nished with strong mandibles, and two eyes. 

 The feet are six in number, and are not natatory, 

 the anterior pair being shorter and thicker than 

 the others, which are considerably elongated, 

 and not dilated, nor deeply ciliated. Thus consti- 

 tuted, the animal crawls at the bottom of the 

 water, with the feet and the anterior part of 

 the body protruded from the tube, in search of 

 food. 



When about to undergo the change into the 

 nymph state, the larva affixes its tube to some 

 permanent object. It then proceeds to close the 

 ends of its dwelling by a silky net, the meshes 

 of which are so small as to prevent the ingress 

 of depredating insects, and yet sufficiently large 

 to admit of a free circulation of water for the 

 purpose of respiration. The head of the nymph 

 is provided with a kind of beak, consisting of 

 two hooks, which are used to force a passage 

 through the net-work. At this period, which 

 occurs in fifteen or twenty days after the change 

 from the larva state, its period of immobility 

 ceases: it departs from its tube, and walks or 

 swims with activity, the feet being fringed for 

 the latter purpose. The young animal now for 

 the first time emerges from the water, and seeks 

 a dry, secure position for its ultimate change 



PLATE 44. H 



