xxxiii, '22] ENTOMOLOGICAL NEWS 301 



less parallel to the tracheae from which they have originated, 

 thus producing the conditions shown in figs. 4 and 5. In fig. 

 4 the anterior of these two branches is now composed of three 

 fine tracheae, the posterior branch is still a single trachea ; in 

 fig. 5 the anterior branch is three-branched, the posterior two- 

 branched. In addition there is another fine branch, the trachea 

 Rs of Needham. This trachea is always but a single fine strand 

 in this instar and crosses over Ml and M2. It can be inter- 

 preted only as a new outgrowth of the radius, appearing for 

 the first time in this instar, and not as the original posterior 

 branch of this trachea which has shifted its position. In fig. 1 

 the radius has no branches ; a larva in which such a condition 

 obtains would in the succeeding instar show a condition such 

 as is represented in figs. 6 and 7. The distal end of the vein 

 has produced a branch so that it is now double at the end, in 

 the same manner as the two branches of R in figs. 2 and 3 have 

 given rise to the two anterior groups of branches seen in fig. 5. 

 In addition, R, in figs. 6 and 7, shows a caudal branch Rs which 

 again is a new outgrowth, appearing for the first time in this 

 instar, just as the small branches which have appeared on the 

 anterior side of both Sc and R are new outgrowths. With 

 respect to .!/, a similar observation might be made on the 

 phenomenon of tracheal branching and on the presence of fas- 

 cicles of tracheae where only single tracheae existed in the 

 preceding instar. In fig. 8 is shown the instar following upon 

 that which is represented in figs. 4-7. The fascicled condition 

 is more evident than in the preceding instar and it is noted that 

 Rs, which was heretofore always simple, has now also produced 

 branches and is composed of a group or fascicle of three 

 tracheae. 



In the wings of Gomphus the same conditions obtain. The 

 usual two-branched condition of the radius of the earliest stage 

 is seen in figs. 0, 11, 12; and in figs. 13, 14, the next stage, in 

 which the two radial branches have been replaced by two fas- 

 cicled branches and in which there is an additional fine branch 

 crossing over .1/1 and .1/2. 



It is evident then, that when a trachea or tracheal branch 



