SOME AQUATIC INSECTS 99 



an extremely delicate pellicle, hiding the true 

 colours of the perfect insect. This sub-imago, 

 as it is called, attaches itself to any convenient 

 resting-place near the pond or stream, and then, 

 after a short interval that varies slightly in its 

 duration in the different species, the delicate 

 outer skin is ruptured and the perfect insect 

 emerges, with brighter wings and longer caudal 

 bristles, and flies away to spend the brief period 

 of its perfect existence in courtship and merry 

 dancing. 



A small, rather compactly built Spider, about 

 half an inch long, and of a deep ashen colour, 

 may frequently be seen running in sudden swift 

 spurts over the floating leaves of the water 

 plants. Its body is densely clothed with fine 

 hairs, the use of which are immediately realized 

 when the Spider dives into the water ; for they 

 carry down a supply of air in. their interstices, 

 and so enable the Spider to breathe while under 

 water. When the Water-Spider's body is sub- 

 merged, this coating of hair gives it a very beauti- 

 ful appearance, as if it were partially coated with 

 burnished silver. The Water-Spider is a most 

 interesting creature in its habits, and may be 

 kept under observation very easily in an 

 aquarium containing growing water plants and 

 a few small aquatic larvae, etc. It will then be 

 seen that the Water-Spider not only spends the 

 greater part of its life beneath the surface of the 

 water, but that it pursues its prey and constructs 

 its nest therein. The Water-Spider builds itself 

 a dome-shaped nest, attached by a series of 

 silken threads to the surrounding stems of the 



