54 CLAUDE FULLER. 



The duplication of principals is very frequent in Calo- 

 termes, where all have been found in this condition except 

 the radial. It is also common enough in Cry p to term es. 



VId. Reduction of Teache.?*:. 



In the final wings of Calotermes durbanensi s numerous 

 abnormalities of the venation are directly traceable to pre- 

 existing extra principal tracheae. As evidence of this is 

 also to be found in the wings of other species, one is justified 

 in concluding that the predecessor of the termite wing was a 

 tracheated organ into which many more principal tracheas 

 penetrated than is ordinai-ily regarded as the full comple- 

 ment, and perhaps the production of these exceptional 

 tracheae may be regarded as reminiscent of an ancient 

 ancestor. 



In an earlier section it has been shown that the development 

 of the tracheae of the wing-sac occurs in an orderly sequence. 

 Making allowance for reductiou in area, it is equally true that 

 both the gradual reduction of some principal trachea? and the 

 loss of others takes place iu an orderly sequence ; this 

 reduction may be described as a gradual retirement along 

 the line of advance. 



Of the principal trachete, the sub-costal and the anal are 

 the latest to develop, aud should, on the foregoing premises, 

 be the first to disappear. However, as a rule, it is the post- 

 costal that is earliest lost, then the anal, and, lastly, the 

 sub-costal ; this slight derangement of the sequence being no 

 doubt due to the narrowing of the basal area of the wing. 



The post- costal is quite extensive and many-branched in 

 Hodotermes karrooensis and H. transvaalensis. In 

 H. viator it is weaker and less branched. In Calotermes 

 and Cryptotermes it is, comparatively speaking, Aveakly 

 developed and but rarely branched, and is more atrophied 

 in the hind wing than the fore wing. It is a shortened and 

 simple trachea in Rhinotermes put or ins; reduced and 

 inconstant in Termes natalensis; and, in Microtermes 



