156 



a growth of dense whitish hairs, on both leaf surfaces and on the 

 stems. When the crop is more advanced, predacious CoccinelUd 

 larvae are noticeable in the colonies of mites. A very dry year seems 

 to have the effect of increasing the numbers of mites, while moisture 

 in the soil is thought to play an important part in reducing them. 

 Dusting and spraying the crop with lime and sulphur seem to have 

 little effect. A trial was made of steeping good quality seeds for 

 ten minutes in a solution of one part mercury perchloride in 100 parts 

 of water. The seeds were then dried in the shade and tests made for 

 germination, after which they were sown. The germination and 

 development of the plants were excellent. After about two months, 

 the mites began to appear, but the infestation was only about 0-4 to 

 0-5 per cent., compared with 3 per cent, or more in the untreated 

 plots. The removal of the first leaves that showed infestation was 

 also helpful in checking the progress of the pest. 



Ghosh (C. C). Supplementary Observations on Borers in Sugar-cane, 



Rice, etc. — Rept. Proc. 4th Ent. Meeting, Piisa, Fchriiarv 1921, 

 Calcutta, 1921, pp. 105-136, 10 plates. 



This paper is supplementary to a previous one [R. A.E., A, ix, 69]. 

 A great deal of fresh information concerning borers and other pests 

 is added ; a few more internal borers are dealt with, and fresh alter- 

 native food-plants for several others have been discovered. A new 

 key for differentiating the pupae is given, which supersedes that of 

 the previous paper. A key is given for distinguishing the borer larvae, 

 and the life-histories of 26 borers are dealt with. 



The damage by borers to rice in the Pusa neighbourhood does not 

 ordinarily exceed about 4 per cent. Further work on rice stem borers 

 is necessary in all the rice-growing Provinces. In the districts of 

 Bengal that have been examined, Schoenohins incertellus {bipunctifer) 

 and Chilo simplex were the chief ; in Burma the latter does not appa- 

 rently occur, and the former seems to be the most important borer. 



Recent experimental work with sugar-cane proves that the incidence 

 of attack by insects is correlated with climatic conditions. It is 

 especially during periods of drought that great damage is done by 

 insects, particularly in Pusa and many parts of Upper India, where 

 the crop is not irrigated, and where, owing to want of growth and 

 tillering of the plants, the loss due to pests is not compensated for. 

 At Pusa the chief injury to sugar-cane is caused in the early stages 

 of its growth in April, May and June, when the conditions generally 

 are high temperature and low humidity, with very little rainfall. 

 The relation between damage and climatic conditions holds good in 

 all varieties of cane, though thin ones show greater immunity than 

 thick ones and also greater resistance to drought. Particular varieties 

 are, therefore, suited to certain areas according to local climatic 

 conditions. As a rule, thick varieties are not suitable in Upper and 

 Western India. Certain varieties also show greater resistance to pest 

 attack, but no kind has yet been found to be wholly resistant. The 

 presence or absence of alternative food-plants in the locality exercises 

 a great influence on the occurrence of at least some of the borers in 

 sugar-cane. 



The problem of borer control is not so acute in Southern India, 

 where climatic conditions are favourable, as in the North, at Pusa for 

 example, where thick canes yield about 50 per cent, less than they 

 are capable of doing. Only one of every four shoots growing from 



