412 ORDERS OF PTILOTA. 



to perceive that the terminal joints are, with the exception 

 of those composing the seta, so entirely soldered together 

 that their union is not visible. The eyes are lateral, and in 

 many instances those of the males are much larger than in 

 the females, uniting upon the crown of the head. In others 

 they are so large as to occupy nearly the entire head, leaving 

 but a small space only for the mouth. 



In those species which have the mouth more perfectly de- 

 veloped than the rest, and which consist of the blood-thirsty 

 gnat and gad-fly, we find a series of organs, greatly modified 

 of course as to their form, in order to fit them for their 

 functions, but which, as to their number, correspond with 

 those of the mouth of the true mandibulated insects, so that 

 it is equally impossible for us to arrive at any other conclu- 

 sion than that the parts of the mouth of the fly represent, in 

 an altered state of developement, the parts of the mouth of 

 the beetle. We accordingly find that the mouth in Tabanus 

 consists of a large fleshy organ, having a fleshy pair of lobes 

 at its extremity, and which, being the lowest part of the 

 mouth, corresponds with the lower lip of the beetle. At tin- 

 sides of this, and rather higher in the mouth, is attached a 

 pair of lancet-like organs, having a pair of large biarticulate 

 palpi arising from the base: these constitute the maxilla- 

 and the maxillary palpi. Still higher in the mouth another 

 pair of lancets appears, which represent the mandibles, whilst 

 a larger horny piece, channelled beneath for the reception of 

 the others, forms the upper lip (labrum). Within the mouth 

 another very fine lancet appears, analogous to the tongue of 

 the grasshopi>ers, an organ seldom developed to any extent 

 in the Coleoptera. When we consider the habits of these 

 insects, it is evident how necessary it is that the organization 

 of the mouth should be fitted for a different employment from 

 that of masticating. These habits arc essentially suctorial, 

 and the food of the insects is essentially fluid. Hroad horny 



