THE VARIATIONS DURING LIFE 



ii i 



Metabolism During the Pupal Life of Insects. 



When the metamorphosis from larva to chrysalis begins, an insect 

 is a completely organized animal provided usually with a consider- 

 able reserve of fat and ceasing to take food and make muscular 

 movements. In this animal a histolysis takes place which, though 

 very different in extent and rapidity in different forms, will in extreme 

 cases (flies, butterflies) reduce the organism to few and small heaps of 

 single cells and a yolk of nutritive material. From the cells the 

 organism of the imago is developed by a process which bears a very 

 close resemblance to embryonic development. 



Sosnowski [1902], Weinland [1906], and Tangl [1909, i] have 

 made investigations on the chrysalides of flies (Musca vomitoria> 

 Lucilia ccssar, Ophyra cadaverina}. They have found that the 

 respiratory exchange (CO 2 production) is high at first, then falls 

 for some days, and finally rises again. I give (Table XXIII) as the 

 best example the figures obtained in one of Weinland's series of experi- 

 ments on 305 chrysalides of blow-flies weighing 2 2 '6 gr. at tempera- 

 tures varying irregularly between 1 6 and 20. 



TABLE XXIII. 



Towards the end of the pupal period muscular movements take 

 place leading up to the opening of the cocoon and the appearance of 

 the fly. The metabolism measured during the last days is therefore 

 not purely standard metabolism. 



Tangl also ascribes the large metabolism in the initial period of 

 the pupal life to muscular movements. Weinland [Op.] denies 

 that such movements take place, and thinks that the histolytic pro- 



