1929] 
Tracheal System of Pyrausta nuhilalis 
343 
domen there are branches between the branches to the 
ganglia, that run backward, usually one on each side of 
the mid-ventral line, and small branches from these some- 
times enter the commissures. (Fig. 22). Lubbock, (1860) 
states that he found the commissures of adult Lepidoptera 
to be without tracheae, but the commissures in the larvae 
well supplied. 
Occasionally the nerves from the ganglia have short 
tracheae in them. This is more often the case at their 
origin, where a branch from the ganglion-supplying trachea 
often enters them (Fig. 23). Sometimes a small branch 
from the thoracic tracheae, 3 and 5 will go to the nerve trunk 
(Fig. 24). In one specimen the anterior branch from the 
transverse trachea in the seventh abdominal segment sent 
a branch to a nerve originating in the seventh abdominal 
ganglion. (Fig. 25). 
Tracheae to the Appendages. (Fig. 26) 
The tracheae to the mandibles, maxillae and labium have 
been described above. In the section describing the tracheae 
from the prothoracic spiracle the courses of the tracheae 
to the prothoracic leg were described. To briefly review: 
The ventral trachea 2-a sends a branch to the leg; so 
does a branch of trachea 1-a. Both 1-a and 2-a spring from 
the same branch from the main trunk. The tracheal supply 
of the prothoracic leg, combined as it is with the supply 
to the nervous system, differs from that of the meso- and 
metathoracic legs, but resembles, somewhat the tracheal 
supply of the abdominal prolegs. 
The mesothoracic leg receives its tracheae from three 
sources. First a large branch from near the prothoracic 
spiracle runs backward. This sends a branch to the pos- 
terior apex of the diamond. Behind this branch, the trachea 
divides into a Y, the inner arm of which runs on the outer 
surface of the muscle layer toward the middle of the body, 
and forms the anterior stem of the leg tracheae. The outer 
arm of the Y runs backward and joins, in the wing-bud, 
with a forward running branch of the next large outer 
branch of the main trachea. This large branch springs 
