142 Mr. K. Kunhi Kannan on 



of Lecanium (Coccus) in Mysore this habit has not been 

 found or is slight and inconspicuous. In Coccus viridis it 

 is so great that the dorsum may be thrown into minute 

 folds (PI. VIII, fig. 3). It is difficult to explain this except 

 as an inherited tendency persisting after the necessity has 

 disappeared. 



If the difference between psidii and viridis appears, 

 then, of little importance, the difference between psidii 

 and the Javan round form is much less. The structural 

 characters of these two are, as I have already shown, 

 identical. The only serious difference is in the method 

 of reproduction. The Javan round form is thus inter- 

 mediate between psidii and viridis. The series of forms 

 commencing from psidii on one side and extending to 

 viridis and colemani on the other, exhibit a gradual de- 

 generation not by fluctuating variation but by saltatory 

 variations, or what De Vries would call retrogressive 

 mutations. For, on the one side, we have a meal-secreting 

 habit, more numerous and larger cells in the derm, strong 

 marginal setae, a larger size, and eight-segmented antennae, 

 and at the other end a smaller size and three-segmented 

 antennae, absence of meal, less numerous and more rounded 

 cells in the derm and very feebly developed marginal setae. 

 The intermediate types approach one or other of these 

 extremes, and some of them are extremely unstable. The 

 conclusion appears therefore to be justified, that Coccus 

 viridis arose as a mutant from Pulvinaria psidii, and the 

 various forms from South India, Java and Uganda are 

 derivatives from the latter species either directly or through 

 C. viridis. 



This hypothesis that two species which are placed in 

 different genera have mutational relations is the only one 

 that fits the facts given above. Short of actual demon- 

 stration, it is difficult of acceptance at first sight, and 

 demonstration is difficult under the widely different con- 

 ditions of distant countries in which the mutations have 

 occurred. It does not appear probable that the various 

 forms so produced can all be produced in one of these, 

 especially when the parthenogenetic condition of these 

 forms prevents their crossing. South India yields only 



of disease, and commonly occurs in the incipi< n! slaps of infection 

 by the parasitic fungus Cephatosporium. 1 have never observed a 

 healthy insect in tins position. — E. E. Ci. 



