THE MIGRATION OF THE FLY LARVAE 309 



the ground, or may die, and in dried and shriveled condition 

 remain for a time on the leaf." After performing some experi- 

 ments to see if the larva could follow the creases of the blades 

 up an incline, if it were necessary for the ]arvae to do this, in 

 order to reach the base of the culm, they state (p. 5.) that "in 

 no instance did a larva make more than a slight advance up- 

 ward, and most of them, died with their bodies extended cross- 

 wise of the creases, near the points where they had hatched." 

 They add that the bearing of this experiment on the following 

 statement quoted by Packard (1883, p. 212) is readily appre- 

 hended: " A reason given by some why the fly does not injure 

 red wheat as much as white, is because the leaf of the red grows 

 so long and slants down from the shoot, so when the egg hatches, 

 the maggot works down the wrong way, falls to the ground, and 

 so many fail to harm the wheat." 



Headlee and Parker (1913, pp. 95-96) state that the larva 

 ' seems to have various means of getting ' down into the plant ; 

 some observations made by Mr. Kelly would indicate that in 

 the presence of abundant dew it is washed down by the droplets 

 of water. In other cases it undoubtedly crawls down, earth- 

 worm-like, following the groove until it reaches the place where 

 the leaf -sheath winds tightly about the stem. Get down as it 

 may, when once there it squeezes in between the leaf -sheath 

 and the main stem and continues its way downward until it 

 nearly reaches the point where the leaf takes its origin. Just 

 above this point it stops and begins to feed." 



METHODS OF STUDY 



The experiments on which this paper is based were carried 

 on in the breeding chambers of the air conditioning machine 

 described by Dean and Nabours (1915). The temperature was 

 maintained at approximately 70° and the humidity at about 

 70%. The wheat plants were grown in wide-mouth bottles 

 containing Pfeffer's liquid plant food solution. 2 The roots of 



2 Pfeffer's solution for wheat cultures is prepared as follows: 



Calcium nitrate 4 grams 



Potassium nitrate 1 gram 



Magnesium sulphate 1 gram 



Potassium dihydrogen phosphate 1 gram 



Potassium chloride 0.5 gram 



Ferric chloride Trace 



Distilled water 5 liters 



