6 Journal New York Entomological Society. [Vol. xiii. 



chitin which takes a faint stain with hematoxylin. This chitin is 

 especially pronounced around the wing buds, which it entirely sur- 

 rounds, at first more or less completely filling the cavity between the 

 wing and the hypodermis. 



(a 7 ) Formation of the Veins. — At about the beginning of the 

 prepupal period, or shortly before, the vein cavities begin to be 

 formed. Several branches arise from the trachea at the base of the 

 wing and push into the wing pad, the two layers of the basement 

 membrane separating as the trachea enters (Fig. 38). At the same 

 time that the tracheae enter the wing the tracheoles uncoil and accom- 

 pany the tracheae. This manner of the formation of the veins, which 

 I have observed in T. plastographus and D. valens and also in Bruchus 

 sp. and the Pepper beetle, differs from the account of Tower, who 

 found that the cavities were formed before the tracheae develop and 

 enter the wing, whereas, so far as I have been able to observe, the 

 development of the two is coincident. 



3. The Tracheal System. 



According to Comstock and Needham, working on Hippodamia 

 13-punctata, there are in the wings of Coleoptera, as has been so often 

 shown to be the case in the Lepidoptera, two systems of tracheation, 

 a temporary system of tracheoles, and the permanent wing tracheae, 

 which develop after entering the wing a system of tracheoles of their 

 own ; the temporary system of tracheoles being much less highly 

 developed than in the Lepidoptera. The permanent tracheae enter 

 the wing during the last larval stage, when the wing is well developed 

 and at the beginning of its rapid extension. 



While they found the two distinct systems in the Coleoptera, they 

 found that in wings developing externally like those of a dragon- 

 fly, "the principal tracheae pass out very early into the wing bud, 

 branching freely and forming by multitudinous terminal anastomoses 

 a network of capillary tracheoles," no temporary tracheoles being 

 found. They believe that the development of the latter is due to and 

 depends on the confinement of the wing within narrow quarters inside 

 the body and to its small size. Their observations on the Coleoptera 

 were corroborated by the researches of Tower. I have found evidence 

 leading me to the conclusion that there is no fundamental difference 

 between the development of the tracheoles and that of the tracheae, 

 but that the two systems merge into one another. I will reserve this, 

 however, for a later communication. 



