CHAPTER XXI 

 ORDER STREPSIPTERA * 



The Stylopids or Twisted-winged Insects 



The members of this order are small, endoparasitic insects, which prey 

 on other insects. Only the males are winged; in this sex, the fore wings are 

 reduced to club-shaped appendages; the hind wings are large compared with 

 the size of the tiny body, fan-shaped, furnished with radiating wing-veins, 

 and folded longitudinally when at rest. The adult female is larviform and 

 legless. The mouth-parts are vestigial or wanting; the alimentation is 

 probably by osmosis. Both sexes undergo a hypermetamorphos is . 



The order Strepsiptera comprises insects that were formerly classed 

 as a family of the Coleoptera, the Stylopidae; for this reason, these in- 

 sects have been known as the stylopids. Recently since the establish- 

 ment of the order Strepsiptera, the name the twisted-winged insects, 

 derived from the technical name of the order, has been proposed for them ; 

 but the old name is less cumbersome, and will probably continue to be 

 used. 



The stylopids are small insects which live par- 

 asitically within the bodies of other insects, chiefly 

 bees, wasps, digger wasps, and certain Homoptera. Their 

 small size and the fact that nearly their entire ex- 

 istence is passed within the bodies of their hosts re- 

 sult in their being rarely seen except by those who 

 are searching for them. During the first stadium the 

 young larvae of both sexes are free, and the adult 

 winged male leads a free existence for a brief period. 



The stylopids are most easily found by examining 

 adult individuals of the species of insects that they in- 

 fest, in which may be found adult females and male 

 men of 'styiopjzed pupa? of the parasites. The presence of a stylopid is 

 indicated by the projecting of the head end of the body 

 from between two of the abdominal segments of the host (Fig. 309). 

 Frequently a single host will contain several parasites. 



Figure 310 will serve to illustrate the appearance of an adult male 

 stylopid. The more striking features are the flabellate antennas; the 

 large, stalked, compound eyes; the shortness of the prothorax and the 

 mesothorax, and the great length of the metathorax; the reduction of 

 the fore wings to club-shaped appendages; and the large size of the 

 hind wings. 



The antennas of adult males differ greatly in form in the different 

 families of this order. The number of antennal segments varies from four 

 to seven. 



* Strepsiptera: strepsis (arpkipis), a turning; pteron (irTepov), a wing. 



176 



Fig. 3og. — Abdo- 



