POSITION AND TERMINOLOGY OF THE CULICID^ 11 



the under lip the palpi are most perceptible, and must 

 be noticed in the description of species. The remaining 

 oral parts are generally rather small and stunted, having 

 the form of bristles or horny lancets. They are considered 

 as being the tongue {lingua), under jaws {inaxillce), upper 

 jaws {inandihulce) , and upper lip {labrum), the latter shut- 

 ting the under lip from above, and certain prolongations of 

 the chitinous pharynx such as an epi- or hypopharynx. 

 These parts are not particularly valuable in the distinction 

 of species. 



As in other insects, the thorax of Diptera consists of 

 three segments, the prothorax, the mesothorax, and the 

 metathorax ; but in this Order the mesothorax is so much 

 more developed than the other segments, that it forms by 

 far the largest part of the thorax, and in the description of 

 Diptera is exclusively designated by that name, while other 

 names are given to the pro- and metathorax when some 

 particular part of them has to be characterised. The pro- 

 thorax, being generally very little developed, sometimes 

 forms a neck-like prolongation which bears the head, and 

 is then called the neck {collum). Sometimes the fore- 

 corners of the mesothorax or shoulders {humeri) are covered 

 by a lobe of the prothorax {lohulus prothoracis htwieralis), 

 distinctly separated from the mesothorax ; but it is not 

 uncommon for this to be soldered to the mesothorax so 

 that no distinct limit is perceptible, except by differences of 

 colour and armature, in which case it is called the shoulder 

 callosity {callus humeralis). Sometimes also the prothorax 

 is closely applied to the anterior border of the mesothorax. 

 and has then the name of the collar {collare). The meso- 

 thorax frequently also has a transverse furrow {sutura 

 transversalis) crossing the middle of its upper side, and 

 ending on each side a little before the base of the wing ; 

 its presence or absence, as well as its form, furnishes 

 characters of importance in classification. On each side 

 of the pleura or " breast-side " there is, beneath the 

 shoulder, a spiracle belonging to the prothorax {stigma 

 prothoracis). To the back of the mesothorax applies the 

 scutcheon {scutellum), separated from it by a furrow. 



