U6 



Mr. K. Kunhi Kannan on 



Mysore there is at least one instance where such relation 

 appears to occur. This is under investigation. It is sig- 

 nificant in this connection that there are several species 

 in Pulvinaria in which there are well-marked varieties. 

 Newstead merges in Pulvinaria vitis the following species, 

 P. betulae, P. solids, P. oxyacanthae, and P. persicae, but 

 retains P. ribesiae as a variety. Similarly the limits of 

 variation are great in P . floccifera, in which also a number 

 of species have been merged. The study of species like 

 these will throw considerable light on the relationships of 

 the various genera and species of Coccidae. 



Even more important and valuable will be the instances 

 of mutation which the study is likely to bring to light. I 

 give below two instances which furnish a very close parallel 

 to the phenomena which I have described, where therefore 

 mutation must have occurred. In a most interesting paper 

 on " Some comparisons of Coccus citricola and C. hes- 

 pendum" Mr. H. J. Quayle, of the University of California, 

 gives an account of the relationships between the two 

 species, which are almost similar to those between P. psidii 

 and C. viridis. I summarise below the differences between 

 the two species. 



C. citricola. 



Antennae with 8 segments in 

 the great majority. 



Ground-colour grey or dirty 

 white. A more even distribu- 

 tion of dark colour pigment. 



Lustre dull. 



Shape oval, not variable. 



Male found occasionally. 



C. hesperidum. 

 Antennae with 7 segments. 



Ground-colour distinctly yellow- 

 ish. Colour pigment coalesced 

 in more or less definite areas. 



Lustre shiny. 



Shape variable: one side straight, 

 the other curved. 



Male unknown. 



C. citricola is the more variable of the species. Quayle 

 says : " In 78 specimens of citricola in which 139 antennae 

 were examined there were three scales each with seven 

 joints in one antenna and eight in the other. In four 

 scales there were seven joints in both antennae, and in 

 four others there were seven joints in one antenna, while 

 the other was not examined. The remaining number, or 

 67, had eight joints in both antennae. In 73 specimens of 

 hcsjieridnni examined all had seven joints." The paral- 



