52 
Psyche 
[Vol. 87 
empty through the cuticle between the hairs (Fig. 5). A few ducts do 
not run to the brush, but empty through the cuticle lying directly over 
the gland cells (Fig. 4). In both species each mass of gland cells is 
enclosed by a thin basement membrane or lamella (Fig. 6). 
The gland is larger in P. canadensis than in P.fuscatus (Figs. 7 & 8). 
Each cluster of cells contains approximately 1676 cells (2 specimens) 
(56-105 cells per section; 4 specimens) in P. canadensis and 597 cells 
(3 specimens) (18-38 cells per section; 6 specimens) in P.fuscatus. 
The epithelium underlying the class 3 cells is thickened by the 
elongation of the epidermal cells, suggesting that these are secretory 
cells (class 1 cells of Noirot and Quennedey, 1974) (Figs. 4, 7, 8). This 
epithelium is thicker in P. canadensis (x= 34.0 //; 3 specimens) than in 
P.fuscatus (x= 15.5 //, 6 specimens). Epidermal cells not underlying 
the class 3 cells, including those in the hyaline area, are flattened and 
irregular in appearance (unmodified) in both P. canadensis (x= 6.4//; 
3 specimens) and P. fuscatus (x = 5.8 //; 6 specimens). 
5th Sternite. 
The anterior margin of the fifth gaslral sternite of both species 
bears a narrow band of class 3 gland cells, although a brush is lacking. 
Histological sections revealed fewer gland cells in P. canadensis (4-8 
cells per section; 4 specimens) than in P. fuscatus (10-15 cells per 
section; 6 specimens) (Figs. 9 & 10). The gland cells are enclosed by a 
basement lamella. 
As on the sixth sternite, the epithelium lying under the class 3 cells 
is thickened, and is thicker in P. canadensis (x— 39.1 //;■ 3 specimens) 
than in P. fuscatus (x= 7.8 //; 3 specimens) (Figs. 9 & 10). 
There were no detectable individual differences in gland morpho¬ 
logy or development in either species. 
Discussion 
Our most important new finding is that the epidermal cells 
associated with the class 3 gland cells on both sternites are modified 
into what appear to be class 1 gland cells in both species. The reason 
Hermann and Dirks (1974) did not observe this in P. annularis (L.) 
may be attributed to their use of late pupae instead of adults. These 
cells may not become elongated until active. 
A second point on which P.fuscatus and P. canadensis apparently 
differ from what Hermann and Dirks (1974) report for P. annularis is 
that the class 3 cells of sternite 6 clearly form two clusters that lie to 
