
1905. | Anatomy of the Tsetse-fly (Glossina palpalis). 539. 
integument is stretched. If this flexible skin be removed, a cavity is 
exposed lying below the pharynx (fig. 4, Ph.), across which run the nerves 

Fig. 4.—Dissection of Pharynx, Proboscis, Salivary Ducts, etc., ventral view. 
P., proboscis ; m., soft integument cut away behind the bulb of the proboscis; dp m., 
depressor muscle of the proboscis; r. m., retractor muscles; Ph., pharynx; Ph. w., 
chitinous wings of the pharynx ; PA. c., membranous continuation of the ventral wall of 
the pharynx, to which the retractor muscles are attached ; 7. p., nerve to the proboscis ; 
Gs., esophagus ; S. D., salivary duct. 
to the proboscis (7. p.), a pair of retractor muscles uniting anteriorly (7. m.) | 
and the two delicate salivary ducts (S. D.). The last-named remain 
perfectly distinct and separated from one another until they pass dorsally 
to the median muscle formed by the two united refractors. A stained 
preparation, which I have cleared and mounted in Canada balsam, shows 
the two ducts uniting into a single duct above this muscle. In Stomoxys, 
according to Hansen’s description, the two salivary ducts unite into a median 
duct much further back than I have found to be the case in Glossina. 
Hansen, it may be noted in passing, speaks always of the thoracic salivary 
gland,* but in Glossina these glands are not thoracic, and in Stomoxys they 
are partly abdominal. The immensely powerful muscles of flight, filling 
up the thorax, are probably the cause of the glands being shifted back into 
the abdomen. To follow the further course of the salivary duct after it 
enters the proboscis, sections would be required, which I have not made, 
since Hansen has already described the duct as opening on the hypopharynx, 
as in all other insects. 
The sucking stomach is morphologically a ventral diverticulum of the 
distal end of the cesophagus, which is placed in the two anterior segments of 
the abdomen, its connection with the cesophagus being drawn out into a long 
* Austen also states (“ Monograph,” p. 35) that “the salivary gland [of Diptera] 
is always situated in the thorax.” (The italics are Austen’s.) 
