THE TRACHEATION OF WINGS 



31 



also be expected. If it is found that any factor causes changes in the 

 tracheal branches to the wings, it may be expected that a similar factor 

 affecting the legs will cause similar changes in the trachea entering the legs 

 and the converse should also be true. 



EXAMPLES OF THE MORE GENERALIZED ARRANGEMENT 



The basal connections of the wing trachecz in a cockroach nymph (Phylo- 

 dromia germanica) , Order Orthoptera. — The condition of the tracheae in the 

 cockroach is very similar to that shown in the diagrams. The connections 

 are as shown in the drawing (Fig. 1 8) which is a dorsal view. The cubito- 

 anal tracheee (cu-a) originate nearer the spiracles than the costo-radial 

 tracheae (c-r) do, but they have the typical connections with the stems of 



Fig. 1 8. — The basal connections of the wing tracheas of a cockroach. Dorsal view. 



the leg tracheas {as and ps) which form the two arms of the Y-shaped leg 

 tracheas. There are muscle tracheae (nit) which go to the coxal muscles 

 but they do not continue into the legs as do the tracheae labeled k and k. 



In the nymphal cockroach there is a single slender dorsal longitudinal 

 trachea (d. It) , on each side of the thorax, lying near the digestive tract and 

 connecting the branches from each of the three spiracles (5^1, spo, and spa). 

 The size and relationships of this trachea are such as to indicate that it may 

 be only an enlarged anastomosis of the branches from the different spiracles. 

 In adult cockroaches the intra-segmental portions of this longitudinal 

 trachea become enlarged to form air sacs. 



The former statement that the wing tracheae of cockroaches are con- 

 nected with the longitudinal tracheae of the thorax has not been confirmed. 

 (Comstock and Needham, Am. Nat. xxxii, p. 88). As the drawing shows, 

 the basal connections of the wing tracheas and the dorsal longitudinal 

 tracheae are quite separate. 



