1929] 
Tracheal System of Pyrausta nubilalis 
339 
Pyrausta nubilalis differs from the tomato worm in that 
the cross trachea in the eighth segment of the abdomen 
is not minute, but is a stout connection. In the prothorax 
the connections are apparently similar, but Peterson shows 
no tracheal connection between the posterior apex of the 
diamond and the main trunk. 
Tracheae from the Prothoracic Spiracle 
The arrangement of the trachese from the prothoracic 
spiracle (Fig. 18), from which the organs of the prothorax 
and head are supplied, is much more complicated than that 
in the regions of the body behind the prothorax. It is easier 
to describe these trachese as from the prothoracic spiracle 
than to attempt to correlate them with the study of the 
tracheal supplies to various systems of organs. 
From the spiracle two large branches extend towards 
the head. One of these I believe, for reasons to be set forth 
later, represents the main longitudinal trachea, or the an- 
terior branch from the spiracle. The other branch forks 
a short distance in front of the spiracle, and its inner branch 
forms the stem of the Y which makes up one side of the 
dorsal transverse trachese to which I have referred as the 
diamond. The outer branch goes forward into the head. 
There it branches, and apparently supplies the great mandi- 
bular muscles lying in the side of the head. One branch 
was traced to the region of the base of the antenna, but I 
w r as unable to follow it into that organ. 
The other large branch going into the head from the 
spiracle branches almost immediately. This first branch 
sends out a small braiich, and three larger branches of 
about equal size. The small branch goes toward the head. 
The branch nearest the head of the other three branches 
passes at once to the outer surface of the muscle layer. It 
runs toward the middle of the body, and sends a branch to 
the prothoracic leg. It continues, and sends a branch up- 
ward to the prothoracic ganglion. Then it meets the cor- 
responding trachea from the opposite side, forming a trans- 
verse connection ventral to the central nervous system. In 
its position and its branching to the ganglion, but not to 
