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TEXT-BOOK OF ENTOMOLOGY 



they become drawn out with this membrane, at the time of exuvia- 

 tion, i.e. of pupation, and are drawn out of the neighboring spiracle. 



"This is a very curious phenomenon, which can be verified experimentally: 

 if we cut off the wing, while sparing the larval integument around the thoracic 



FIG. 146. Full-grown larva of Pltris ItramficcB, opened along- the dorsal line: d, digestive 

 canal; x, silk-gland ; (/, brain; xl 7, prothoraoic stigma; ntlV, 1st abdominal stigma; u, <i', germs 

 ( buds) of fore and hind wings ; /i, bud of prothoraoic segment ; those of the third pair are concealed 

 under the silk-glands ; /-///, thoracic rings. After Gonin. 



spiracles, we preserve the two tracheal systems ; the same operation performed 

 after complete removal of the larval skin does not give the secondary tracheal 

 system." (Gonin.) Deceived by the appearance of the tracheoles while still 

 undeveloped, Landois and Pancritius, who have not mentioned the drawing out 

 of the capillaries of the larva, affirm that they are destroyed by resorption in the 

 chrysalis. 



