NOTES ON THE LIFE HISTORY OF STYLOPID.E. 29 1 



truncate behind. Eyes large, strongly pigmented. Oral opening large, 

 almost contiguous with the eyes below ; mouth parts consisting apparently 

 of a short proboscis-like organ with chitinous sides. No antennae or other 

 tactile organs to be seen. Thorax one and one-half times as long as wide, 

 consisting of three nearly equal transverse segments. Each segment below 

 bears a pair of very small and delicate legs. The coxae are all greatly 

 swollen and globose, those of each side contiguous with one another and 

 the pairs only moderately separated along the median line. Each coxa is 

 hollowed out below and the trochanter sunk within it. Femora slender, 

 enlarged somewhat at the base, bearing a spine apically. Tibiae slender, 

 of equal width, the hind ones with a preapical spine. Tarsi greatly re- 

 duced, those of the four anterior legs scarcely distinguishable from the tips 

 of the tibia;, furnished with a pulvilliform appendage ; the posterior pair 

 elongated, with a styliform appendage. Abdomen consisting of nine short, 

 transverse segments and an elongated tenth segment which encloses the 

 extrusible tip of the abdomen (i ith segment ?). The dorsal sclerites reach 

 far clown on the sides, as do also those of the thorax, making the under- 

 side of the body somewhat concave. Tip bearing two approximated 

 bristles, each as long as the abdomen, in addition to a much shorter one at 

 each lateral angle of the last segment. 



The triungulins are strongly campodeiform in type, but show 

 several remarkable adaptations in the shape of the legs. Aside 

 from these peculiarities they are very similar to Meloid triun- 

 gulins. 



There are several differences to be noted between them and the 

 triungulins of Stylops as figured by Packard ('98, 695) and Sharp 

 ('01, 300). Principal of these is the presence of a pair of large, 

 strongly pigmented eyes, and the structure of the legs in which 

 the tarsi are so much reduced. In Packard's figure the different 

 form of the anterior and posterior tarsi are shown somewhat as I 

 have observed them in Xenos. 



Of the three species of Polistes which are especially abundant 

 in Texas, only two seem to be at all generally attacked by Xenos. 

 These are Polistes annnlaris and P. rubiginosns. From the for- 

 mer both Xenos pallidus and X. nigrescens were bred in consider- 

 able numbers, and from the latter only X. nigrescens, and that in 

 smaller numbers. The fewer Xenos obtained from the specimens 

 of rubiginosns is due both to the smaller percentage of individ- 

 uals infested and usually to the occurrence of only one parasite 

 in each wasp. In annnlaris there were on an average from three 

 to four Xenos in each parasitized wasp, and in one case ten fully 



