening Star, Issue 20374, 4 January 1930, Page 10

PESTS—NOT PETS

MENACE FROM MOSftUITOES eradication a community duty EXPERT IN SEARCH OF DUNEDIN SPECIES “ Mosquitoes are pests —not pets.” Although Mr David H. Graham, who was for three years research officer or the Mosquito Research Committee in Auckland, has not seen any of the troublesome insects in. Dunedin, ho issues a warning to the people hero to treat the' mosquitoes as unnecessary pests, and not as pets. By allowing water to lie about in' pools and in empty tins and tyres and other receptacles, the public at large cultivates, the mosquito as a pet. “ I have not seen a mosquito yet in Dundein,” said Mr Graham to a ‘ Star ’ reporter at the Portobello Marine Research Station yesterday. Mr Graham is now in charge of the biological work at Portobello, and he said he would be very pleased if people who caught mosquitoes would send them to him. Specimens in either the larva or adult stage are sought after by Mr Graham, who anticipates that he will be able to study the mosquito problem in tho spare time from the station. P'eople often complain of being bitten by mosquitoes in- Otago, and Mr Graham is particularly interested in the discovery of' the various specimens. For over ninety hours a week for three years Mr Graham studied the mosquitoes of the Auckland district, and he discovered ten specimens, and traced their life history. The mosquito menace is a serious one, and on two boats from the East—the Sussex and the Narbada—Mr Graham found malarial mosquitoes. It was easy for the disease-carrying.pests to fly out of the cabins and holds ,of the Eastern vessels, said Mr Graham, and the first step to prevent disease was ,to remove the cause. To rid NewqZealaud of mosquitoes would be a simplei matter, although not necessarily easy. It everybody worked a little the country would soon be freed of_ them.. . The general problem of mosquito control was solved long ago, and his investigations in vaxi-, ous parts of the dominion into the' breeding and life habits of the pests showed now the control could be exercised. .

• “Wo call the mosquito a nuisance because it bites, but perhaps we dislike it chiefly because it keeps us 'awake at night by its .persistent singing. But But it is more than a nuisance.■ . It is a real danger to health, for apart from loss of rest many people suffer severe pain and serious illness from the effects of mosquito bites. Wo have at,'least ten species of mosquitoes breeding inNew Zealand. The total number of distinct species in the world is over 1,400, and many more new ones are still being found. Of the New Zealand ones some are essentially household or domestic pests.” . Mr Graham has found that some of the New Zealand mosquitoes live in fields near drains or in swamps. Other kinds are found only in the bush, and at least two varieties only frequented the seashore. Three varieties he found infested the houses and habitations, only two of , which were troublesome in the country. One bit at nights only, another, confined to the city, bit only by day, but the third, which lived in the country, made up for it by biting both day and night. ;[t was a much smaller specimen than the other, two., . .

From the tenement owner to the Government Mr Graham traced the responsibility “of the people for their oto mosquito troubles. In the water left in a kerosene or petrol tin 2,000 to 3,000 mosquitoes would breed every three weeks, while 250 mosquitoes. would be bred m a jam tin in the same period. Every tin in a garden ,or yard was . a potential source ,of disease . and nuisance. In industrial _ Auckland he had found very few premises, or even warehouses, where backyards were quite clear of. water holding, k and therefore mosquito-breeding rubbish. , But the premises of private individuals were not. the only offenders., . The areas; under the control of the Government, local bodies,, and harbour boards, such;, as dumps, required very careful observation. Country residents, with their rain water tanks and troughs and unattended pools in the fields, helped themosquito to breed in. enormous numbers.

“When one realises that a jam .or milk tin or disinfected bottle holding a few ounces of water will breed hundreds of mosquitoes every three weeks and >an unattended; petrol tin with a gallon of water breeds thousands in the same time, it behoves us all to do our little bit,’’ said Mr Graham. “If every owner of a back yard or vacant section, each foreman of . in-, dustrial and commercial houses, each local body inspector or officer responsible for harbour board and, government areas did his small share in destroying these unnecessary waterholding containers or in treating those which cannot be destroyed with oil or disinfectant, 95 . per cent, of these mosquitoes would disappear. And there would also bo less harbourage for rats.” The bite from the mosquito was really a pricking by a set of fine needles or lances, carried in the proboscis or sheath projecting from the head. It was the female that bit and she bit in order to get human or animal'blood, which seemed to be necessary before she could lay eggs. Mosquitoes must have water for breeding and development of tbe early stages. The eggs were laid on the water and from these eggs hatches out the larva or wriggler. Although it lived in water, the wriggler breathed air, for which purpose it had a longish tube or siphon, which looked very much like a tail. The wriggler was the feeding and growing stage. Then followed a resting stage called the pupa, in which the legs, wings, and other parts of the adult were formed. The pupa finally came to the surface, the skm opened along the back and, the full grown mosquito climbs out into the open air . and whirred away on his .pestering life. To keep mosquitoes away, Mr Graham recommended oil of citronella, but for bites, he said ordinary. soap could be used. The preventative was of little use. The cause should be removed. He had known women to be paralysed in the legs by being bitten while sitting on porches in, Auckland, and intense pain had been caused thousands. of other people. Stock of all descriptions were also troubled by the posts in the Far North. Ah ounce of kerosene on 15 square feet of water would kill all the larva. Tanks were the principal breeding places in the country, and he recommended that olive oil should bo sprinkled in a film over the tanks after every rainfall. Olive oil would not taint the water, but once the surface was broken a fresh issue of oil would have to be applied. Discussing the malarial mbsqqitoes found on the Eastern boats, Mr Graham said he did not think they would live in Otago owing to the colder weather. Mr Graham has already issued one scientific paper on mosquitoes of Auckland for the New Zealand Institute, and he has a paper covering four species ready; for |he publishers..