MOSQUITO CONTROL

Wanganui Chronicle, Volume 76, Issue 299, 19 December 1933, Page 9

MOSQUITO CONTROL

METHODS IN DOMINION ARTIFICIAL AND NATURAL EXPERIMENTS WITH FISH Efforts that were being made in New Zealand to control the mosquito pest by both artificial and natural means were described to the Wellington Rotary Club luncheon by Mr. W. J. Phi Hipps, of the Dominion Museum staff. The problem was particularly to the fore this summer, he said owing to the mild winter, which had been responsible for an increase in the numbers of all sorts of insects. Recently he had been travelling about the country in order to find scientific ways of controlling the pest in different parts. Unfortunately the problems presented were not at all the same. Mosquitoes were to be found breeding in pot-holes left by the hooves of cows, in deep, grass-covered ditches, swamps, roof gutters, tanks and even in pockets of water in the trunks and forks of trees. Mosquitoes laid their eggs in these places usually at some time between midnight and six o’clock in the morning. Two or three hundred eggs were liad at a time, and those hatched in about' throe days, although they might, be delayed by colder temperatures, in eight to 14 days the larvae had become pupae, which shortly after loft the water. In this way the female mosquito could in about a fortnight be the mother of over 200 adult young Both tho larvae and the pupae came to the surface of their breeding water every now and again to take air, and it was this habit that had first sug gested the means of control used in ‘constructing the Panama Canal —of putting a thin coating of oil over the water. Tho breathing tube in the in. sect’s tail was unable to break the surface, and tho mosquito suffocated in about an hour. Tn one place in tho Wellington dis- ■ trict this method was at the present time being used, with kerosene tins, dripping oil on the water dav and night. However, this method of control was not always adequate or de- ■ sirable. Apart from the fact tb.? v there was a possibility of it affecting i drinking water, no life could 'continue to live under the. oil surface, and if ’ (he method were used on a large scale ’ bird lifo might be affected by a, short age of insect food. Steps were now being taken in New : Zealand for scientific control of the pest, by tho application of natural I means, Mr. Phillipps continued. The

methods known to the world were the introduction to the affected waters of certain kinds of fish, birds and »water snakes. Some years age ho had imported from Hawaii a few small fish known as top-minnows. These fish multiplied and spread with remarkable rapidly, and therefore he was being very careful with their use, and none were to be liberated until further experiments had been made with them. Top-minnows had been exported to almost every country in the world to clean up tho pest. Their use was one of the greatest fish romances in the world, as in European countries, as far as the Balkans and Russia, they had made very large tracts of land habitable. Unfortunately it had been found that the fish not only eat the mosquitoes but other native material as well, and their use was now being controlled as much as possible. A species of fish related to whitebait and also tho mud-fish were being experimented with in New Zealand. For tho Control of the sandfly larvae, which bred in running streams, he was experimenting with the introduction of carp. “We are lucky in not having any malaria-carrying mosquitoes in this country, ami it would be a tragedy for New Zealand if they were ever to spread hero after the fashion of the white butterfly,” said Mr. Phillipps. “In some cases conditions are favourable for them hero. Throe species of them have been found in tho South of England, and there have actually been some small malaria epidemics there. “We in New Zealand should see to it that we control as much as possible of tho water areas so that, they cannot get a footing. The direct steamer route from Panama, offers opportunities for them to get. here, and when over-sens air travel comes we will also have to watch that very closely.”