THE PHOTIC REACTIONS OF SARCOPHAGID FLIES 



193 



tion of the larva was noted and recorded. Records in total dark- 

 ness were taken in the same manner with the aperture for light 

 entirely closed. 



Table 5 is a summary of all records for both species. 



TABLE 5 



Reactiveness to directive light through the general range of intensity for migrated 

 larvae of Lucilia caesar {Lots no. 6 [A] and no. 25 [B\), and of Calliphura 

 vomitoria {Lot no. 24-)* 



REACTIONS 



SOURCE OF LIGHT 



INTENSITY IN C. M. 



L. caesar 



C. vomitoria 



Diffuse daylight. 

 Arc light 



800. 



Incand. light. 

 Incand. light. 

 Incand. light. 

 Incand. light. 

 Incand. light. 

 Incand. light. 

 Incand. light . 



0.56 



0.1764 



0.0342 



0.00705 



0.00176 



0.00063 



0.00007 



(A)0 

 i(A)0 



!(A)1 

 '(A) 5 

 1(A) 6 

 XB)0 

 (B)2 

 '(B) 5 

 |(A) 1 



Total darkness |(A) 2 



50 

 50 

 44 

 37 

 35 

 33 

 28 

 14 

 3 

 2 



18 

 20 

 28 

 46 

 46 





 3 

 3 



10 

 13 

 19 

 25 

 30 

 41 

 44 



* The reactions {-\ — = positive, negative, and indifferent respectively) are 

 based on the movements of ten larvae given five trials each with an exposure of 

 thirty seconds. Between trials — taking larva no. 1 first, then no. 2, etc., through 

 the serie.s — each individual was kept separate in a closed receptacle. 



An inspection of table 5 shows that in Lucilia caesar the lowest 

 directive intensity is 0.00176 CM. and for Calliphora vomitoria, 

 0.00705 CM. This difference in sensitiveness was quite evident 

 in all experiments in which both species were involved, L. caesar 

 responding more readily and being more active than C vomi- 

 toria. 



Below the respective minimum directive intensities, light has, 

 however, a dynamic effect until an intensity of 0.00007 CM. is 

 reached, when there is neither a directive nor a dynamic effect. 

 The larva under such conditions remained perfectly quiet, as 

 though in the dark. This is illustrated by fig. 24, which shows 

 the tracings made by larvae in total darkness. There is a certain 



