60 CLAUDE FULLER. 



ings. The point that the marginal ai'ises from a cuticular 

 thickening which does not form about a trachea has been 

 sufficiently emphasised. 



Indeed, for all the rest of the venation it may be laid 

 down as an axiom that where there is no preceding trachea 

 there is no succeeding rib or even ridge. To this it may be 

 added that when the growth of a trachea is weak or when 

 a trachea is undeveloped the succeeding rib is similarly 

 affected. Upon the other hand, it is equally true that 

 thickenings do not necessarily form about all minor tracheae,^ 

 and consequently every such ti'achea does not invariably give 

 rise to a rib in the final hardened wing. 



Variations in the venation are mainly to be traced to the 

 valuation of the tracheation. This is well illustrated in 

 Termes n at ale n sis. For this species it may be stated that 

 the radial may have from to 5 strong inner branches 

 (sectors), the pseudo-medial maybe deeply furcate and many- 

 branched or prncticall}^ simple, the cubital nuiy be over- 

 developed or under-developed. If, of the three, the pseudo- 

 medial is more or less simple, then either the radial possesses 

 sectoi's or the cubital is over-developed. Usually, if the 

 pseudo-medial is well-developed the radial has no sectors, and 

 the cubital presents either a medium or an under-developed 

 condition. When the radial possesses sectors and the pseudo- 

 medial is well-branched, the cubital is under-developed. 



The only other influencing factor seems to me to be the 

 hardening of the wings, to which may be traced breaks and 

 dislocations and actual obliterations. It has to be borne in 

 mind that when finally expanded the termite wing is soft, and 

 days, perhaps weeks, must elapse before it is hardened and 

 rigid. The upper and lower surfaces, never far apart, are 

 drawn closer together, and the process of their union tends 

 to smooth out any rib or part thereof that may be weakl}' 

 formed. So much is this the case that a branch of the 

 cubitus may lose its basal connection and appear as an inde- 

 pendent, from the margin. Obliteration is very marked in 

 T. natalonsis. In this species the freshly-expanded wing 



