136 ZOOLOGY. 



hypopharynx^ on the gronnd that the lig-ula may be superior or inferior, 

 both 23ortions being sometimes present, although imequally developed. If 

 the lips and lignla 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 maxilla^, making six sets of organs corresponding to 

 as many theoretical segments. Brulle, who proposes this theory, does not 

 take the eyes or antennae into accgunt 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 antlia or spiral sucker of a 

 butterfly, and the maxilla? of a coleopter, are modified conditions of the 

 same organs ; and he extended this comparison to the mouth of all the 

 orders. The hausteUum of a fly is composed chiefly of the labium, and the 

 proimiscis of a hemipter of the maxillce 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 \\Qii(\. {cajnit)^ exclusive of the attached organs, is named the cranium', 

 the upper part from the front backwards, is the epicranimn / 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 occiput. The anterior margin is the clyjjeus^ 

 and back of this is the front. The part between the eyes is sometimes 

 named the shiciput ,' and the sides of the head gericB or cheeks. The 

 principal part of the head beneath is the gula. The anterior part of the 

 head is often prolonged into a rostru?n^ as in the Curculionidae. 



The antennce 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 antennie may be shorter than the head, and more 

 than twice the length of the body, and the nuniber of articulations m.ay 

 vary from one to fifty, sixty, or more. Long antennos are made up either 

 of many short articulations or of a few long ones. The antenna? ©ften 

 differ in the sexes of the same species, in length, and in the number and 

 form of the articulations. Among the various forms of antenna may be 

 mentioned the setaceous ; mo7iilifor?n, shaded like a string of beads ; serrate,' 

 2)ecti?iate ,' Jjipectinate, vfith a pectination upon each side ; gemctdate, or 

 bent like an elbow ; clavate / flahellate., ,&c. Some have supposed the 

 antennos to be oi'gans of feeling, others of hearing, and others of a peculiar 

 sense, but their use is not known, and may vary in different orders. 



Eyes. Insects have two kinds of eyes, compound and simple, named 

 respectively eyes and stemmata. Tlie former are situated upon the sides 

 of the head, and are composed of many hexagonal lenses placed in contact, 

 340 



