No. 4-] METAMORPHOSIS OF THE FLAG U'EEVIL. IQI 



a little while enough material for studying its entire metamor- 

 phosis. This material ma}' be excellently fixed in boiling 70 per 

 cent alcohol, and in all stages preceding the imago the chitine is 

 so thin as to interfere but little with section cutting. 



The following conclusions from the foregoing study are be- 

 lieved to be new : 



1. In Mononychus vulpeculus Fabr. there are three larval 

 stages. 



2. The full-grown larva is very degenerate, having only the 

 merest rudiments of antennae, eyes, optic lobes, and salivary 

 glands. 



3. The greater part of the increase in size takes place in 

 about a week after entering the third larval stage ; it is due 

 mainly to fat accumulation. 



4. This brief period of feeding and rapid accumulation of 

 half-assimilated food material is correlated with an extremely 

 long final assimilation period, lasting through months of imaginal 

 life. 



5. There is no real invagination of the buds of wings or leg>. 



6. Many nuclei of fat cells persist after the dissolution of the 

 fat masses, free themselves from these masses, retaining about 

 themselves an investment of protoplasm, associate themselves 

 with developing muscle fibers, and, probably, themselves become 

 the nuclei of new muscle fibers. 



7. Phagocytosis, which was observed only in the fat masses 

 along the sides of the abdomen, occurs only after external 

 metamorphosis is complete. 



