Xiv ON THE TERMINOLOGY OF DIPTERA. 



rax 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 the 

 shoulders (humeri) are covered by a lobe of the prothorax (lolus > 

 prothoracis humeralis) , distinctly separated from the mesothorax; 

 but it is not unusual for this lobe to be so soldered to the meso- 

 thorax that it is not possible to discover a distinct limit between 

 them, except in general, by their color or hairs; it is then called the 

 shoulder callosity (callus humeralis). The prothorax sometimes 

 also applies closely to the anterior border of the mesothorax, and 

 has then the name of collar (collare). The mesothorax frequently 

 has a transverae furrow (sutura transversals) 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 important in the classification of Diptera. On each 

 side of the breast the breast side (pleura) there is beneath the 

 shoulder a spiracle (stigma prothoracis) still belonging to the pro- 

 thorax. To the back of the mesothorax applies the scutcheon 

 (scutellum), separated from it by a furrow. Beneath the scutellum 

 a part of the metathorax is to be seen, called metanotum, generally 

 descending obliquely, often very convex, and on each side with a 

 more or less inflated space, called the lateral callosity of the meta- 

 notum (callus metanoti later alis). The poisers (halteres) have their 

 origin beneath this callosity, and before either of them we see the 

 spiracle of the metathorax (stigma metathoracis). The mem- 

 branous covers which in many Diptera are found above this spi- 

 racle, have the name of covering scales (tegulce).* 



The abdomen is the third of the three principal parts of the 

 body, but we usually so call its upper side only, the name of belly 

 (venter) being given to the under side. The segments of the ab- 

 domen are of course, as in the other orders of insects, counted 

 from the front to the back; but the anterior ones are often soldered 

 together, while the posterior ones are stunted, and by their con- 

 cealed situation withdrawn from the eye; much caution is therefore 

 required in counting them. The statements about their number 

 are frequently rather arbitrary and conventional, and often require 

 an explanation. At the end of the abdomen we see in the male 

 the appendages destined to take hold of the female in the copula 



* Some authors call them squamce. 0. S. 



