AND MOUTH-PARTS OF CHLOROPS T^NIOPUS. 409 
which he has been unable to distinguish them. " Kappa " is also absent, but 
Peterson has only found this sclerite in Tabanus, Tipula, and Bittacomorpha, 
where it lies "embedded in the membrane laterad o£ the ventral ends of the 
theca." 
The Maxillarij Palps {m.p.) are one-jointed and present no peculiarities. 
Epipharynx and Hypopharynx. 
The epipharynx {ep., figs. 1, 6, 7) lies in the groove on the under side of 
the labrum and is in the form of a gutter, semicircular in cross-section and 
opening ventrally. The hypopharynx (Ap.) is a similar but rather more deli- 
cate structure lying in the groove on the dorsal surface of the mediproboscis, 
its opening facing dorsally so that, when epipharynx and hypopharynx are in 
contact, a closed hollow cylinder of chitin is formed. At about the point of 
junction of mediproboscis and distiproboscis the epipharynx and hypopharynx 
unite to form a short closed cylindrical tube, the distipharynx (d.ph.), whose 
proximal end articulates with the distal end of the basipharynx {b.ph.), the 
cavities of the two being continuous. Although it is certain that the short 
distipharynx consists of united epi- and hypopharynx, it has the appearance 
of being formed by the former alone, which is obviously a direct continuation 
of it, whereas the hypopharynx is separated from the distipharynx by a 
narrow membranous area acting as a hinge, and is easily broken off at this 
point. 
Just distal to its junction with the distipharynx the epipharynx has a 
rather deep groove (e.y., fig. 6) on its surface. The hypopharynx apparently 
lies quite freely in the groove on the mediproboscis, from which it is easily 
detached except at its distal end, where the two are united. As the labrum 
is slightly, and the epipharynx considerably, shorter than the hypopharynx, ■ 
there is a short distal region of the latter which cannot be converted into a 
closed groove by the apposition of the labrum or epipharynx. The distal end 
of the h3'popharyngeal groove is, however, deep, and a study of serial 
sections has afforded some evidence of the possibility of the lips of the groove 
being brought together to form a closed channel, such a closure beino- 
probably effected by an increase of turgidity in the mediproboscis due to the 
pumping in of body-fluid when the proboscis is extended for feeding. 
Basiphary'nx. (Figs. 4 & '>, b.ph.) 
The form of the basipharynx is sufficiently well shown in the various 
figures. It is an organ of suction. Muscles arise from the dorsal surface of 
the basiproboscis and are inserted into the dorsal wall of the basipharynx, 
which they raise by their contraction, thus increasing the capacity of the 
pharynx. Posteriorly the basipharynx ends in two blunt cornua {cu.). 
Peterson interprets the basipharynx as consisting of united ejiipharynx and 
hypopharynx. 
LINN. JOUEN. zoology, VOL. XSXV. 30 
