30 



THE CLASS OF INSECTS. 



(These lobes will be explained farther on when speaking 

 of their development in the embrjo.) Behind the epicra/- 



niuin is the occiput^ 

 or base of the head. 

 It belongs to the la- 

 bial, or second max- 

 illary segment, and 

 helps to form a com- 

 plete ring, articulat- 

 ing with the thorax. 

 It is perforated bj' a 

 foramen to afford a 

 connection between 

 the interior of the 

 head and thorax. It 

 is sometimes, as in 

 many Coleoptera, Or- 

 thoptera, and Hemip- 

 tera, elongated be- 

 ^•s- *2. hind and constricted, 



thus forming a "neck." It will be seen beyond, that the 

 labrum and clypeus are in the embrj'O dcA'eloped from a 

 "tongue-like process whose inferior part eventually becomes 

 the labrum, while superiorly it sends a triangular process (the 

 rudiment of the clj^peus) into the interval between the proce- 

 phalic lobes."* This part {i.e. the clj-^peus and labrum) is the 

 most anterior part of the head, and in the embryo, as in the 

 adult, is normally situated in front of the ocelli, and may be 

 compared with the "anal plate," or eleventh tergite, of the 

 larva, f 



Fig. 42. Side view of the front part of the head, together with the mouth- 

 parts of the Humble-bee (Bombus). «, clypeus covered with hairs; h, labrum; 

 c, the fleshy epiphai-ynx partially concealed by the base of the mandibles (rf); 

 e, laciuia, or blade of the maxillfe, with their two-jointed palpi (/) at the base ; J, the 

 labium to which is appended the ligula {g); below are the labial palpi; h, tlie two 

 basal joints, being greatly enlarged; Ic, the compound eyes. — Original. 



* These lobes are folded back upon the top of the base of the head, and they 



seem to form the tergal portion of the hypothetical, elemental ring, orrings, to which 



they respectively belong, and do not seem to us to be the sternal portion, as sug- 



' gested by Huxley, for they are apparently developed in front of the mouth-openmg, 



and form the roof of the mouth. 



t " Lastly, there are certain parts developed singly in the median line in the Artie- 

 ulata. Of this nature are the frontal spines of Crustacea, their telson,and the stiug 



