318 



JAMES W. McCOLLOCH AND H. YTJASA 



the propulsion of the body of the larva. The process of orien- 

 tation following hatching usually places the larva in a groove 

 within the radius of the length of the body, which may be the 

 first or second groove from the one in which the egg was laid. 

 Once in a groove, the larva follows it down or up, as the case 

 may be, until it reaches the end of the chosen path. In the 

 case of normal deposition, this is the base of the blade where 

 the short erect ligule which surrounds the stem arises. The 

 ligule is a barrier which every larva must overcome, either by 

 crawling over, as the majority of the larvae seem to do, or by 



Fig. 3. — Chart showing- the distance traveled and the rate of migration of five 

 larvae hatching from eggs laid in an inverted position. The dots indicate 

 the location of the larvae at the time of observation. 



avoiding it entirely by finding elsewhere a point of entry be- 

 neath the leaf-sheath. The larva, under favorable conditions, 

 such as a clean, smooth ligule which is loosely wound around 

 the stem, gets between the sheath and the stalk in a compara- 

 tive short time. When the conditions are adverse, such as 

 dirty, hairy, tight-fitting ligule and dry weather, the larva 

 finds it extremely difficult to surmount the barrier and, in many 

 cases, death overtakes it at this point, the usual mortality at 

 this situation under experimental conditions being about 25%. 

 The locomotion of the larva after it gets below the ligule has 

 not been studied. When the larva, directed by the initial pro- 

 cess of orientation, moves upward and reaches the tip of the 



