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Psyche 
[December 
cross tracheal connection dorsal to the nervous system and 
ventral to the alimentary tract (Fig. 15). 
Trachea 4 lies in the metathorax. It is on the outside 
surface of the muscle layer and crosses just in front of 
the metathoracic ganglion. It is similar to trachea 2. 
The system of numbering is now evident. Beginning 
with the first trachea behind the prothoracic spiracle lying 
on the inside of the muscle layer, extending toward the mid- 
ventral line of the body, which trachea I have called 1, the 
tracheae in each segment behind this that lie on the inner 
surface of the muscles at about the line between the seg- 
ments have uneven numbers. Those transverse tracheae 
lying in the segment and on the outer surface of the muscle 
layer have even numbers. 
Trachea 5 is not a transverse trachea; and the tracheae 
in the abdomen analogous to tracheae 1, 3 and 5, are not 
transverse tracheae. 
Trachea 6 lies in the first abdominal segment. From 
its position on the outside of the muscles and from the dis- 
tribution of its branches, which will be discussed later, it is 
analogous, if not homologous to the other tracheae of like 
position (those with even numbers). But unlike tracheae 
2 and 4, and unlike the corresponding tracheae in the ab- 
dominal segments, trachea 6 is not, as a rule, a transverse 
trachea. In one specimen I found a connection with the 
corresponding trachea from the opposite side. I doubt if 
that was typical. But it must be considered in connection 
with the transverse tracheae because of its position. (Figs. 
16, 17). 
Behind the first abdominal segment there is a transverse 
tracheal connection in each spiracle bearing segment. From 
the second to the seventh segments inclusive, this trans- 
verse trachea is analogous to tracheae 2 and 4, except that 
they lie behind, rather in front of, the ganglia. 
In the eighth segment there is a stout connection between 
the spiracles lying above the alimentary tract. 
Peterson (1912) in speaking of the tomato worm says: 
“In the case of the eighth abdominal segment, only one 
minute dorsal cross trachea was found, while in the pro- 
thoracic region two distinct cross tracheae were observed.” 
