228 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 2 



largely true for a given period, its reactions throughout the life his- 

 tory of the individual show progressive change, viz. : first, during the 

 feeding period the larvae as a body react positively to artificial light, 

 though as individuals they are apparently always strongly negative; 

 secondly, the migrated larvae (in the pre-pupal period) are uniformly 

 negative ; and finally, though the larvfe pupate as negative organisms, 

 they emerge in a positive state. (In this connection one should con- 

 sider the fact that the larvae are eyeless creatures, while the adults 

 possess well developed compound eyes.) The following table shows 

 this range of reaction of individuals to a given stimulus, light of 0.56 

 C. M. intensity. 



TABLE 1 



Summary of reactions of Lucilia caesar (Lot No. 10) at different ages to direc- 

 tive light C0.56 C. M.). Based on ten larvae given five trials each to an exposure 

 of thirty seconds. 



REACTION 



A further question which must be carefully considered is. Does the 

 behavior of the organism vary with the intensity of the stimulus and 

 what is the variation? This is again illustrated by another table 

 (Table 2), which shows the reactiveness to directive light for various 

 intensities of two species of flesh flies. Here is also illustrated the 

 difference in reactiveness of two related species to exactly the same 



1 This aberrant reaction was on the part of an individual whose wings did not 

 spread and was consequently forced to creep. All other adults first perched on 

 the edge of the vial in which they were retained and then flew toward the light. 



