THE CANADIAN ENTOMOLOGIST. 257 



THE LIFE HISTORY OF XENOS. 



BY HENRY G. HUBBARD. 



How often, in turning over the pages of his check-list, has the Ameri- 

 can collector of beetles allowed his eyes to rest a moment upon those 

 lines of type which announce the existence in our fauna of the mysterious 

 family Stylopid;>3, with its two genera, Stylops and Xenos., each represented 

 by a single species ; but, recognizing in these names only the records of 

 captures almost legendary in their antiquity, he has turned the page with 

 a feeling that they represent to him unattainable rarities. In fact, to most 

 minds they bring to remembrance only the remarkable bat-like figure of 

 the male Stylops, which for generations has done duty in all the encyclo- 

 pedias and text books. But why should these insects be considered 

 unattainable rarities ? Are they as rare in nature as their vacant places 

 in our collections would seem to indicate ? I do not hesitate to assert 

 that they are not. If we question any hymenopterist of experience, he 

 will tell us that Stylopized bees and wasps are not uncommon. By this is 

 meant that specimens of hymenoptera are found having certain chitinous 

 particles protruding from their hinder bodies, appearing at the sutures 

 between the abdominal segments. These betray the presence in the wasp 

 or bee of either the female or the pupa of the male parasite. In the first 

 case the so-called head of the female presents only a bluntly-pointed 

 scale, so flat and thin that it hardly raises appreciably the horny covering 

 of its host, and, at most, barely peeps out beyond the edge of the over- 

 lapping plate. The pupa of the male, on the other hand, is a cylindrical 

 capsule of considerable thickness, and often distorts the smoothly tapering 

 abdomen of the hymenopteron. Its darkly chitinous, convex end pro- 

 jects boldly forth, and certain little tubercles upon its surface form a 

 grotesque face, with staring goggle eyes, which are in fact faceted, and 

 perhaps give a limited amount of vision to the nymph imprisoned within. 

 When the winged male of the parasite issues from this capsule, the mask- 

 like face is pushed off like a cap and falls to the ground. As a rule, when 

 stylopized hymenoptera are captured in the field, the male parasites have 

 long since issued, and hence their rarity in our collections. But the 

 females never leave the bodies of their hosts, and might be readily 

 obtained at certain seasons. 



In general it has long been known that Stylops inhabits bees, and 

 Xenos wasps of the genus Polistes. As far as I know the male of Stylops 

 is not to be found in any American collection, bu.t specimens of Xe^Q^ 



