TDs Cu1H PING 
In the dorsal trunk taenidia are present in the parts anterior to the 
first outer branch and posterior to the sixth outer branch. These parts 
are distinguished from the rest by the dark brown color. In the parts 
where taenidia are absent the color of the tracheal trunk is silvery white. 
There is an absence of taenidia in four places in each trunk, three of 
which are close behind the sixth, seventh, and eighth outer branches, 
respectively, and-.one is between the ninth and tenth outer branches. 
As already mentioned, the ventral trunks are a secondary make-up 
through the connection of the sub-branches from the dorsal trunks, so 
they are much more slender and delicate than the, dorsal. In each trunk 
the anterior end ramifies in the fourth segment underneath the cepha- 
lopharyngeal skeleton. From the fifth to the eleventh segment, inclusive, 
there is an inner branch in each segment. This inner branch ramifies in 
the prolegs. In the twelfth segment the anterior end of the trunk ends 
with the alimentary canal. The ventral trunk has two outer branches in 
each segment from the fifth to the tenth, inclusive. All of them go to 
the latero-dorsal body wall (Plate LIV, 8 and 9). 
The fine branches that penetrate the subesophageal ganglion are con- 
nected with the ventral trunk. Such connection can be best seen from 
the lateral aspect, when the specimen is fresh and the trachea are filled 
with air. 
The nervous system.— The nervous system of this form in general 
differs very little from that of the larva of Musca. The nervous center 
consists of a boat-shaped ganglion and two prominent cerebral lobes. 
Between the latter pass the esophagus, a pair of tracheae, and the dorsal 
vessel. Cephalad to the lobes are two major cephalic imaginal discs, 
each of which is connected antero-laterally with an optic stalk. The 
only difference here from the larva of Musca domestica is that there is 
no such problematical cellular structure as was figured by Hewitt (1908), 
situated close above the major cephalic disks and the cerebral lobes 
(Plate LIV, 10). 
The nerve branches I and II arise from the cephalic part of the 
central ganglion, one of them (I) going to the cephalopharyngeal mass, 
and the other (II) going to the muscles of the lateral pharyngeal sclerites. 
There are three pairs of nerve branches (a, b, and ¢) arising from the 
stalks of the prothoracic and mesothoracic disks. In addition to these, 
nine pairs arise from the lateral and caudal parts of the ganglion. From 
