9 
= 
The upper surface is smooth and convex and carries certain hairs, 
which are usually six in number. Anteriorly the head forms a rather prominent 
rounded mass (the clypeus). In some cases the clypeus carries small hairs 
(clypeal hairs) as in Anopheles and Stegomyia. As a rule it carries only two thorn- 
like spines. When present, the clypeal hairs are of specific importance. 
The clypeus, instead of projecting, may be concave and form a cup-like hollow 
(cannibal larvz). In old larva of certain species a sharp beak-like process cov- 
ered with hairs or spines may project from below the clypeus. At the side ofthe 
head are the large compound eyes, and immediately behind these are the ocelli of 
the simple eyes. 
The lower surface of the head is smooth and convex and is marked by two 
grooves which pass from the outer angles of the mental plate backwards. About 
the middle of the lower surface of the head is a small, dark triangular plate—the 
mental plate or lower lip (Meinert). The mental plate forms a hard and sharp 
lower lip to the mouth. The upper lip is formed by the prominence already 
mentioned (clypeus). Arising on each side of the under surface of the clypeus 
are the feeding brushes. These consist, except in cannibal larvz, of numerous fine 
curved hairs arranged so as to look very like a shaving brush. In cannibal species 
these are much modified, each consisting of a series of stout, curved chitinous 
bars, and are used as a clasfing organ for seizing their prey. The mouth is 
closed in beneath by two plate-like structures,—the maxille@, which can be opened 
to expose the buccal cavity, or approximated to almost meet in the middle line. 
Each maxilla carries on its outer edge a stout, more or less conical, maxzllary 
palp. Some variations occur in the maxilla and palps of different genera ; for 
example, both are very small in A/uczdus (PI. Ill, fig. 14). Lying just behind 
the maxillz are two very stout and large plates of chitin—the mandzbles. On the 
inner side of each of these there is a variable number of large, strongly chitinised 
teeth, which meet together, when approximated, in the neighbourhood of the 
mental plate. Each mandibular plate also has, arising from its anterior edge, 
a variable number of long processes which are used in combing the feeding 
brushes and which vary in size and number in different genera. 
On each side of the head, arising from prominences in front of the eyes, are 
the antenne, These vary very considerably in different genera, and have already 
been shown by us to have great significance in the classification of the anophelina. 
Each antenna consists of a basal segment immoveably fixed and more or less 
blended with the head mass, and a loosely jointed distal segment carrying various 
spines, hairs, etc.,—the antenna proper. When fully developed, three distinct 
portions, which, however, form a single unjointed piece, may be distinguished 
in the distal segment, a proximal, a median, and a shorter distal portion, which 
I have called the first, second, and thzrd portion respectively. At the junction 
