1929] 
Tracheal System of Pyrausta nubilalis 
349 
to do with the circulatory system is a question. But on 
the suggestion of Prof. C. T. Brues that they may aerate 
the blood, I tentatively place them in the group of tracheae 
to the circulatory system. 
Reproductive System 
The gonads are two whitish kidney-shaped bodies lying 
on each side, adjacent to the heart, in the fifth abdominal 
segment. They resemble, somewhat, the adipose tissue in 
which they are imbedded. 
In the fifth abdominal segment the tracheae, which in the 
other abdominal segments supply the dorsal muscles, the 
heart, etc., send two branches to the reproductive organs. 
There is a branch to the muscles, etc., then a branch to 
the gonad, another branch to the muscles, etc., followed 
by another branch to the gonad, and another branch to the 
muscles, etc. It is a fan-like arrangement, with the first, 
third, and fifth branches to the muscles, fat tissue and cir- 
culatory organ, and the second and fourth branches to the 
gonads. 
The tracheae to the gonads divide into several branches, 
just as they reach the organs, and branches are sent to 
various parts of the reproductive organs. (Fig. 33). 
Tracheae of the Muscles 
The muscles lying between the longitudinal tracheae and 
the mid ventral line receive their air from branches from 
the transverse tracheae, and also from those tracheae of 
uneven number that lie adjacent to the origin and insertion 
of the muscles at the edges of the segments. 
The muscles lying between the longitudinal tracheae and 
the heart receive the principal branches of those branches 
that end in the heart. 
Figures 14 and 15 show the distribution of tracheae 2 
and 3 with their branches to the muscles and illustrate 
the muscular supply. 
