370 Dactylopiincc. 



its place for those species having antennas with eight or fewer joints, while the 

 species with nine-jointed antennae are referred to Phenacoccus. 



The dividing line between Pseiidococcus and Phenacoccus in the one 

 direction and Ripersia (with six to seven-jointed antenna^) in the other 

 direction, is not very satisfactory and can be accepted only as a more or less 

 convenient method of breaking up a cumbersome group. There are certain 

 species of Pseiidococcus in which a partial division of the terminal joint may 

 occur which — if complete — would relegate the species to Phenacoccus. On the 

 other hand, there are species of Phenacoccus in which the separation of the 

 eighth and ninth joints is but weakly defined. Again, there are species of 

 Pseiidococcus in which the number of antennal joints is reduced by more or less 

 complete fusion to seven or even six, thus bringing them within the definition 

 of the genus Ripersia. 



The genus is universally distributed, representatives being found in every 

 known country. Approximately 150 species have been described, of which 

 twelve are now recorded from Ceylon. 



For a first subdivision of the species, the position and arrangement of the 

 dermal spines will be found a convenient character. They are associated with 

 ceriferous pores, usually in well-defined groups in positions corresponding 

 with the waxy tassels that are commonly found on the living insects. These 

 groups of spines and pores have been termed ceriferous tracts or cerarii. They 

 are usually confined to the marginal area of the body and may form a complete 

 marginal series {e.g., citri, lo?tgispinus, &c.), or be confined to the posterior 

 segment only — as in virgatus — or they may be found on two or more of the 

 terminal segments of the abdomen. Ps. scrobicularum is an exception, 

 having the spines placed in transverse series across the abdominal segments ; 

 in this and in the character of the anal ring scrobicularum approaches the 

 species for which I have erected the new genus Erioides. The relative 

 lengths of the caudal setae and those of the anal ring and the size of the 

 spiracles are useful characters. The antennal formula, though useful in some 

 cases, is not altogether reliable, so much depends upon the condition of the 

 specimen and of the preparation ; and, in many species, the relative dimen- 

 sions of the antennal joints themselves are variable. The length of the tarsus 

 in relation to the tibia is a more reliable character. 



A character that appears to be common (though not confined) to the species 

 of Pseiidococcus is the presence of two pairs of large oval glandular cicatrices 

 (foveas, or osteoles) which are situated on the dorsum — one pair near the anterior 

 extremity and the other near the posterior extremity of the body. They are 

 concerned in the secretion of a fluid — probably of an offensive nature — which is 

 exuded when the insect is irritated. 



Synopsis of Ceylon Species. 



A. Ceriferous tracts on terminal segment only. 



(a) Limbs long and slender virgatus. 



(J)) Limbs short and stout kandyensis. 



B. Ceriferous tracts on terminal and penultimate segments 



only. Body elongate. 



[a) Limbs and other organs proportionately small pulverarius. 



(b) Limbs, &r., proportionately large pulverariiis-bambuscE. 



C. Spines in conspicuous transverse bands across abdomen ... scrobiculatum. 



