THE CHANGES OF THE BLOWFLY LARVA'S PHOTO- 

 SENSITIVITY WITH AGE 



BRADLEY M. PATTEN 



From, the Laboratory of Histology and Embryology, School of 

 Medicine, Western Reserve University 



FOUR FIGURES 



INTRODUCTION 



In previous work on the reactions of blowfly larvae (Patten, 

 B. M., '14), it was noticed that the sharpness with which orienta- 

 tion to a change of light direction was accomplished varied mark- 

 edly in different individuals. By observations incidental to the 

 experiments then in hand, I became convinced that at least a 

 certain amount of this variability in reaction was due to differ- 

 ences in the age of the maggots. 



A search through the literature showed that others had ob- 

 served changes in the blowfly larva's accuracy of orientation at 

 different ages. Pouchet ('72) states that their negative responses 

 become more marked as the animals advance in age, but that even 

 newly hatched maggots show a tendency to avoid strongly lighted 

 areas. Unfortunately the species on which he worked is not in 

 this case recorded. He speaks of them simply as the 'vers' or 

 'asticots' of the 'mouche a viande.' 



Herms has noted that changes take place with advancing age 

 in the photic reactions of larvae of Lucilia caesar Linne. One of 

 his tables ('11, p. 190) which gives the percentage of negative and 

 positive responses for a group of ten individuals at daily intervals 

 through their life history, indicates clearly that their negative 

 reaction becomes more pronounced as the larvae grow older. 



Working with larvae of Calliphora erythrocephala Meigen, 

 Gross observed that they too reacted differently at different ages. 

 He says ('13, p. 476), 



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THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 20, NO. 4 



