s 



72 PROCEEDINGS ENTOMOLOGICAL SOCIETY 



cocoon and deposits these globules upon its outer surface, where 

 they are fastened by silk from the larva's mouth. 



The cases which have been cited, although few, are of such 

 widely different insects that it seems almost certain that in 

 this inflation of the digestive tvibe with air we have a principle 

 which is fundamental in the moulting process of insects. If 

 one stops to reflect it will appear quite obvious that something 

 besides mere muscular exertion is necessary to liberate the 

 insect from its exuviae. At the time of emergence the chitin is 

 soft and therefore cannot offer sufficient resistance for any 

 great muscular exertion. Thus at this time the insect is hardly 

 capable of making full use of its muscles. Even if one allows 

 for the lines of weakness, which are already determined in the 

 pupal shell, it will still be admitted that it takes a considerable 

 force to rupture, for example, the chrysalis of a moth. An 

 insect issuing from its pupa hardly gives the impression of 

 great muscular vigor. This subject well merits further inves- 

 tigation. Thus in the case of Lepidoptera and Diptera the 

 digestive tract is closed during the pupal period ; by what means 

 does it become inflated with air? 



SUPPLEMENTARY NOTE. At Dr. Howard's suggestion I 

 have examined the work of Maillot and Lambert on the silk 

 worm for further information on the process of ecdysis in the 

 Lepidoptera.* The description given by them of the eclosion 

 of Bomby.v niori is manifestly faulty and the interpretation of 

 the processes involved is incorrect ; yet it shows that in this case 

 also the swallowing of air is an important factor, if not in the 

 escape of the imago from the chrysalis, at least in the expan- 

 sion of its wings. The authors incorrectly state that the wings 

 are expanded by the forcing of air into the veins. What is 

 here important is the observation that while the wings are 

 being expanded the crop is being rapidly filled with air. It is 

 perhaps best to quote the original passage : 



En meme temps que les ailes s'etenclent et que les teguments devien- 

 nent sees, le jabot, a 1'interieur du corps, vide du liquide qu'il contenait, 

 se gonfle d'air rapidement ; aussi l'appelle-t-on sac a air. Les innom- 

 brables trachees qui se ramifient dans 1'abdomen se replissent aussi 

 d'une grande quantite d'air. 



The last statement, that the air taken into the crop serves 

 to fill the tracheae, is of course an assumption and it is clear 

 that we have here the process previously discussed. 



*Traite sur le ver a soie du murier ct sur le murier, p. 293 (1906). 



