898 



AN INTRODUCTION TO ENTOMOLOGY 



important particulars. As with the horn-tails the body is cylindrical 

 but the last abominal segment is not terminated by a triangular or 

 lanceolate process. The back of the head is separated from the pro- 

 notum by an elongate neck; the pronotum is very short medially 

 and not angulate laterally; vein Sci is present in the front wings as 

 a transverse vein (Fig. 1 138) and the sheath of the ovipositor is seldom 

 longer than the last tergite. 



n^^^^M' 



Fig. 1 138. — Wings of Xiphydria maculata. (From MacGillivray.) 



The members of this family are of moderate size. Less than a dozen 

 species have been described from North America. 



The known larvae bore in dead and decaying wood of deciduous 

 trees. 



Family CEPHID^ 



The Stem Saw flies 



The stem sawflies are so-called because the larvae bore into the 

 stems of plants or in the tender shoots of trees and shrubs. The adults 

 are slender, elongate insects of moderate size. The pronotum is 

 more or less quadrate and longer than is usual in theHymenoptera. 

 The front wings are without a distinct cell between the costa and 

 vein Sc+R+M, and with cross-vein m-cu joined to vein M at or 

 near its separation from vein R (Fig. 1139). The anterior tibiae are 

 armed with one terminal spur. 



This family is of moderate size; less than a score of species have 

 been found in our fauna; but these represent nine genera. Some of 

 the species are of economic importance. Several species bore in the 

 stems of grains and grasses, the following species illustrate the habits 

 of these. 



