SAND-FLY PEST

Hokitika Guardian, 28 November 1930, Page 5

SAND-FLY PEST

ERADICATION METHOD,

INTRODUCTION OF AUSTRALIAN DRAGON-FLY.

If experiments now being conducted by 1 the Department of Scientific and Industrial Research through Professor E, Peroival (Professor of Biology at Canterbury College) nre in two or three years’ time proved successful, New Zealand may one day . be permanently rid o<f the sand-fly peßt. By the liberation of a certain specie’s of Australian dragonfly at the Cawthron Institute-and the Class Mountain Biological Station, it is hoped ultimately-to eradicate ..sandflies from the neighbouring areas and so to justify a wider application .of. this unique treatment. ‘ Professor Percival explained at Christchurch' that a species of a drag-on-fly was found in Australia in a stream in which, although all conditions were favourable no sand-fly larvae were to be found. Conversely, when the species ' was absent, the sand-fly larvae were common. It lished in the laboratory that this drag-on-fly ate the larvae of the sand-fly, the conclusion being that, the scarcity or absence of sand-flies in any stream was due to the presence of these drag-on-lles.

INTRODUCTION: IN NEW ZEALAND.

It was suggested that the species might usefully be introduced into New Zealand, and two consignments were received. 0 fthe first, there was only a single survivor; but of the second, about 25. dragon-flies were still alive, and these were divided between the Cawthron Institute an dthe Cass Mountain Biological Station, from both of which they were liberated in neighbouring streams.;. . - “Nothing of the result' of the experiment can be know'll until we find opt. whether the inseotß can be recovered and whether they are increasing,” said Professor Percival. “They cannot produce any effect for a very long time until they become sufficiently numerbu to reduce materially the number of sand-fly larvae. They were simply pul into the streams and left to fend for themselves. My hope is that one batch of eggß will be laid this year. If that happens, the species will be fixed and will .spread, possibly, in about a century, covering the whole of the South Island,” • '

SAND-FLY LARVAE UNDER WATER.

It was not. generally recognised, he added, that the larvae of the sand-fly were usually found in running watei. The pupae usually fastened on to stones in the bed of the stream, and the insects came to the surface in bubbles of gas. They might thus be carried hal a mile downstream before they reached the surface and were liberated into the air. One fact that militated against the success of the treatment was that the sandrfly could do with different aquatic conditions from the dragon-fly.