342 Psyche [December 
sends small branches to the metathoracic and first abdom- 
inal ganglia. (Fig. 19). 
The metathoracic ganglion receives, in addition to the 
small branches from trachea 5, branches from trachea 4. 
These run backward, one on each side, to the ganglion. 
(See Fig. 14, representing trachea 2). 
The first abdominal ganglion receives, on each side, a 
small branch running forward from trachea 6, as well as 
branches from trachea 5. (Figs. 16 and 17). 
The abdominal ganglia receive their air supply from the 
transverse tracheae. In the abdomen these all are found 
on the outside surface of the muscle layer. The tracheae 
corresponding to tracheae 1, 3, and 5, do not enter the ner- 
vous system. Another difference is that in the thorax the 
transverse tracheae of even number, 2 and 4, lie in front of 
the ganglia and send their branches backward to them, 
while in the abdomen the transverse tracheae lie behind the 
ganglia, and the branches to the ganglia run forward. The 
tracheae that form the transverse tracheae in the abdomen 
divide into an anterior and posterior branch. It is the 
posterior branch that meets the corresponding trachea from 
the other side, forming the transverse connection, and from 
this branch, also, that the branch divides that supplies the 
ganglion. The anterior branch may send branches to the 
ganglion, but apparently more often it does not. (Fig. 20) . 
The seventh and eighth abdomnial ganglia have coalesced 
and lie in the seventh abdominal segment. The trachea that 
normally would supply the seventh ganglion here supplies 
both. There is no separate connection between the eighth 
ganglion and the tracheal system. (Fig. 21). 
Peterson (1912) figures two transverse tracheae in the 
tomato-worm larva sending branches to these ganglia, the 
one supplying the seventh passing under the eighth, and 
the trachea sending branches to the eighth is apparently 
the transverse trachea between the spiracles of the eighth 
abdomnial segment. Careful search failed to discover any 
trachea from this transverse trachea to the nervous sys- 
tem in Pyrausta nubilalis. 
The commissures between the ganglia are usually sup- 
plied by branches from the transverse tracheae. In the ab- 
