36 THE COCCIDAE 



group of the hoad and the caudal group of the abdomen are 

 generally subadjacent. 



Anus. — The external opening of the caudal end of the alimen- 

 tary canal, the anus, is normally located in the tenth segment. 

 In the Diaspidinae the caudal portion of the abdomen is strongly 

 depressed and the anus is usually a circular opening located on the 

 dorsal aspect. It varies considerable in position, in some species 

 it is located near the cephalic portion of the strongly chitinized 

 pygidium, in others near the caudal end, and in still others it is 

 intermediate in position between these two. In the Lecaniinae 

 and Asterolecaniinae the anus is located at the cephalic end of the 

 invaginated barrel-shaped anal tube. It is usually surrounded by 

 an anal ring at this point and is not located on the exterior of the 

 body as might be expected. 



Vulva. — The external opening of the female reproductive 

 organs is the vulva. It is located on the ventral aspect generally 

 near the caudal margin of the sixth segment. There are frequently 

 accessory structures associated with it which make its location more 

 easily identified. Figures of the caudal portion of the dorsal or 

 ventral aspects of the abdomen of coccids generally show the 

 position of both anus and vulva on the same drawing, this does not 

 mean that they are both situated on the same aspect. In the 

 Diaspidinae the vulva is usually located near the middle of tlie 

 pygidium. 



Spiracles. — The external openings of the respiratory system, 

 the spiracles, also known as stigmata, are usually distinct and are 

 always four in number. The cephalic pair, the mesopiracles. 

 belong to the mesothorax and the caudal pair, the metaspiracles, 

 to the metathorax. These spiracles are normally located in the 

 mesocoria and metacoria. In the leg bearing species, the 

 mesospiracles are located about midway between the articulations 

 of the prothoracic and mesothoracic legs and the metaspiracles 

 about midway between those of the mesothoracic and metathoracic 

 legs. In the Diaspidinae the adults of which are always legless, 

 the mesothoracic spiracles are located one on each side of the 

 rostrum, sometimes designated as the head spiracles, near where the 

 prothoracic legs are ordinarily-' larticulated. The metaspiracles 

 are apparently not different in location from that of the species 

 with legs. The spiracles are the only landmarks available in 

 many legless coccids for indicating the thoracic segmentation. 

 They are greatly reduced in size in the genus Xylococcus and were 



