1980] 
Post & Jeanne — Sternal Glands of Polistes 
57 
likely to be smeared onto the nest petiole during rubbing. On the 
other hand, at least three facts could be interpreted as arguments 
against an identical role: (1) P. fuscatus has more gland cells on the 
5th sternite than does P. canadensis, just the reverse of the condition 
on sternite 6 (although the epidermal cells of this sternite are thicker 
in P. canadensis, suggesting perhaps that they have an independent 
function); (2) The tuft of long hairs present on sternite 6, where it 
presumably acts as an applicator brush, is absent from sternite 5; (3) 
the class 3 gland cells are distributed in a narrow transverse band on 
sternite 5, very unlike the two lateral clusters found on sternite 6. 
Although we detected no significant individual differences in gland 
size or morphology in either species, the ages and castes of our 
specimens were unknown. A careful EM study correlating degree of 
glandular activity with age and caste could provide useful insight into 
the function or functions of these glands. 
Acknowledgments 
B. Jane Harrington provided helpful comments on an earlier draft 
of this manuscript. Martin Garment provided assistance and advice 
on scanning electron microscopy. We thank Donas Erica and Violeta 
Hagmann for their generous hospitality shown us during our stay in 
Brazil. This research was supported in part by the College of 
Agricultural and Life Sciences, University of Wisconsin, Madison, 
and by National Science Foundation Grant BNS-77-04081. 
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