320 



JAMES W. McCOLLOCH AND H. YUASA 



instead of crawling down into the culm. It is interesting to 

 note that the larva seems to be unable to distinguish the right 

 direction from the wrong when deflected from the former; e.g., 

 larva 270-3, while moving down, was overtaken by larva 270-4, 

 which forced i 't into the adjacent groove. The larva 270-3 was 

 inverted completely by this treatment and when it started on 

 its way was moving toward the tip of the leaf. This one died 

 after moving 30 mm. 



Mortality of Larvae on Migration. — The larvae, during their 

 migration on the leaf, are in the critical period of their life and 

 it is probable that many of them die. That such is the case 

 is shown in Table VII, which gives the percentage of mortality 

 of larvae from both normal and inverted eggs. Table VIII 

 gives the details of the 68 larvae which hatched from the eggs 

 laid in inverted position and which died on the leaf during migra- 

 tion. It is interesting to note that 53% of these larvae failed 

 to reach the tip of the leaf. It is well to note, however, that 

 these larvae had traveled the average distance of 56.6 mm. 

 before they died. 



TABLE VII 

 Mortality of Migrating Larvae 



Larvae Larvae 



that got that 



Total down into died on Mortality, 



No. sheath leaf % 



Larvae from eggs laid normal 205 157 48 23.4 



Larvae from eggs laid inverted 119 51 68 57.1 



Total 324 208 116 32.7 



TABLE VIII 



Analysis of the Mortality of 68 Larvae that Hatched from Eggs 

 Laid in an Inverted Position 



