596 BKADLEY M. PATTEN 



large to justify any quantitative statements for L. sericata, it 

 was clear, nevertheless, that age differences greatly modified their 

 photic reactions. Herms ('11) has already shown that larvae of 

 Lucilia caesar become more strongly negative to light as they 

 grow older. He did not observe any drop in sensitivity during 

 the migratory period, but this might possibly have been due to 

 the fact that he did not use quantitative methods rather than to 

 the absence of the phenomenon in this species. These observa- 

 tions all indicate clearly the necessity of taking into considera- 

 tion the developmental stage of blowfly larvae used in photic re- 

 action experiments. 



Herms ('11) has also shown that there are differences in the 

 photosensitivity of the larvae of L. caesar and C. vomitoria. In 

 all probability more extended observations and more refined 

 methods, would show differences in the reactions of the larvae 

 of other common species of blowflies. It would seem super- 

 fluous to call attention to the necessity of recording the species 

 of the animal worked on, were it not for the fact that the liter- 

 ature on photic reactions abounds in references to the reactions 

 of 'blowfly larvae (sp. ?)'. 



A study of table 2 and figure 4 will make it apparent that for 

 accurate quantitative work it is not sufficient that all the in- 

 dividuals used should be of the same species and the same age. 

 It is necessary to employ in addition some preliminary standard- 

 izing test to exclude extreme individual variants. Only by such 

 means may data on photic reactions secured under different 

 experimental conditions be relied on for comparisons. Neglect 

 of species determination, failure to take into consideration the 

 developmental stage of the animals studied, and insufficient at- 

 tention to the factor of individual variability have undoubtedly 

 been responsible for much unnecessary controversy concerning 

 the reactions of 'blowfly larvae.' 



