Tue Brotocy or ErHypRA SUBOPACA LOEW 571 
segment, and, as with the third and fourth pairs, the tip of each branch 
from one side meets its fellow from the other to form a false commissure. 
Finally, in the tenth segment is the eighth pair. Both this pair and the 
preceding one supply the convoluted mid-intestine. 
Of the outer branches, those of the first pair arise in the fourth segment. 
They turn inward, extend forward as far as the first segment, and divide 
into several branches there to supply the muscles of the cephalopharyngeal 
skeleton. In the fifth and sixth segments arise, respectively, the second 
and third pairs, which supply the imaginal disks of the wings, halteres, 
and mesothorax. These branches divide into sub-branches. The sub- 
branches of the second pair go to the third segment and end underneath 
the cephalopharyngeal skeleton, either with or without further ramification. 
The sub-branches of the third pair are connected with different structures 
within the body cavity. One of the sub-branches of this pair connects 
with corresponding tracheal branches of other segments to form the 
slender ventral trunk. From the fourth pair to the eighth, inclusive, 
each branch consists of four sub-branches, one arising from the dorsal 
trunk, one going to the ventral trunk, one penetrating the fat bodies 
and ending in the dorsal body wall, and one passing mesad underneath 
the dorsal trunk and supplying the alimentary canal. In the sixth pair 
there is a prominent white tracheal body in each inward-turning sub- 
branch. The function of these bodies is perhaps hydrostatic. The ninth 
pair is similar to any of the preceding ones, except that one of the sub- 
branches, instead of attaching to the alimentary canal, goes to the lateral 
body wall. The branches of the tenth pair are very strongly developed. 
They arise in the caudal process and extend forward as far as the eighth 
segment, to connect with the alimentary canal. Each branch has two 
large sub-branches, one anterior and one posterior. The anterior sub- 
branch goes to the eleventh segment and is attached to the hind intestine. 
The posterior sub-branch subdivides itself again, sending out an anterior 
sub-branch to supply the twelfth segment and a posterior sub branch to 
extend to the end of the caudal process. The strong development of the 
last pair of the outer branches, as Tragardh considers, is due to the 
elongation of the hind intestine, but, in addition to this, the writer is 
inclined to think that the elongation of the caudal process, when the 
larva grows, must be a cause also. 
