SUBFAMILY XYLOCOCCINAE 85 



dently inconspicuous and were overlooked by Pergande. In the 

 female nymphs of the first stage the respiratory system consists of 

 a very short unconnected spiracular trachea near each spiracle. 

 Each of the tracheae is strongly constricted near the middle of its 

 length. These constrictions contain one or more rings of cerores. 

 With the growth and development of the nymph the spiracular 

 tracheae elongate and fork. The branches of the forks elongate, 

 the adjacent forks curve toward each other and finally fuse 

 forming a continuous system of longitudinal tracheae on each side 

 of the abdomen. Pergande in his description of the male nymph 

 of the third stage states: "pores and stigmatic tubes similar tc 

 those of the female in the second stage." 



This subfamily contains in addition to the genus Xylococeus, 

 three other genera: Coelostomidia containing four Australian 

 species described by Maskell with zealandica as type ; Ultra- 

 coelostoma containing a single Australian species; and Crypto- 

 kermes containing a single Brazilian species. 



The species of the above named genera agree so far as known 

 with those of Xylococcus in that they are either provided with a 

 chitinized rectal tube, excrete a long slender glassy tube of wax, 

 or their spiracular tracheae are provided with rings of cerores. 

 They differ, however, in the general shape of the body, which is 

 not always deeply imbedded in the tissue of the host-plant but in 

 some species is encased in a test of hard or comparatively hard wax 

 and attached to the surface of the bark or only slightly imbedded. 

 The legs and the antennae, although greatly reduced in size and 

 inconspicuous, are present in certain species and the thoracic 

 spiracles are large and prominent and the number of pairs of 

 abdominal spiracles is usually less than in Xylococcus. The genera 

 referred to this subfamily can be separated as follows : 



GENERA OF XYLOCOCCINAE 



a. Adult female with nine-segmented antennae and with well developed 

 legs; thoracic spiracles small and inconspicuous, at least in early 

 nymphal stages, smaller than abdominal spiracles; abdomen with 



eight pairs of spiracles. Xylococcus LOGW. 



aa. Adult female with more or less than nine segments in antennae, but 

 not with nine; legs wanting or well developed; thoracic spiracles 

 large and conspicuous, always larger than abdominal spiracles; ab- 

 domen with six or seven pairs of spiracles. 



b. Antennae of adult female always distinct, consisting of five or 

 more segments; abdomen, so far as known, with six pairs of 

 spiracles. 



