PoYNTON. — Insect found in some Hot Springs at Taupo. 171 



cascades from the source of the largest springs to the bottom 

 where its waters flow into the creek. As the water spreads 

 out in several directions after issuing from the earth there are 

 different series of these basins, and altogether they would 

 cover about a quarter of an ctcre. Where there is water on 

 the rims it is quite shallow, but a considerable part of most of 

 them is exposed. A few inches from the edge the water 

 deepens to 6 in. or 8 in. Covering the bottoms of these pools 

 or basins, which vary in area from less than a square foot to 

 several square yards, there is a slimy vegetable growth of 

 dark-green colour of varying thickness. 



While on a visit to these springs last March I noticed great 

 numbers of small flies hovering about the pools or on the 

 silica at their edges. They were really in millions, some of 

 the dry patches of silica being covered by them 'to a depth of 

 an inch or more. Their size was about half that of the 

 common house-fly. In shape they were something similar, 

 but more slender and graceful, and of a dark colour, almost 

 black. 



Their power of flight was feeble. I asked a resident 

 of the locality if they appeared in the autumn only, but he 

 assured me that they were there all the year, and that in 

 the spring-time numbers of native birds gathered about the 

 springs to feed upon them. 



It occurred to me that they might breed in the hot water, 

 and so I examined the organic matter at the bottom of the 

 basins. It was alive with larvae about one-half as large as 

 that of the blow-fly, of a dark greyish-green colour, shaped 

 curiously like a shark with its double-lobed tail. In still 

 pools this slime could be seen all in motion, so numerous 

 were these larvae. The green matter was evidently their 

 food, and supported them generously, judging by their 

 numbers. On the surface of the water a great many pupa- 

 shells were floating. These shells drifted to the lips of the 

 basins, and in a great many places, becoming entangled, they 

 formed small obstructions across the little depressions through 

 which the water flowed. As silication proceeds rapidly in 

 most of these springs, it is obvious that these rafts of shells, 

 being cemented together and to the basin-edges by the silica, 

 will m time raise the level of the water, compelling it to 

 find an exit elsewhere, and this in turn will get blocked too. 

 This may afi'ord an explanation of the remarkably level nature 

 of the walls of these small i'eservoirs. I broke off a piece of 

 the top of one of these dams, and the outlines of numerous 

 shells imbedded in the silica were clearly visible. 



I regret very much that my visit, which was limited ta 

 about an hour, prevented me from making further observa- 

 tions. Some specimens of the fly were sent by Mr. Hudson 



