THE HEAD CAPSULE. 107 



called the gula, and of a rim surrounding the dorsal and lateral 

 parts of the mouth, termed the epistome. 



The upper lip or labrum is attached to the anterior edge of 

 the epistome, and the lower lip or labium is articulated with 

 the anterior edge of the gula. 



The great compound eyes occupy a larger or smaller area 

 on each side of the epicranium. Three simple eyes are situated 

 near the median line on its dorsal aspect, and a pair of antennae 

 are articulated with it in front of, or above the great eyes. 

 Sometimes the antennae are separated from the epistome by a 

 considerable space, which is properly termed the face. 



Historical ResumS.— Hitherto the head capsules of different 

 orders have not been compared with sufficient care to establish 

 a uniform and satisfactory nomenclature, and entomologists 

 have contented themselves with regional terms, such as 

 cheeks {gcnce), forehead (frons), and vertex, or have borrowed 

 morphological terms, such as clypeus, rostrum, epistome, 

 labrum, and labium, and applied them without due regard to 

 the homologies of the parts designated. For example, the term 

 clypeus, originally applied by Fabricius to the part now called 

 the labrum, has been used indiscriminately for every part of 

 the dorsal or anterior surface of the head by different writers. 



Although numerous attempts have been made to establish 

 a uniform morphological nomenclature, so far as I can judge, 

 the only serious one ever made to differentiate and name the 

 sclerites of the head-capsule is the work of Robineau-Desvoidy 

 [49], and his observations were confined to the head capsule 

 of the ' Myodaires' (Muscida). 



The work of comparative morphologists has been, hitherto, 

 entirely founded on the hypothesis that the dorsal surface 

 of the head consists of the sternal region of several pre-oral 

 somites, and that the antennae, great eyes, ocelli, and even 

 the labrum, like the mandibles, maxillae and labium, are modi- 

 fied ventral appendages homologous with the thoracic limbs. 

 Such views rest upon no secure foundation, and have done 

 much to retard the advance of knowledge ; they originated from 

 the statements of Savigny, and it is only recently that any 



