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Fig. 8 Sagital section through abdominal tip of P. humeralis. GC: glandular cells 
under 10th tergite near anus. A: anus. 
more richly endowed with hypodermal glandular cells, especially in 
the area of the paratergites. 
In staphylinid beetles the first fully developed abdominal seg- 
mental ring (tergite plus sternite) is usually considered to be the 3rd 
abdominal segment (Blackwelder 1936). All Pella species have a well 
developed compound tergal gland between the 6th and 7th tergites 
(Fig. 6) as described by Jordan (1913), Pasteels (1968) and Holl- 
dobler (1970). We have also detected glandular cells located pri- 
marily in the 7th segment, which Pasteels (1968) calls postpleural 
glands. According to Pasteels the glandular channels associated 
with these cells open dorsolaterally through the pleural membrane 
between the 7th and 8th segments. Pasteels could clearly see these 
openings in several species (for example in Gyrophanaena affinis ), 
but not in Pella (Zyras) humeralis. In a series of longitudinal, trans- 
versal and frontal sections, we too were unable to detect the external 
openings of these glandular cells. 
At the anterior edge of the 4th, 5th, 6th and 7th sternites are 
found clusters of glandular cells that open through pores in the 
cuticle (Fig. 7A). They are especially well developed in the 7th 
sternite. Pasteels (1968) assumes that the secretions of these glands 
