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A Contribution to Our Knowledge of the Stylopidae. 
By 
Charles Thomas Brues. 
(Contributions from the Zoological Laboratory of the University 
of Texas.) 
With plates 22, 23 and 3 figures in text. 
The following observations upon the anatomy and development of 
the Stylopidae are based upon the study of three North American 
species of Xenos. Two of these species, collected in Texas, seem to 
be new to science and are herein described. The third, Xenos pecku 
Kırgy, which was collected in great numbers at Colebrook Connecticut 
by Dr. Wm. M. WHEELER, has furnished the greater part of the material 
upon which the histological studies are based. Dr. WHEELER has very 
generously placed all this material at my disposal and has aided me 
throughout the course of my work by many kind suggestions and 
criticisms. 
The various species of Xenos, so far as has been observed, all 
live as internal parasites of different species of wasps and with few 
exceptions confine their attacks exclusively to social wasps belonging 
to the genus Polistes. Xenos peckii, the first form to be described 
from North America, was described by Kirpy in 1815, and has since 
received but little attention. It is parasitic upon two northern species 
of Polistes, viz: P. variatus and P. metricus. 
Although much has been written upon the life history and 
morphology of the Stylopidae, many of the details are as yet far from 
clear, and so far as I know, no one has as yet attempted a study of 
the embryogeny of any of these interesting animals. With the ex- 
ception of a ludicrous figure by Ficuier, our literature upon this 
subject seems to be an utter blank. 
