insect the cephalathorax. In Xcnos the opening of the brood- 

 chamber appears to be anterior to that in Elcnchiis. This appear- 

 ance is evidently due to the flattening of the cephalothorax and 

 forward growth of the prothorax. 



The female larva in the second stage can be distinguished, 

 whilst still very small, by the presence of what Bntes terms the 

 primitive eggs, at first indefinite areas along the back, but eventu- 

 ally becoming scattered about among the fatbodies. The head 

 of the adult female never leaves the apical cap of the puparium, 

 but the abdomen, distended to an enormous extent by the number 

 of eggs, bursts through the dorsal side of the puparium. The 

 skin of the puparium remains attached to the ventral side of the 

 insect and forms the brood-chamber (Fig. 7). Three ducts open 

 into the brood-chamber, through which I have found triungulins 

 issuing (Fig. 8). Through one or more of these ducts fecunda- 

 tion must take place, but as the eggs all develop simultaneously 

 the spermatozoa must become dispersed among the fatbodies. 



The cephalic cap of the female and male puparium are homolog- 

 ous. In the female the labiumi and other mouth parts are turned 

 under at an acute angle, leaving a hole which forms the entrance 

 to the brood-chamber. At each side of this hole the prothoracic 

 stigmata are visible. 



I have not been able to dissect the adult female Elcnchiis free 

 from the cephalic cap, but in a species of Xcnus, attacking a 

 species of Polistes in Honolulu, I have dissected the adult female 

 free from the puparium. It can then be seen that the mouth parts 

 are more like those of the male larva than of the adult male ; and 

 we might say that the female development is arrested at the larval 

 or perhaps pupal stage. The female head when dissected out 

 from the apical cap is interesting, as it tends to confirm Dr. 

 R. C. L. Perkins' interpretation of the position of the mouth open- 

 ing of the male. 



The fact that histolysis reduces the muscular system of 

 Elenchus larvae more thoroughly than in any other genus of 

 Stylopidae, that the female is less dififerentiated, that the male 

 antennae are reduced to two branches, its tarsi to two joints, indi- 

 cates that this genus is the most specialized of the Stylopidae. 



Opinions differ as to the effect of stylopization on the host. 

 Dr. R. C. L. Perkins gave me a dissection of a Polistes bearing 

 two full grown female Xenos and several larvae, in which the 

 internal organs of the Polistes were in perfect condition. In the 

 case of the Vitian leaf hopper stylopization had a very harmful 

 effect. The host only lived a short time after a male Elenchus 

 hatched out or the young left the brood-chamber of the female. A 

 stylopized female hopper seldom could produce eggs on account 



