Ecological and Experimental Study of SarcophagidcB 71 



parison with the normal frequency curve for larvae shows that the 

 aberrent forms beyond the optimum shown in the curve are either 

 just within the above mean or just beyond. It is also interesting 

 to know that 63 per cent of the total number of dead larvae are 

 beyond 45 mg. in weight. 



Series 9 — It will be seen that these larvae migrated five hours 

 sooner than other migrating individuals, but that the weight on 

 the other hand is nearly equal to the optimum. This corroborates 

 the statement made above that some individuals eat more rapidly 

 than others, and again this series augments the evidence in favor 

 of an optimum weight. 



Series 2 — In this series the optimum time limit for feeding is 

 practically reached, but, since these larvae were still feeding at 

 sixty hours, the flesh was taken away, and we see that the optimum 

 weight had not yet been reached by several milligrams. This 

 indicates again, when compared with series 9, that certain larvae 

 feed faster and reach the optimum more quickly than others. 



Series 3 — Food taken away after feeding fifty-four hours. 

 Pupation takes place readily and promptly and adults emerge on 

 time, but are short weight and small in size. 



Series 4 — Food taken away after feeding forty-eight hours. 

 Pupation takes place as above, also same for imagines. For those 

 series below the optimum down to and inclusive of forty-two hours, 

 the average time between migration, or in these cases time of taking 

 food away, and pupation, is very much more regular and nearer 

 the normal time, /. e., about four days. This might be expected, 

 since in the normal series we have many larvae which have gone 

 beyond the optimum weight and pupation is consequently retarded. 

 On the other hand, in the series just mentioned the larvae are 

 practically all within the optimum, consequently the time for the 

 entire life history of each individual conforms more closely to 

 the normal and there is no dragging out of the prepupal period. 



Series 5 — In this series from which the food was taken away at 

 forty-two hours, all the original weighed larvae died because of an 

 accident. As a result the pupal weight is not given, but the 

 weight of the adults was taken from the accessory series. The 

 number of individual larvae in the accessory series was not taken, 

 but only thirty-nine pupae resulted, and from these only thirty- 



