426 COLEOPTEllA OF NORTH AMERICA. 



of the abdomen; wings very large, fan-shaped, with a few 

 diverging nervures;- the epiinera are very hirge, and project 

 behind ahnost as lar as the postscutelluni. 



Abdomen small, with from seven to nine segments. 



Legs short; anterior and middle coxie cylindrical, promi- 

 nent; hind coxie very small, contiguous, quadrate; tibia; 

 without spurs; tarsi without claws, joints each with a mem- 

 branous lobe beneath. 



Females larviform, alwaj^s contained in the pupa case in 

 the body of the wasp or bee. 



This family contains a small numlier of species which, bv the 

 degradation of structure, have lost all resemblance to the other 

 members of the order Coleoptera. They were, from' the period 

 of their discover}' to within a few years, considered as a separate 

 order, under the name Strepsiptera, but a knowledge of the 

 transformations and a more rigid interpretation of the external 

 anatomy have convinced nearly all systematists of the propriety 

 of placing them as a family of Coleoptera. 



They are parasitic in the bodies of species belonging to various 

 genera of aculeate Hymenoptera; foreign genera have been dis- 

 covered which infest ants and Homoptera; the comparatively 

 large size of these parasites causes a distortion of the abdomen of 

 the Hymenopteron affected, and, on close observation, the heads 

 of the pupa cases may be seen emerging between the segments. 

 The head of the pupa case of the male is convex, that of the 

 female is flat; specimens containing male pupte can.be kept con- 

 fined witli proper food until the parasite is hatched. 



But two genera are yet known in North America, in both of 

 which the tarsi are 4-jointed. 



Anteniiffi with six joints. Stylops. 



Antennse with four joints. Xenos. 



Stylops inhabits bees of the genus Andrsena; we have never 

 met with specimens. Xenos Peckii lives in our common wasp 

 Polistes fuscata. ■ Stylopized individuals of Odijnerus quadri- 

 cornis, and of a large species of Sphex have been observed. 



It is very desirable that observers in the United States should 

 tiu-n their attention to the laborious but interesting task of col- 

 lecting the species of this family. 



