BY R. J. TILLYARD. 107 



scries of descending branches arranged more or less pectinately; 

 and probably also in the older Trichoptera, though the homologies 

 in this Order are not yet quite clear, owing to the absence of 

 the preceding tracheation in the pupal wing. 



((>) The anal furrow (aj ') is very definitely marked, and quite 

 distinctly separates the cubitus from the first analis. 



(7) There are three separate anal trachea) present, none of 

 them branched. Trachea 2 A tends to bend towards 1A dis- 

 tally, but docs not meet it. Trachea 3A is very short, and 

 descends to the wing-border just beyond the distal end of the 

 jugal lobe. 



The above interpretation is so obvious that it can scarcely be 

 questioned. Nevertheless, Professor Comstock, in his recent 

 book already quoted (3), while figuring the tracheation, as far as 

 he could make it out in the imago, as essentially the same as 

 that here figured for the pupa, gives a different interpretation to 

 the limits of the cubital and anal trachea?. The reasons for this 

 appear to be two: — 



(1) Professor Comstock starts with the assumption that the 

 cubitus was originally only two-branched. This assumption is 

 applied to the Aquatic Trichoptera, where it appears to fit, and 

 then the tracheation of the Micropterygina is interpreted along 

 the same lines. In order to do this, it is asserted that trachea 

 1A has migrated forwards and become fused with Cu basally; 

 but no proof is offered of such an astonishing specialisation, in 

 so archaic a group as the Micropterygidce. 



(2) In many Lepidoptera, the original dichotomy of Cu into 

 Cuj and Cu 2 occurs very close to the base; and, as is usual in 

 this Order, the tracheae split back even further than the veins; 

 so that, in the higher groups, the division of Cu may take place 

 almost or quite on the alar trunk trachea. This lenOs support 

 to the idea that there are here two main trachea 1 , Cu and 1A. 

 Against this, it may be mentioned that, firstly, the anal group 

 of three tracheae can always be made out, arising very far away 

 from these other two; secondly, that, in many cases, especially 

 in the older families, this splitting hack does not reach as far as 



