258 



BEVERLY WAUGH KUNKEL 



found difficult to measure the length of the larvae very accu- 

 rately because of their consistency and the protrusion of the 

 mouth parts. The length was obtained with dividers and a milli- 

 meter scale. It was soon found, however, that sufficient accu- 

 racy was not possible by this means, and so in later experiments 

 the length of the pupae was used as an index of the effect of special 

 feeding on the growth of the larvae. By means of micrometer 

 calipers it was possible to measure the pupae to .001 inch. 



A number of observations was made to determine the effect 

 of Jthyroid feeding on the length of the larvae. From these, the 

 following have been selected because of the completeness of the 

 data regarding the flies. In all the observations on the length 

 of the larvae there was an abundance of food present so that 

 effects are not due to insufficient food. Unfortunately, I did not 

 identify the adults, but judging from the characters of the larvae, 

 there is no doubt but that we are dealing with Lucilia. 



Measurements were made of larvae varying in age from two to 

 eight days and in all these cases except in the youngest larvae of 

 two days' age, the muscle-fed larvae were slightly longer than the 

 thyroid-fed. Except in the eight-day larvae, the difference in 

 length is rather insignificant. Great care was taken in the meas- 

 urement of the larvae not to estimate the thyroid larvae low and 

 the muscle larvae high. 



The results are shown in the following table : 



TABLE 1 



Shoivi7ig the effect of thyroid feeding on the average length of larvae of 



different ages 



Age of larvae in days 



Egg mass number 



Average length in mm. thyroid-fed. 

 Average length in mm. muscle-fed. 



4 



13.4 

 14.9 



Table 2 indicates the distribution of the larvae in egg mass No . 

 5. In this experiment, after seven days of feeding twenty larvae 

 from the thyroid and twenty from the muscle, chosen at random, 

 were measured after killing with boiling water. 



