ioo NEW ZEALAND ENTOMOLOGY. 



commonly in the green, slimy weed floating in large 

 masses on all stagnant waters. Being very small it is 

 rather difficult to detect, and is best procured by washing 

 a small quantity of the weed in a saucer of water, when 

 the little insects will be at once seen walking about at the 

 bottom. On examination with the microscope the case will 

 first arrest attention, being of a most unique structure. Its 

 shape is best described as closely resembling that of a minute 

 pocket-flask, very much flattened at the lower end and 

 almost transparent. Its surface is slightly corrugated, and 

 the neck of the flask constructed of a much denser material 

 than the body. It is open at both ends, the posterior end 

 being perforated, by a long shallow slit, which extends for 

 nearly the whole width of the case, thus admitting a free 

 circulation of water round the larva, which is also able to 

 turn round and project its head and anterior segments 

 through the lower aperture, thus occupying the reverse 

 position to that shown in the illustration (Fig. 3a). It is,, 

 however, prevented from actually leaving the case by its 

 abdomen, which is too large to be withdrawn from either 

 end. The head and thorax of the larva are very horny in 

 comparison with those portions permanently retained in the 

 case, the legs being constructed to fold up into the smallest 

 possible compass, a cavity existing in each joint for the re- 

 ception of the preceding one a structure which is almost 

 universal among the caddis-worms. The two organs,, 

 situated on the posterior segments, are doubtless respira- 

 tory in their function, a large air-tube taking its rise from 

 each and ramifying through the body in all directions. 

 When alarmed these insects retreat into their cases with 

 lightning rapidity, remaining concealed until the danger is 

 passed. Their food probably consists of the green weed,, 

 although they are perhaps carnivorous, feeding on the 

 rotifers and other animalculae, which swarm in the water 

 where they are found. 



