136 ZOOLOGY. © 
hypopharynx, on the ground that the ligula may be superior or inferior, — 
both portions being sometimes present, although unequally developed. If 
the lips and ligula be considered to be formed by the union of a right and 
left hand piece, they will correspond to four pairs of organs like the right 
and left mandibles and maxille, making six sets of organs corresponding to 
as many theoretical segments. Brullé, who proposes this theory, does not 
take the eyes or antenne into account in his enumeration. 
The various organs composing the mouth of insects have not the same 
degree of development in all, some being very conspicuous in certain cases, 
and obscure, modified, or obsolete in others. The distinguished Savigny, 
the entomologist who accompanied Bonaparte’s celebrated expedition to— 
Egypt, discovered the remarkable fact that the antiza or spiral sucker of a © 
butterfly, and the maxille of a coleopter, are modified conditions of the ~ 
same organs; and he extended this comparison to the mouth of all the 
orders. The haustellum of a fly is composed chiefly of the labium, and the 
promuscis of a hemipter of the maxille and mandibles. 
Without attempting to divide the head of insects into theoretical seg- 
ments, its various minor parts must be indicated for the purposes of reference 
and description. Its general form is more or less globular, with many 
variations, and it has projections like horns, but they are never articulated. 
The head (caput), exclusive of the attached organs, is named the cranium ; 
the upper part from the front backwards, is the epicranium ; the top of the 
head is the vertex, which is usually the seat of the stemmata or simple eyes; 
and the posterior part is the oceyut. The anterior margin is the clypeus, 
and back of this is the front. The part between the eyes-is sometimes 
named the simciput; and the sides of the head gene or cheeks. The 
principal. part of the head beneath is the gula. The anterior part of the 
head is often prolonged into a rostrum, as in the Curculionide. 
The antenne of insects are situated upon the face near the eyes, by 
which they are sometimes partly surrounded, and they are attached to the 
head by a ball and socket connexion. These organs are generally capable 
of moving at the base, and the various articulations move upon each other. 
The articulations vary much in form and number, and afford good characters 
for classification. ‘The antennz may be shorter than the head, and more 
than twice the length of the body, and the number of articulations may 
vary from one to fifty, sixty, or more. Long antenne are made up either 
of many short articulations or of a few long ones. The antenne often 
differ in the sexes of the same species, in length, and in the number and 
form of the articulations. Among the various forms of antenne may be 
mentioned the setaceous ; moniliform, shaped like a string of beads; serrate ; 
pectinate; bipectinate, with a pectination upon each side ; geniculate, or 
bent like an elbow; clavate; jlabellate, &c. Some have supposed the 
antennee to be organs of feeling, others of hearing, and others of a peculiar 
sense, but their use is not known, and may vary in different orders. 
Eyes. TUnsects have two kinds of eyes, compound and simple, named 
respectively eyes and stemmata. The former are situated upon the sides 
of the head, and are composed of many hexagonal lenses placed in contact, 
340 
