206 



THE MONTHLY BULLETIN. 



and .4 mm. in width. Compared with the second stage, it has in- 

 creased in length in the proportions of 7 to 5 and in Avidth 13 to 7. 

 The length of the head has increased in the proportions of 6 to 5, and 

 the width 5 to 4. The mandibles are larger and the oral ring increases 



Fig. 64. — Third stage larva of Callie- 

 phialtes sp. Greatly enlarged. (Orig- 

 inal.) 



Fig. 65. — CalUephi- 

 altes sp. Outline of 

 mandibles. Enlarged. 

 ( Original. ) 



in thickness. The third stage is shorter than the preceding, according 

 to our observations, and at a temperature of 60° F. this averaged thirty- 

 eight hours and varied from twenty-four hours to fifty-three hours. 



The Fourth Stage Larva. (Figure m.) In the fourth stage the 

 liead of the Jar\a of this parasite does not yet assume the characteristic 



Fig. 66. — Fourth stage larva of Callie- 

 phialtes sp., showing third moult skin at- 

 tached to anal segment. Greatly enlarged. 

 ( Original. ) 



Tchneumonid type. The oral ring is a brownish color and the mandibles 

 ai-e larger than in the preceding stages. The head is still of a wdiitish 

 color, the first body segment and the two anal segments are also 

 whitish. The abdominal contents have taken on a dull brownish color 

 and the urates are still fairly conspicuous. The curve of the body 

 becomes more pronounced. The length of the larva averages 3.7 mm., 

 varying from 3.5 mm. to 4 mm., the width averaging 1.2 mm. The 

 head varies in width from .41 mm. to .5 mm. and the length from .32 

 mm. to .5 mm. The proportionate increase in length of the larva over 

 the third stage larva is about 4 to 3, and in width 4 to 3. The pro- 

 portionate increase in the length of the head is very small, if any, but 

 in width it is about 8 to 9. The time of the fourth stage at a mean 

 of 65° F. was forty-nine hours. 



The Fifth Stage Larva. (Figure 67.) With the casting of the 

 fourth moult skin the head of the larva assumes the Tchneumonid type 

 and is retracted to a great extent into the fleshy first body segment. 

 The mandibles and oral ring are much heavier than in the other stages. 



