82 Annals Entomological Society of America [Vol. VI, 



rior branch of the following trachea. There is also a suggestion 

 of splitting near the base of the anterior branch. The third 

 is two-branched with the anastomosis as noted. The fourth 

 is two-branched, the tracheae separating very close to the base 

 of the wing. The last is also two-branched with the branches 

 coalescing at their extremities. 



The relationship of these treacheae with the corresponding 

 wing veins is evident. Their identification as regards the 

 homologies of wing veins in general is not so simple a matter. 

 For this reason the veins as dependent on these tracheae will be 

 discussed in order, beginning at the costal margin. 



FORE WING 



Costa 



Costa never appears as a separate vein in the adult wing. 

 It was some time in the course of this study before sufficient 

 data was obtained to determine exactly what had become of 

 this vein, since most of the preparations failed to show a cor- 

 responding trachea in the nymphal wing. Finally however, 

 an examination of younger stages of various species furnished 

 the solution. In Thelia bimaculata (Fig. 3) it was found that 

 costa was represented in the nymphal tracheation but never 

 entered the wing for a sufficient distance to have a place in the 

 adult structure. In most individuals the atrophy was greater 

 than that shown in the figure. In Telemona ampelopsidis 

 (Fig. 4) the treachea is twisted around the subcosta and no 

 doubt coalesces with it in the vein which afterwards encloses 

 them. In Ceresa borealis (Fig. 5) the trachea extends farther 

 into the wing but is not so well developed and probably has no 

 effect on the venation. In Vanduzea arquata (Fig. 6) much the 

 same appearance is shown except that the trachea is stronger 

 and lies nearer the margin of the wing. 



To sum up then, the trachea which usually precedes the 

 costal vein is represented in the nymphal structure but the vein 

 itself is not found in the adult wing. In such genera as Thelia, 

 Acutalis and Glossonotus^^ in which a slight membrane is found 

 cephalad of subcosta but no thickened ridge is present, the vein 

 is probably atrophied^'^. 



14. All forms mentioned are figured either tlirough the text or at the end of 

 the discussion. The figures of adult wings are drawn to show the coalescence of 

 tracheae to form a single vein when such has been the case. 



15. This is no unusual condition with costa. Comstock and Needham say 

 (Wings of Insects, p. 858). "Its (costa's) trachea is often atrophied, probably- 

 owing to the disadvantageous position of its base in relation to air supply, as we 

 have hitherto indicated." 



