THE CANADIAN ENTOMOLOGIST. 227 



emerging from the pupte, which floated up against the edges of the basins 

 and pools. The larva was also abundant in the geyserite precipitate that 

 forms a flocculent mud in all these tepid basins. I soon found that this 

 mud is ahve with insects, chiefly Diptera, but there is a very large and 

 white Ochthebius and its larva, and also a common Philhydrns. The 

 latter lives only in the tepid pools, while the Ochthebius inhabits water 

 that is very much warmer. I regret that I had not a thermometer 

 with me to test the temperature. There is, of course, a little Salda run- 

 ning about the edges, and this seems to stand any amount of heat, as I 

 find it about the edges of springs which are actually boiling. But the 

 most curious thing of all is the presence of two species of Nebria — one of 

 large size, with yellow legs ; the other smaller, and entirely black, living 

 under pieces of geyserite about the hot springs, and even on the sides of 

 the cones of the largest spouting geysers, where they are liable to be 

 washed away in a flood of boiling water. The larvae of these JVebrias 

 live also in the sulphurous geyserite sand near the hot springs and geysers, 

 but not so near to the geyser vents as the imagos. There is, however, a 

 large Bembidium, with variegated elytra, which is always found under bits 

 of geyserite and in the geyserite sand about every hot spring and geyser ; 

 its larva lives with it in the same places. 



In the Firehole River, just below the Excelsior geyser, which contin- 

 uously pours rivers of boiling water into the stream and raises its tem- 

 perature to probably 70*^ or 75" F., there lives an Elmis of medium size ; 

 but I found it rare and had not time to collect it in any numbers. In 

 a small stream of tepid water, running through a grassy plain, I found 

 that same slender, undescribed Elmis which we took below the old 

 powder mill in Ogden Canon. It swarmed in this stream in countless 

 millions, every stone and stick was alive with it and its larva. There was 

 also a Corixa, apparently the same species I took in Utah Lake. Here 

 it swarms in incredible numbers, forming black masses all along the sides 

 of the stream. Of course the stream was sulphurous and heavily charged 

 with mineral matter, so that sticks, moss and everything that fell into 

 the water was soon silicified or coated. All the stones and sticks in the 

 bottom were streaming with peculiar algae of various colours. In the 

 Firehole River, above the upper geysers, where it is an ordinary mountain 

 stream and quite cool, I found in debris in the water a marvellous Elmis 

 with red spots ; but four times larger than the largest I ever saw. In the 

 same debris were peculiar aquatic larvae, apparently Coleopterous, and 



