Central vesicle or vesicula ccntralis. The large bulbous basal portion of the 

 peuis in TIPULID.*. 



Cephalic. Appertaining to the head. 



Chtetotasey, The arrangement of the prominent spines and strong bristles 

 present on various parts of the body in many groups of Diptera. They 

 are very valuable classificutory characters, and are named in accord- 

 ance with the parts of the body on which they are placed, cephalic, 

 thoracic, abdominal, and so on. Those on the sides of the thorax 

 are known as pleural bristles, whilst most of the well-defined and 

 constant ones on other parts of the body have their special names. 

 As, however, none of the NEMATOCEKA possess bristles of chaetotactic 

 magnitude Jt is unnecessary to describe them in full here. They 

 reach their maximum probably both in size and importance in the 

 ASILID^E and MUSCID.E. 



Cheeks, or gena. The sides of the lower part of the head below the eyes 

 and on each side of the mouth. 



Chitine. The substance of which the hard parts of the outer covering of 

 insects is composed. 



Cinereous. A light grey colour, but not so pale as ash-grey. Eidgway * 

 illustrates it as too dark, to my thinking ; his No. 6 " grey " being 

 more my own opinion of the term. 



Claws. See Ungues. 



Clypeus. This is probably present only in those Diptera with highly developed 

 mouth-parts. It is an upper transverse piece, and most obvious in such 

 groups as the TABANIDJE. 



Coarctate.- A term used to designate those pupae of insects in which the future 

 parts are unrecognizable from the exterior surface. 



Cocoon. The outer covering of silk, or similar substance, formed by the larvaa 

 of many insects, in which they pass the pupa state. 



Collare. Osten Sacken's term for the disc-shaped prothorax in many 

 TIFULID.E. 



Collum.The neck. 



Costa. Technically, the entire marginal vein of the wing from base to base, but 

 usually employed in Diptera to denote the anterior margin only from 

 the base to the extreme tip. In some genera this vein, the costal, 

 actually terminates somewhere near the wing-tip, its place then being 

 taken by the ambient vein for the remainder of the marginal distance. 



Costal cell. The cell immediately below the costa or costal vein. See 

 pp. 8 and 13. 



Cotyloid cavity. The opening in the thorax of insects which receives the 

 head of the first joint of the leg, namely, the acetabulum, or if this 

 be absent, the coxa. 



Coxa. The first easily seen joint of the legs, but it is actually attached to 

 the thorax by a very minute joint known as the acetabulum. The 

 coxse are very greatly developed in many groups of Diptera, notably 

 in some of the MYCETOPHILIDJE amongst the NEMATOCEUA,. 



* ' A Nomenclature of Colors for Naturalists ' (Boston, 1886). 



62 



