SOUTH AFRICAN TERMITES. 47 



Except for the extra pair of longitudinal trunks and the 

 X-trachea, the characters of the stem of the thorax and 

 abdomen are agreeable with those of the Metatermite 

 form ; but the cephalic arrangement is (juite different. 



The simple U-shaped trachea formed by the extensions of 

 the spiracular trunks into the head is wanting, whilst the 

 continuations of the dorsal longitudinal trunks are more 

 amply developed. 



The spiracular trunks projecting into the head cavity each 

 have a tree-like form, and their stems are linked together by 

 a transverse commissure placed Avell back so as to give an 

 arrangement resembling the letter H. In the region of the 

 labium each trunk subdivides into three principal stems whicli 

 supply the mouth-parts, fig. 21a (PI. IV). Upon the whole, 

 their arrangement is like that seen in T. natalensis, but 

 the paired trachere of the labium arrive within the clypeus 

 by a more indii-ect route. They first bend outwards more or 

 less at right angles to the parent stems, travel behind the 

 eyes, and then upwards into the dome, bending sharply 

 inwards to the clypeus ; here they turn forward at a right 

 angle and pursue a remarkably straight course into the 

 labrnm. 'I'hey may be said to traverse the inside of the 

 head capsule from their point of origin to where they turn 

 out of the clypeus. As in the Metatermite form, so in 

 this the spiracular tracheee are connected with the main 

 dorsal trachege by upright commissures, but these are both 

 very incurved and C-shaped. As development proceeds they 

 become approximated and then fuse at the point of contact to 

 form ati DC-shaped combination. 



In more mviture nymphs of Cryptotermes, Calotermes, 

 Hodotermes, and Rhinotermes there is a decided Y-shaped 

 trachea between the two dorsal tracheae (those which have 

 their terminations in the antennse), the arms of the Y being- 

 attached at the same points as are the vertical C-shaped 

 trachcfe just described, fig. 21b. This middle trachea 

 undoubtedly originates in Cryptotermes from two trachea?, 

 each an inner basal branch of the dorsal tracheas. These 



