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VII. An Instance of Mutation : Coccus viridis, Green, a 

 Mutant from Pulvinaria psidii, Maskell. Bv K. 

 Kunht Kannan, M.A., F.E.S. 



[Read March 6th, 1918.] 



Plates V— VIII. 



Summary. 



Coccus viridis, Green, has seven segments in the an- 

 tennae. This was so in the Mysore specimens when the 

 pest first appeared in the State in 1912. But specimens 

 collected in 1913 and afterwards, though undoubtedly 

 0. viridis in other respects, showed in the antennae a 

 reduction to three segments by the coalescence of the 

 terminal five into one. This indicated an instability in 

 the species, which has now been placed beyond a doubt 

 by the fact that there are in Java, besides the typical 

 C. viridis, two distinct types, with very variable but 

 usually eight antennal segments, highly unstable and with 

 a host of intermediate forms. A new form from Uganda, 

 described first as a subspecies, has been recently given 

 specific rank by Newstead. C. viridis is therefore clearly 

 unstable. 



Pulvinaria psidii is also very variable in size, antennae, 

 and anal plates, and some variations distinctly recall those 

 of C. viridis. The chief distinguishing feature, of the 

 secretion of meal for oviposition, may also be absent. 

 P. ■psidii has, moreover, at least two subspecies. The gap 

 between P. psidii and C. viridis being bridged over by the 

 variations in both these, involving the same structures, 

 and being in the same direction, P. psidii is the mutating 

 species, C. viridis and its variants being derived directly 

 or indirectly. 



Similar relations between species in Coccidae have been 

 noticed by others, and are best explained by the theory 

 of Mutation applied as above. An exact parallel to the 

 phenomenon, which occurred in C. viridis, has been noticed 

 by Green in Phenacoccus mangiferae. The relations de- 

 scribed by Quayle, of the University of California, between 

 Coccus citricola and C. hesperidum are also similar to 



TRANS. ENT. SOC. LOND. 1918. — PARTS I, II. (DEC.) 



