154 The Proboscis of the House-fly. [ March, 
Its Structure —The proboscis consists of three divisions—base, 
mid segment and tip. The base, or proximal division, contains : 
1. A large framework of hard dark-colored chitin (fin Fig. 1, 
A and &, represented in 
the margin as spread out). 
This has been termed the 
pharynx, or fulcrum, by 
Lowne.! In the natural 
position this fulcrum is a 
narrow box, open at both 
| ends, and sending pro- 
cesses backwards. and for- 
wards. The distal part of 
its roof is left open so as 
to receive the mid segment 
ae ae Juicrum spread out, showing | : F 
s lower (ventral) plate with curved margins, its in flexion. One of Lowne’s 
fpr Syd + aad sibdistal (4) processes, its wings : : 
D which arch over its ARCEN and meet above, terms for it (2 harynx) 15 
ais peeve processes (¢). It terminates incorrect; it is rather a 
distall in a small node le. : 
: case surrounding the phar- 
-ynx. I shall refer to it by the name fulcrum. 
2. Two palps (/ in Fig. 1, Æ and B) not jointed, but borne on a 
weak cross-piece of chitin. (The blow-fly has stronger supporting 
bars, and palps longer and more slender.) 
3. A transparent funnel-shaped sheath widening towards the 
head, surrounds the basal division. This membrane consists of 
chitin, but is quite soft and movable, like the membrane of the 
trachez or the web of the wings of insects. It is directly contin- 
uous with the walls of the head, and it extends forward to enclose 
the whole proboscis and to form the walls of the lips. It is open 
above so as to allow free motion to some of the hard parts. 
-The mid segment folds on the basal segment by an elbow joint. 
On the under side of the mid segment is the mentum, or chin 
piece (m in Fig. 1 A), truncated behind, narrowing and bifurcated 
in front, not articulated to any hard supporting part, but fixed in 
the membraneous sheath which holds it in its place. 
Uppermost in the mid segment is the operculum of Lowne (0 in in 
Fig. 1 A, Band Fig. 3). This is a semi-tube, slit beneath, pointed in 
front, and sending backwards two long as which I shw 
cali “the great tendons.” , 
1“ The Anatomy and Physiology c of the Blow fy, by pE Lowne, Lond, 1979. ca 
