126 Transactions. — Zoology. 



Lecanio-diaspidas of Targioni, Planchonia loses its antennae, Lecaniodiaspis 

 keeps them. But it appears to me that there is an organic difference 

 between the secretion of a test, whether of wax, or felt, or cotton, and the 

 absence of any test at all. The difference between the naked genus Lecanium 

 and the covered genus Ceroplastes is, I take it, much greater than that 

 between Ceroplastes and Vinsonia. 



In my paper of 1878 (Trans., vol. xi., p. 207), I introduced the subsec- 

 tion Lecanio-diaspidas with an extension of its limits ; and I was led to this 

 in great measure because the term itself seemed so apt for expressing the 

 main difference between certain genera and the rest of the Coccid family, 

 that is, the possession of certain characters common to all Lecanidas 

 together with the formation of tests as in the Diaspidas (though not neces- 

 sarily including any pellicles). I then added to the subsection the genera 

 Ctenochiton and Inglisia, and in my paper of 1881 (Trans., vol. xiv., p. 221) 

 the genus Lecanochiton. 



There appears to be only one character common to all the Lecanidaa 

 which can be easily and clearly made out. It is the presence, at the 

 abdominal extremity of the female, of a more or less deep cleft, above which, 

 on the dorsal side, are two small protruding (usually more or less triangular) 

 lobes. Other characters, of course, exist, such as the generally monomerous 

 mentum, the usually stationary position of the adult female, the antennas 

 with almost always (in the adult) six or seven joints, and so on. But these 

 distinctions cannot always be exactly observed. For instance, it is often 

 exceedingly difficult, if not impossible, to tell whether the mentum is 

 monomerous or dimerous. But, as far as my own observation goes, and 

 from the description of M. Signoret and others, I know of no species of 

 Lecanidas which does not exhibit quite clearly enough the abdominal cleft 

 and its two lobes. In the group Diaspidas the abdomen has no such' 

 appearance : there is sometimes, as in Chionaspis dubia, mihi, or Diaspis 

 tosoj, Sandberg, a slight median depression, but the whole form of the part 

 is quite distinct. In the group Coccidas the abdomen either has no appear- 

 ance of division, as in the Dactylopii (see fig. 19 g., Trans., vol. xi., pi. 

 viii.), or else ends with prominent processes, which I have called "anal 

 tubercles," as in Eriococcus hoherice, mihi (Trans., vol. xii., pi. vii., figs. 

 14, 20). I append to this paper (figs. 22, 23, 24, and 25), diagrams to give 

 a comparative view of the three groups. 



It follows then that the group to which an insect belongs can be at once 

 discerned by reference to the abdominal extremity. There is one exception 

 to this in the insect producing stick-lac, Carteria lacca, where the cleft and 

 lobes are not easily made out ; and there are the genera Kermes, Pollinia, 

 etc., where the adult insect shows the cleft and lobes of Lecanidae while the 

 young has the anal tubercles of Coccidas. But exceptions prove the rule. 



