SOUTH AFRICAN TERMITES. 71 



departures, and there is no evidence to show that the compli- 

 cated arrangements, to be discussed, are due to physical 

 injuries. The following series of abnormal schemes are 

 selected to indicate the range of departures from normal 

 development, and are arranged from the more simple to the 

 more complicated. 



Fig, 95 (PL VII) represents an abnormal medial which has 

 developed two strong branches, both of which accompany 

 their parent stem to the apex of the wing, but cross one 

 another in their progress there. The crossing of tracheae is 

 very frequent in the case of branches from principals, and 

 principals themselves often cross. In fig. 96 (PL VII) the 

 medial is seen crossing the cubital and invading its field. An 

 event of this sort usually leads to the part atrophy of one of 

 the trachea), in this case the media, and the over-development 

 of the other. It results in the formation of large elongate 

 cells in the final wing and those illustrated in figs. 118, 120 

 (PL VIII), 125, 127, 128, 130 (PL IX) seem to owe their con- 

 dition to this factor. These wings are much like others, 

 figs. 113 (PL VIII), 119 (PL VIII), but here the median cells 

 may have arisen from the coming together of tracheae (as in 

 Cryptotermes) and not from crossing. 



Fig. 97 (PL VII) illustrates a fairly simple case of a dupli- 

 cated trachea, the medial, and is selected to show extra 

 features ; i.e. the crossing of the two and the part atrophy 

 of one. Fig. 98a (PL VII) illustrates another case of a dupli- 

 cated media. It differs from the former insonmch that the 

 duplication seems a secondary condition, the outer medial 

 appearing as a growth from the inner, fig. 98b (PL VII). 

 In this case the two extended through the median field and 

 reached to the wing apex. Fig. 99a shows a simple duplica- 

 tion of the cubital trachea, and fig. 99b how the extra trachea 

 originates opposite the seat of the anal. In this case the two 

 tracheae maintained a cubital character ; that is, both had 

 offsets to the inner margin of the wing-sac, as is the habit 

 of the pseudo-media and cubitus with Hodotermes and 

 other species to be mentioned later. 



