EXTERNxVL ANATOMY 39 



appears cleft or emarginate. Each anal lobe bears one or more 

 large setae, the anal setae. These setae probably serve as a core 

 to support the wax filaments excreted by the cerores of the anal 

 lobes. 



The presence of an anal ring with anal ring setae and of 

 anal lobes with anal setae seems to be closely correlated. The 

 modification of these structures shows them to be much older in 

 their development than the pygidium of the Diaspidinae which is 

 typically perfect only in the adult female. The anal ring and 

 anal lobes, if present in any stage, are more likely to be found in 

 the first nymphal stage and, if atrophy or modification of parts 

 has begun to take place, it starts with the adult and finally extends 

 into the older nymphal stages. Such changes may be confined to 

 the adult alone. The typical number of anal ring setae is six in 

 the first nymphal stage, although there may be more or less in the 

 other nymphal stages and the adult. A large number of the 

 species lacking an anal ring and anal ring setae in the adult have 

 six anal ring setae in the first nymphal stage. The modification 

 of these structures may extend into the first nymphal stage which 

 is shown in the reduction in the size of the anal ring setae and 

 later in the number of these setae to four, two, or none, and going 

 hand in hand with this change is a segmentation of the anal ring 

 and finally the complete loss of the anal ring itself. There is 

 generally a change in the form and a reduction in the size of the 

 anal lobes associated with the modification of the anal ring, but 

 the anal lobes like the anal ring reach their most perfect develop- 

 ment in the first nymphal stage. Some of the subfamilies, as the 

 Diaspidinae, which have evidently been derived from the line with 

 anal lobes, an anal ring, and anal ring setae, in the first nymphal 

 stage of many species have the anal lobes either obscure or so they 

 can be traced, but are always provided with two large prominent 

 anal setae. The position and form of these setae show unques- 

 tionably their homology. They are peculiar to the first nymphal 

 stage. 



