MISCELLANEOUS NOTES. 



663 



some other modus operandi of a more direct kind such as poisoning or 

 digging up of burrows in the breeding season. But it is beyond the scope 

 of this note to do more than draw attention to the impending evil. 



L. J. SEDGWICK. 



Dharwar, Ith January 1919. 



It may be argued that if the multiplication of rats is due to decrease 

 in prevalence of ticks then the greatest prevalence of rats should occur in 

 the year following the greatest decline in ticks, i.e., (in this case) 1919-20. 

 But if we assume that the recovery of the ticks is spread over two or 

 more seasons it may take time for the repressive influence of the ticks to 

 get the better of the impetus which has been given to rat-multiplication in 

 the meanwhile. The appended theoretical graph will explain this argument. 

 It will be noticed that the rat prevalence begins to fall at the point where 

 the tick prevalance riches the half way point between maximum deficiency 

 and normal. The graph is drawn on the assumption that the monsoons of 

 1917, 1919, 1920, 1921, 1922 and 1923 are normal. In practice the actual 

 graphs would be much more complicated, and in a long series of years 

 the two lines would constantly cross. 



Maximum possible excess. 



50 % excess. 



Norma). 



50 % deficit. 

 Maximum possible deficit. 



■ 



= prevalence of ticks. 

 — prevalence of rats. 



Mr. Sedgwick has done well to call attention to this interesting phono- 

 mena which is of such great economic importance. 



The first thing we want to know is what are the kinds of rats, which 

 cause these plagues, and I would appeal to members to send in specimens 

 of rats should there be a plague next year. Of the more recent plagues 

 there is not, as far as we know any record of the species concerned, but 

 fortunately two good naturalists Sir Walter Elliot and the Rev. Mr. Fairbank 

 of the American Mahratti Mission at Ahmednagar have put some facts on 

 record. Sir Walter Elliot writing in the Madras Journal of Lit. and 

 Science many years ago remarked that owing to "The monsoon of 1826 

 having been deficient at the commencement of the season, the mettades 

 bred in such numbers as to become a perfect plague. They ate up the seed 

 as soon as sown and continued their ravages when the grain approached 

 maturity, climbing the stalks of the jowaree and cutting ofl' the ears to 



