ANURIDA. 415 



Fam. I . , Eu'tomobryidse . — Scales present 

 or absent. Springing organ well developed. Isotoma, 

 Entomobrya, Orchesella, Lepidocyrtus, Acted etes, Bechia, 

 &c. 



Fam. II., Achorutidse . — Scales never present. 

 Springing organ greatly reduced or absent. Podura, 

 Aehorutes, Anurida, Xenylla, Aphorura, Neanura, &c. 



Sub-Order II. — Symphypleona. 



Body sub-globular, the abdominal segments more or 

 less fused together. Yesicles of the ventral tube long and 

 tubular or short and sac-like. 



Fam. III., Sminthuridse . — With the 

 characters of the sub-order. Sminthurus, Sminthurides, 

 Papirius, Neelus (Megalothorax). 



These insects are found in a great variety of situa- 

 tions ; they occur among dead and decaying vegetable 

 matter of all kinds, they may be found among moss, 

 under the bark of trees, and can be obtained from road- 

 side herbage of almost every description. They are 

 plentiful on the borders of ponds and streams, and are 

 also to be met with on the surface of the water itself ; some 

 few species inhabit the sea-shore and others are to be 

 found on the surface of the snow and glaciers. The only 

 condition which seems essential for their welfare is that 

 considerable amount of moisture is present, for they seem 

 incapable of surviving in very dry situations. 



The order is practically world-wide in its distribution, 

 and it is remarkable also on account of the extremely 

 wide distribution enjoyed by many of its individual 

 genera and species. The genus Isotoma, for instance, 

 seems almost cosmopolitan, it being known from both 

 Arctic and Antarctic regions, and is distributed through- 

 out Europe and many parts of North America. It has 



