INSTITUTE, PUSA, FOR 1917-18 73 



more sluggish at 73° than at 88° F. provided they have not 

 fed recently, but active, well-nourished worms taken 

 directly after feeding show little difference in motility at 

 the two temperatures. At low temperatures there is 

 ordinarily little tendency to ascend shoots projecting out 

 of the water even when the air is approximating to satura- 

 tion, but here again freshly fed worms seem somewhat more 

 active than those that have been dried for some time. 



Light is also a factory -but the results so far obtained 

 require further testing. 



Starvation is a factor of great importance, In one 

 experiment two batches of 20 worms were placed in drops 

 of water on slides in a saturated atmosphere, one batch con- 

 taining only worms that had not fed for 18 days, the other 

 worms taken after they had had access to living young 

 paddy shoots.. In 24 hours all but 4 of the former batch 

 had left the water and were wandering freely in the cham- 

 ber, whereas in the other batch none had left the drop. 

 Four days later only 1 was left in the first drop while 19 

 were still in the second. 



Hence amongst the factors which control the wander- 

 ings of the worm in search of the food that it can only 

 obtain from the living paddy plant, some, such as humidity, 

 are absolute in that they impose conditions which rigidly 

 limit the power to move, while others are relative in that 

 they act through the instinctive or other vital processes of 

 the worm and so influence its movements indirectly, and are 

 more variable in their action. 



In carrying out such enquiries progress is necessarily 

 slow, since the period during which the work can be done 

 is limited each year, and all the work has to be done under 

 microscopic control, the worm being invisible to the naked 

 eye. 



As an indication of their practical application, it is 

 sufficient to mention that in certain districts the earliest 

 attacks take place on the aus paddy growing in close proxi- 

 mity to or even mixed with the main crop, and that as the 



