The larvae of this Chironomus are lovers of swift rushing water, 

 and from the very nature of their habits it is impossible for them to 

 thrive, unless the water, passing swiftly by the nets they spread out on 

 the arms surrounding their tubes, conveys thither suspended matter for 

 them to feed upon. In consequence of this, larvae that are kept in 

 vessels of still water soon languish and die, without performing their 

 characteristic actions. It is therefore absolutely necessary that the water 

 be kept in constant motion by some mechanical means. 



The somewhat crude, though effectual, method that I have used to 

 overcome this difficulty is as follows : Across the top of an enamel 

 dish, containing larvae, water and mud, I placed a strip of wood a few 

 inches wide on which was fixed a clock-work paddle. This was made 

 from a cheap day-clock with second hand. The escapement wheel was 

 removed and in its place was put the second hand wheel. To the 

 projecting part of the axle was attached a glass paddle. The clock 

 when wound up was found to keep the paddle in motion for about ten 

 hours, and I found it sufficient to wind up the clock morning and 

 evening, as an hour or two in still water did not seem to injure the 

 larvae (fig. 40). 



THE EGG. 



The female fly lays about ninety eggs enclosed in a spherical The Egg-mass. 

 gelatinous envelope. These egg-masses are attached to the moss 

 covering the boulders and stones of the streams which the flies 

 frequent. They are generally found just below the surface of 

 the water, sometimes a few centimeters down ; but this must be 

 because the river has risen since they were deposited, for it seems 

 almost incredible that a fly so small and fragile could climb down 

 so far in such turbulent water. A fly reared in captivity deposited 

 its eggs at the surface of the water, and this no doubt is the usual 

 proceeding. The egg-masses are not easy to find, and it was not 

 until the second year that I obtained any for examination. Fine hot 

 weather in June is the best time, for then the river is full of the 

 cases of full grown larvae and pupae, and the flies are coming out 

 daily. 



