86 SCIENTIFIC REPORTS OP THE AGRICULTURAL RESEARCH 



Rice. Stem-borers in rice were under observation 

 throughout the year as far as it was possible with the staff 

 available. The insects concerned were (1) Schoenobius 

 bipunctifer, (2) Chilo simplex, (3) a second species of Chilo, 

 as yet unidentified and apparently undescribed, hitherto 

 confused with C. simplex ; this is for the present called Rice 

 Chilo, (4) Sesamia inf evens. 



Whilst rice was growing it was observed that the 

 prevalence of these borers varied from field to field and also 

 to some extent according to the age of the plants. Con- 

 siderable further observation is required in order to arrive 

 at definite facts and conclusions regarding their relative 

 prevalence. 



Sesamia inf evens remained active throughout the year, 

 whilst the other three species mentioned above hibernated 

 in the stubble. In order to observe the hibernating habits 

 of these insects four large rice fields outside the Pusa Estate, 

 amounting in the aggregate to about 180 acres, were kept 

 under observation throughout the cold weather from Decem- 

 ber to March, samples of stubble being collected at intervals 

 from all over these fields and examined. As a result of the 

 examination of 18,514 stubble-stems it was found that : — 



(1) Reckoning as affected only those stems which showed 

 distinct signs of borer attack, the percentage of damage 

 varied from 14 to 55 in the various countings and on the 

 average was about 29. As attack by a borer causes the 

 entire ear to fail to develop, this percentage may be taken 

 as representing the proportion of chaff in the harvested 

 grain. 



(2) At the lowest computation there were about 30,000 

 larvae hibernating in each acre of the rice fields in December. 

 This number fell to about 15,000 per acre towards the end 

 of March. This reduction was apparently due to the fact 

 that, as the temperature rose at the end of the cold weather, 

 these hibernating larvae became active and left the stubble, 

 and either fell victims to natural enemies or took shelter in 

 cracks in the soil. In the samples of stubble, however, 

 there was no sign of the presence of any enemy worthy of 



