76 CIAUDE FULLER. 



the small cross-ribs already alluded to. The main tracheic 

 and their offsets do, however, lengthen considerably. Often 

 the terminals of the radial, medial, and cubital travel for 

 a considerable distance around the margin, and a remark- 

 able extension of the cubital tip is shown in fig. 142 (PI. IX). 

 This wing-sac also illustrates the almost regular habit of the 

 cubital offsets to dichotomise and for the branches to inter- 

 mingle or turnback into the wing-sac. 



The basal arrangement of the trachea? is similar to that of 

 Calotermes. This is shown, as seen in a preparation, by 

 fig. 140 (PI. IX). 



In both fore and hind wing-sacs the post-costal and anal 

 are present. In the younger nymphs the trachea^ first pene- 

 trate and develop in the Aving-sac in more or less straight and 

 parallel courses. In fig. 186 (PI. IX) only the radial, medial, 

 and cubital have developed. Two later stages are represented 

 in figs. 137 and 138 ; both illustrate the late development of 

 the anal. The radial and cubital branch about the same time ; 

 and, after this takes place, the tip of the medial inclines 

 towards that of the radial, fig. 138 ; as the wing-sac grows, 

 they extend, closely applied to each other, to and around its 

 jipex. When applied to the radial the medial is usually the 

 more tenuous of the two. It may run quite evenly with it, 

 fig. 139a ; or entwine it, fig. 139b ; or leave it abruptly, 

 fig. 139('; or produce a straight or sinuous offset, figs. 139i) 

 and E; or an atrophied offset, fig. 139f. Sometimes the 

 medial or its main offset bears one or several very fine 

 branches, fig. 139g. 



Further, after meeting the radial the growth of the medial 

 may stop, or vice versa, the radial may grow no further. In 

 this event the medial assumes the function of the radial, simu- 

 lating it 1)y sending a series of branches to the outer margin. 

 Abnormal schemes of tracheation were not met with in the 

 long series of wing-sacs studied, other than the peculiar 

 development of a trachea from the radial root shown in 

 fig. 153 (1*1. X). The most unusual scheme was that reproduced 

 by fig. 154. 



