196 DEVELOPMENT OF THE WING-VENATION OF ODONATA, 



up white and unpigmented, with large patches of black pigment 

 in each separate cell. 



For our general study, I will now select the lai'gest as well as 

 the palest of all the larvaj examined, that of Caliayrion billiity- 

 hursti Martin. This very beautiful larva is of a bright green 

 colour, and its wings are pigmented uniformly and lightly all 

 over. I was, unfortunately, unable to study any of the earlier 

 stages of this or any other larva, owing to the lateness of the 

 season when I first started (September). A complete study of 

 the Caliayrion nymph will, I hope, be undertaken next season, 

 with a view to determining the ontogenetic development of Rs. 



A very clear photograph of the complete hindiviny is given in 

 Plate xi., fig. 14, while Fig. 1 of Plate xiii., gives a much more 

 highly magnified photograph of the most important parts. From 

 these and from the diagram in Plate xii., fig.l, it will be seen 

 that, in Caliayrion, as in all the Anisoptera, trachea A fuses with 

 Cu as far as the anal crossing (Ac). This can also be seen very 

 clearly in Anstrolestes, less clearly in ISynlestes; while, in the 

 smaller species, it is often very ditiicult to detect any trace of A 

 at all. This is especially the case with the p7-oioneurini, JVeo- 

 sticta, and Isosticta, in which the whole anal trachea seems to be 

 quite aborted, except that, in one or two specimens, I have 

 detected a very fine and short basal portion which fails to reach 

 Cu. However, in all cases Ac can be detected, though not with- 

 out careful searching in the case of the most reduced forms. 



From this, we must conclude that the anal trachea of the 

 Zygopterid nymphal wing behaves in the same manner as the 

 coi'responding trachea in Anisoptera. Hence, as far as A' and 

 Ac are concerned, the new notation applies to all Odonata. 



The next point is a very startling one, viz., that, in Caliayrion, 

 the anal trachea at the distal end of Ac becomes four-branched, 

 just as it does in Atdsoptei^a (VlsLte xii., fig.l). The branch A, 

 runs basad for a short distance, and along and beyond its course 

 the future secondary anal vein A' of the imaginal wing is clearly 

 marked out as a pale band. A;, and A ^ arise close together under 

 Ac, and run slightly divergingly downwards to supply a quite 

 /airly large a7ial area below. At metamorphosis, these two 



