332 
Psyche 
[December 
THE TRACHEAL SYSTEM OF THE MATURE LARVA 
OF PYRAUSTA NUB1LALIS HUBN. 1 
By Milton F. Crowell 
The tracheal system of the larva of the European corn- 
borer, Pyrausta nubilalis Hubn. (Lepidoptera ; Pyralididss) 
is of the peripneustic type. There is one pair of functional 
spiracles on the thorax, and eight pairs on the abdomen. 
(Fig. 1). These spiracles open into short stout tracheae 
which lead, on each side, to a large longitudinal trachea 
which runs throughout the length of the body, and from 
which branches go to the various body organs. 
The Spiracles 
The spiracles are of the type described by Kranchner, 
according to Packard (1909), as “bearing lips.” The lips 
are represented by a chitinous ring surrounding the ellip- 
tical opening through the body wall. They are “roof-like,” 
or bent inwards, and are hairy. (Fig. 2). From the spir- 
acle a short stout trachea joins the adjacent longitudinal 
trunk. (Fig. 3). 
The Tracheal Closing Apparatus 
The tracheal closing apparatus (Fig. 3) surrounds the 
short trachea between the spiracle and the main trunk. 
On one side of the trachea, extending about half around 
it, is a chitinous band, the closing how. Attached to one 
end of this bow is one extremity of the closing lever. The 
closing lever runs parallel with a line joining the ends of 
the closing bow, to a point almost halfway between the ends 
of the bow. Here the lever turns abruptly away from the 
