BY R. J. TILLYARD. 



737 



in their famous work on the Wing- Venation of Insects,"^ did not 

 deal with the Myrmelponid(v, but tliey succeeded in photograph- 

 ing the tracheation of the pupal wing of one of the Hemerobiidce. 



^^^^^^^^^^m 



Text-fig.l. — Wing-tracheation from the forewing-sheath of a pupa of an 

 Hemerobiid, much enlarged. Adapted from Conistock and Needham. 



They happened to hit upon a form, tlierefore, in which the vena- 

 tion is remarkably easy to determine, since it agrees in almost 

 every detail with the pupal tracheation preceding it. This can 

 be seen from figs. 1-2. All the main veins of the imaginal wing 

 follow the curves of their _, 



C 



corresponding tracheae, ex- 

 cept for a certain amount 

 of secondary fusion at their 

 bases; (the trachea? are, of 

 course, quite separate at 

 their bases, owing to the 

 greater breadth of the wing- 

 sheath). It is thus pos- 

 sible, in the case of Heme- 

 rohius, to indicate, without 

 any shadow of doubt, the 

 number and limits of the 

 radial sectors (Rs), the posi- 

 tion of the two-branched media (M), of the two-branched cubitus 

 (Cu), and of the three-branched analis(lA, 2 A, 3 A). Such a 

 complete agreement between tracheation and venation indicates, 

 of course, a great lack of specialisation in the latter, and suggests 



Text- fig. 2. 

 Wings of Hemerohias nitidulus{ 

 Adapted from Handlirscli. 



8). 



" The Wings of Insects," American Naturalist, 1898, xxxii , seven parts. 



