84 THE COCCIDAE 



One of the striking features of the anatomy of the species of 

 Xylococcus is the chitinization of the caudal end of the rectum, 

 forming the so-called anal tube. This chitinized portion is pro- 

 vided with one to three rings of anacerores. This structure is 

 present in all the female nymphal stages. It becomes more and 

 more highly organized with each successive stage. Pergande does 

 not mention its presence in the adult female but states : ' ' The 

 anal opening is simple, situated on the underside of the abdomen 

 close to the concavity, and with difficulty to be seen." Florence 

 in her description of the adult female of each species, states : 

 "Anal tube represented by an infolding of the body-wall and not 

 strongly chitinized." It is apparent that the chitinization of the 

 rectum is peculiar to the nymphal stages as in Coelostomidea and 

 Icerya. The function of the rings of anacerores is to excrete the 

 long hair-like filament of glassy wax which is protruded through 

 the anus. These filaments are often two inches or more in length 

 and contain at the free end a viscid droplet of honey dew. The 

 male is provided with a chitinized rectum in the first three nymphal 

 stages and excretes a long glassy thread-like tube of wax like that 

 of the female. This tube is lost in the male at the third molt. 

 Where these insects are abundant, the large number of waxen 

 threads give the bark a hoary appearance. 



The body of the female and male nymphs is covered with 

 cerores which are more abundant along the lateral and caudal 

 portions. In this region there is excreted thick masses of wax 

 which undoubtedly aids in the curling and splitting of the bark. 

 The wax is in the form of curls which are consolidated into thick 

 lamellae on the sides of the body. 



The development of the respiratory system as described and 

 figured by Pergande is unique. He does not mention or figure 

 any thoracic spiracles but Hubbard states that "there are nc 

 spiracles anterior to the abdominal portion of the body in the 

 female." This is corrected by Florence. She makes the following 

 statement: "The insects have ten pairs of spiracles, two pairs 

 on the thorax and eight pairs on the abdomen. Those on the 

 abdomen have large simple openings, and within the body form 

 stigmatal tubes which are anterior constrictions in which there 

 are one or two rings of pores according to the instar. The thoracic 

 spiracles have no stigmatal tubes. In the active stages their 

 openings are marked by a small group of pores, and in the apodous 

 stages these pores are wanting." The thoracic spiracles are evi- 



