THOMPSON: ANATOMY OF MOSQUITO. 
155 
complicated type of Dipteran alimentary canal that he studied, refers 
to the pump as “ oesophageal bulb ” and to the subclypeal canal as 
“pharynx.” On the other hand, Nuttall and Shipley (:01-:03) in 
their careful study of Anopheles term the subclypeal canal “buccal 
cavity” and the pump “pharynx.” The older of these nomenclatures 
has decided advantages over the newer system used by Nuttall and 
Shipley in that it recognizes the probable equivalence between the 
pump and the anterior end of the “ esophagus ” of such a fly as 
Musca, and in that it gives the expression pharynx — which is gen¬ 
erally employed in insect morphology to indicate the first differen¬ 
tiated intracephalic region of the stomodaeum — to the constantly 
present subclypeal canal rather than to the inconstant pump. It also 
leaves the term buccal cavity vacant and available for any subregion 
of the subclypeal canal which it may seem best to delimit. 
A study of the larvae of the Diptera in the above connection 
offers no assistance, but rather complicates the problem. A major¬ 
ity of Dipterous larvae have a fore gut that is practically undiffer¬ 
entiated throughout its cephalic extent. In other forms, well 
marked regions are present. But these are not always comparable, 
even in closely allied genera, e. c/., Culex and Corethra. Further, 
the larval regions may or may not coincide with the regions of the 
imaginal tract. The wriggler of Culex has a buccal cavity and a 
pharynx, the latter being imperfectly distinguished from the esoph¬ 
agus below and at the sides. But the larval buccal cavity and 
pharynx both go to form the subclypeal canal of the imago and the 
pump of the latter stage is derived from the anterior end of the 
esophagus of the larva. Such peculiarities find their explanation in 
the extremely adaptive character of the Dipterous larva, but this in 
turn makes it unwise to lay stress on larval relations, in an attempt 
to obtain a system of names for the imaginal parts. 
Employing the nomenclature just chosen, the stomodaeal portion 
of the alimentary canal of the mosquito shows successively: the 
labral or proboscis canal, the subclypeal tube or pharynx, the pump 
or antlia, and an esophagus which extends through the occipital 
foramen into the thorax. The midgut is differentiated into cardia 
and stomach or mid-intestine. The hind gut is modified to form an 
ileo-colon and a rectum. Valves are developed at the union of 
pharynx and antlia, pharyngeo-esopliageal valve, at the posterior 
end of the antlia, at the junction of esophagus and cardia, eso- 
