154 NATURAL HISTORY OF ARTHROPODS. 



northern Europe, especially Lapland. In Cloe there are sometimes but two wings, 

 the hinder pair wanting ; while the species of Coenis never have any hind wings. 

 The most abnormal ephemerid is Oligoneuria, in which the wing-veins are very few, 

 and far apart, and the legs are imperfectly developed, and there are three caudal 

 threads. Allied to this is a Cuban form, Lachlania abnormis, in which there are 

 but two caudal threads. 



A. S. PACKARD, JR. 



FIG. 225. Psocus. 



