XX 
DESCRIPTION OF PLATES 
Plate XV 
Fig. I. Transverse section of proboscis of the female Anopheles costalis near its tip ( x 460). 
Ir-ep, labrum-epipharynx ; the two portions are shewn separated by a thin red 
transverse band ; /;, hypopharynx, with salivary canal at its centre ; m, mandible ; 
mx, maxilla ; lb, labella ; /, tip of labium ; fh, superior region of inner surface of 
labella from which arises a feltwork of fine hairs; ch, inferior region of inner surface 
from which coarse hairs arise ; r, a ridge of thickened chitin on the middle region of 
the inner surface, which above at its base enters into the articulation of the labella 
and labium. 
Fig. 2. Transverse section of proboscis at the level of the labella joints ( x 460). h'-ep, h, 
m, »w, as in fig. 1 ; ?nx.p, maxillary palp ; /, lateral pear-shaped area at extremity 
of labella ; In, nerve to the labella ; a, chitinous articulating surface of the labium ; 
k, triangular area, occupied by a loose delicate membrane hanging from beneath 
the portion of the upper chitinous surface of the labium, which is prolonged to the 
extreme tip of the proboscis. In the section, the cut edge of the membrane is shewn 
as an irregular line. In this figure the labrum is not represented. 
Fig. 3. Transverse section about the level of the middle of the proboscis ( x 460). Ir-ep, h, m, 
mx, mx.p. as in figs. 1 and 2 ; /, labium ; Ltr, trachea to the labium ; l.n, nerve to the 
labium ; r, lateral chitinous ridge of the labium ; l.m, labellar muscles. In this figure ' 
the labrum is not represented. 
Plate XVI 
Fig. 1. Transverse section at the base of the proboscis of the female Anopheles costalis (x 460). 
/r, labrum ; ep, epipharynx ; ep.r, lateral supporting chitinous ridge of the epipharynx 
containing core of chitin forming cells ; hypopharynx with salivary gutter ; ?n, 
mandible ; ?nx, maxilla ; mx.p, maxillary palp ; 0', a concave region on the inner sur- 
face of the maxillary palp, against which the mandible fits, indicating the relation of 
its origin ; 0", a similar region for the maxilla ; p.m, muscle of the maxillary palp ; 
/, labium, note the shape at this level as compared with sections, plate xv, fig. 3 ; r 
lateral chitinous ridge of labium ; Ltr, labial trachea ; In, labial nerve. 
Fig. 2. Transverse section of proboscis just before the separation of the various mouth parts 
from each other ( x 400). c, clypeus ; f, upper posterior angle of the fulcrum ; 
Ir, proximal extremity of labrum, note the cubical cells ; Ir.p, chitinous prolongation 
of the labium within the clypeus; em, epipharyngeal muscle; ep, epipharynx; 
h, hypopharynx, the apex of the salivary receptacle is seen below, supported by two 
lateral chitinous bars ; m, mandible ; mx, maxilla, note its sickle shape ; mx.p, maxillary 
palp; pn, nerve to maxillary palp; pm, muscle to the maxillary palp; /, labium; 
In, labial nerve ; ltr, labial trachea ; note the line of cleavage of the labium from the 
other mouth parts. 
Plate XVII 
Fig. i. Transverse section of the head of Anopheles costalis, at the level of the middle of the 
ascending portion of the pharynx ( x 360). p, ascending portion of the pharynx ; 
pd, middle membranous portion of the upper wall of the pharynx, consisting of a 
layer of low cubical epithelium ; pv, lower chitinous plate of the pharynx ; pm, 
pharyngeal muscle; Ibr.m, fan-shaped labral muscle; sd, common salivary duct; 
