NOTES ON THE LIFE HISTORY OF THE STYLOPID/E. 



CHARLES THOMAS 1 1 RUES. 



During the past summer I had the opportunity of making a 

 number of incidental observations on the two Texan species of 

 Xenos, and of discovering the female of one of them, which has 

 not hitherto been described. As these notes throw some light 

 on the life history of these interesting creatures, I venture to pre- 

 sent them at this time. 



On May 22, at Paris, Tex., I captured a large overwintered 

 female of Polistes riibiginosus which had evidently just left its 

 hibernation quarters. Examination showed that it harbored a sin- 

 gle female specimen of Xcnos nigrescens Brues. The head of the 



parasite protruded between two 

 of the apical abdominal segments 

 and a number of triungulins were 



o 



emerging from the small rect- 

 angular orifice on the anterior 

 portion of the exposed surface 

 of the head. The triungulins do 

 not move very rapidly and cling 

 rather tenaciously to the body 

 of the wasp, even when the lat- 

 ter is shaken violently about. 

 They keep continually in motion, 

 however, and when the wasp is 

 resting a number of them are 

 always crawling off upon adja- 

 cent objects. They are rather 



dafk brown m co j or &nd scarcd 



visible to the naked eye. The 

 following description is drawn up from a number of mounted 

 specimens : 



Length .28 mm. Oval, head obtusely rounded anteriorly. Head and 

 thorax together slightly longer than the abdomen. Head a little less than 

 half as long as the thorax, almost semicircular when seen from above, being 



290 



FIG. I. Triungulins of Xenosnigrescens 

 Brues. a, dorsal view ; />, ventral view. 



