140 Annals Entomological Society of America [Vol. XIII, 



Embiidijta. Living under damp stones and wood on the 

 ground, nests of ants or termites, in small colonies but not 

 forming societies; the nymphs constructing passages lined with 

 a silk-like secretion from glands in the maxillae; partly carniv- 

 orous, partly phytophagous; nymphs very similar to adults. 

 Tropical or sub-tropical. 



Corrodeyitia. On bark, under logs, old books, etc., feeding on 

 animal and vegetable refuse, mouldy substances, etc. Eggs laid 

 in patches or clusters under bark, or in other protected places, 

 covered with a web; incubation period generally during winter 

 in temperate climates. Period of growth probably short, there 

 being sometimes two or perhaps three broods. Number of 

 moults said to be four in Psocus. Nymphs resembling adults 

 but without ocelli, which are present in the adults of winged 

 species. 



Mallophaga. Epizoic on birds and mammals, feeding on 

 feathers, epidermal debris, etc. ; eggs glued singly to hairs or 

 feathers in the area inhabited by the insect, sometimes localized 

 in groups common to many individuals. Incubation period not 

 known definitely for any species, probably long; number of 

 moults also unknown, apparently few. Length of life probably 

 several months in most cases. 



In Group 2 the nymphs, or naiads, differ from the adults 

 more widely than in group 1 in correlation with the greater 

 difference in environment. The period of growth is usually 

 longer, being frequently three years, and the number of moults 

 greater. Length of life cycle is to some extent proportional to 

 size attained. 



Plecoptera. The stone-flies show least divergence between 

 larval and adult structure. The adults are feeble insects of 

 secretive habits, serving only for the function of reproduction. 

 Eggs small, carried by the female for a time in a mass at the 

 genital orifice, and finally dropped freely into the water. Naiads 

 inhabit well aerated water, clinging to undersides of stones, to 

 which habitat they are adapted by the possession of filamentous 

 tracheal gills, chiefly thoracic, and by their flattened form and 

 legs, the latter fringed with swimming hairs. Food of naiads 

 smaller aquatic animals. Length of life probably one to three 

 years; number of moults not known for any species, probably 

 very variable. Adults appear usually early, sometimes emerging 

 on ice and snow, the order having on the whole a remarkable 

 power of withstanding cold. 



