6o William B. H 



erjns 



Sarcophaga sarraceniae endured the experimental conditions 

 far better than Lucilia as was evident from the number of imagines 

 resulting in each case — 90 per cent in the former and only i6§ per 

 cent in the latter, including the set which perished entirely. The 

 greatest mortality occurred during the period between migration 

 and pupation, though a good portion never completed the period 

 of pupation after having entered it — about 40 per cent in Lucilia 

 and about 6 per cent in Sarcophaga. 



In order to secure a fair weight it was necessary to brush each 

 larva clean with a camel's hair brush. This great amount of 

 handling had practically no effect on Sarcophaga, which are quite 

 hardy, but on the other hand Lucilia were seriously affected.^ 

 However, in the latter case it is well worth noting that the sur- 

 vivors are very near the mode of normal frequency for larvae at 

 migration, for pupae and for imagines {cf. normal frequency 

 curves. Fig. 7, with growth curve, Fig. 2). 



This growth as indicated by the curves was checked by the 

 growth of larvae, both in time and weight, feeding on fish out of 

 doors under normal conditions, and it was found that the time is 

 the same, and that the average weight of migrating larvae varied 

 but 0.5 mg. This difference would, undoubtedly, have been 

 entirely wiped out had a larger number of individuals been used. 



Discussion of Curves 



Lucilia caesar (Fig. 2) : The figure shows a curve derived from 

 a set weighed every two hours for the first twenty-four hours after 

 hatching, every four hours during the following twenty-four, every 

 six hours for the next twelve, etc., as indicated in Table II, column 

 2, according to which this curve is constructed. The curve begins 

 with the weight often eggs (i mg.) This egg stage is represented 

 by the dotted line and covers a period of about twelve hours. At 

 this point the larvae hatched and were weighed three hours after 

 the emergence of the first individual with a weight of 4 mg., for 

 twenty or 2 mg. for ten, as shown by the curve. The average 

 increase in weight during the first three hours is 50 per cent which 



'This may not have been entirely due to the handling; the same mortality for this species may 

 possibly exist in natural conditions. 



