29 



each femur and tibia, a pale mid-dorsal abdominal line, and the 

 apical margins and hind angles of abdominal segments and the 

 tips of abdominal appendages also pale. 



The imagos are like the Libellididie in the great develop- 

 ment of the eyes, which touch for some distance along the 

 middle of the head, and in the presence of a roughened carina 

 on the sides of the abdominal segments. The nearness of the 

 lowest forms of this family and the LiheUi(H(l((' in wing vena- 

 tion and nymphal sculpture is evident ; but the jEschnidce as a 

 whole are much nearer the primitive stock by reason of several 

 characters, especially the structure of the labium and gizzard, the 

 general form of the nymph, the form of the egg, and the manner 

 of oviposition. The wing triangles are elongate lengthwise of 

 the wing, as in the Gotnphidw, usually with several cross-veins; 

 most of the antecubitals not coincident. The female is provided 

 with an ovipositor, by means of which the elongate cylindrical 

 eggs are inserted into various plants and substances in the water 

 instead of being washed off by dipping the abdomen during 

 flight as are the more or less oval eggs of the other Anisoptera. 

 Even in the nymphs the developing ovipositor, on the eighth 

 ventral abdominal segment, is well marked and recognizable in 

 all but very young individuals. In the males the corresponding 

 parts are more difhcult to see, but this sex possesses a very 

 evident scale-like piece overlying the base of the superior ter- 

 minal appendage. 



Mr. Needham has observed that the eggs are deposited in 

 the stems of plants, in floating timbers, in piers, etc., at or very 

 near the surface of the water, either above or below it, but 

 always in moist tissue. He has floated pieces of decaying wood 

 upon a pond as a means of obtaining Beschnid eggs, and these 

 proved very attractive to the ovipositing females. 



' The usefulness of the imagos, especially Anax Junius, on 

 account of the enormous quantities of pestiferous gnats and 

 mosquitoes which they destroy, puts them among the particular 

 friends of mankind. 



