art. 21. DRAGONFLIES OF BURMA AND LOWER SIAM—LAIDLAW. 7 
The first two species are quite distinct from each other, both 
belong undoubtedly to the Brachytron series, and they are probably 
not congeneric. For convenience sake only I refer both to Cephal- 
aeschna. 
One of these “ Cephalaeschna,’”’ which is represented by some 4 
specimens, all probably in the last or penultimate instar, has the 
appendix dorsalis very definitely bifid, ending in a pair of pointed 
processes, whilst in the other species, of which I have also several 
examples, the same structure is simple. 
I was fortunate enough to be able to mount a wing of the former 
species which showed very clearly the details of the tracheation. A 
very interesting point distinctly shown in this specimen is that the 
fork of Rs is not preceded by a fork in its tracheal precursor. 
The trachea, however, give off on its anal side several (four or five) 
small but well-marked branches, which run to the anal margin of 
the wing. From each of these a fine twig is given off nearly at right 
angles to it; these twigs together form a line of delicate tracheation 
running parallel to the main trunk of Rs, and along their course the 
chitinous supplement (Rspl) is laid down. A precisely similar con- 
dition obtains with regard to M, and its supplement in this wing. 
In the case of the larva of the second species of ‘‘ Cephalaeschna”’ 
I have not been able to make out anything of the tracheation. 
Turning now to the larva of Aeschna ornithocephala, a specimen 
in the last instar fortunately showed the tracheation with beautiful 
clearness. I was surprised to find in this specimen that both M, and 
Rs each give off a strong branch, practically a fork near the level of 
the beginning of their respective supplements, and that this fork fol- 
lows the course taken by the supplement in either case; giving off in 
- addition three or four branches to the hinder margin of the wing, 
whilst the anterior branch of the fork after running toward the apex 
of the wing turns analward at the level of the small imaginal “ fork” 
without giving off any branch of importance. So that in this form, 
and presumably in other Aeschnas the median and radiul ‘‘supple- 
ments’’ should be termed rather the median and radial branches. 
Tillyard’s figure (p. 44, fig. 17-A-B) of the tracheation of Aeschna 
brevistyla in the Biology of Dragonflies shows the forking of M, but 
he does not figure enough of the wing to show the fork of Rs. 
Lastly, in Anaz the tracheation has been in part figured by Need- 
ham in his Genealogic Study. He shows there in a beautiful micro- 
photograph of the larval wing of Anaz junius Drury, that the median 
supplement is formed as in ‘‘ Cephalaeschna” species along a line of 
secondary tracheal twigs derived from branches of M,; and the ra- 
dial supplement is formed in a similar manner, as I have been able to 
satisfy myself by an examination of larva of Anaz ephippiger. 
