592 



BRADLEY M. PATTEN 



similar curves plotted frora measurements made on larvae kept 

 isolated through the experiments. For the sake of simplicity 

 only six individual graphs have been plotted, but these have been 

 selected to show the range of variation in the group (fig. 4). 



3 Y y 6 7 8- 1 



Age of Larvae in Days. 



Fig. 3 Curve showing the average degree of photosensitivity from hatching 

 until pupation of a group of 50 C. erythrocephala larvae. 



DISCUSSION 



In working with the larvae from day to day certain differences 

 were observed in their reactions which were sufficiently char- 

 acteristic and constant to deserve mention. 



Larvae when just hatched were found extremely difficult to 

 handle without injury. Moreover, they were so small and their 

 muscular reactions were so weak that it was not always possible 

 to make them give a readily measurable trail. Quantitatively, 

 therefore, the first day measurements must be regarded as only 

 approximate. The trails shown in figure 2 A, are unusually 

 clear cut. In most cases it was necessary to watch the larva 



