W. H. HARRIS ON THE DENTITION OF THE DIPTERA. 395 



Scatophaga. Figure 8, aS'. calida, displays the entiie group of 

 mouth-organs in this insect. The position of the large tooth 

 and the uniform size of the remainder should be contrasted with 

 Figure 9, S. stercoraria, the common dung-fly. The teeth are 

 more unequal in size than those of the first-named species. The 

 large tooth has become the third member of the group, which 

 peculiarity is still further exemplified by Figure 10, S. 

 sci/halaria (?) in which species it occupies a central position. The 

 lateral view is shown in the diagram (No. 2). 



These are interesting examples of slight modifications existing 

 in different species of the same genus. Systematic investigatioi» 

 would probably reveal similar minor variations occurring m 

 other genera. 



Figure 11, Caricea tigrina. The dental organs differ entirely 

 from any of the preceding species. Each lobe contains four 

 cuspidate teeth of unequal size, somewhat triangular, or bayonet- 

 shaped, in transverse section. The basal portions are expanded, 

 and light in colour, indicating their point of attachment; their 

 free ends are dark, dense, and liable to fracture. 



The posterior and anterior parts of the mouth are furnished 

 with four groups of strong setae ; these probably aid the creature 

 in the capture of its prey by entanglement. 



Figure 12, Caenosia sexnotata. This bears a strong family 

 likeness to the last-described species, to which it is probably 

 closely related, but slight modifications occur . which may be 

 briefly referred to. The teeth are more uniform in size, and 

 less triangular in transverse section, the basal portion differs in 

 form, and when a lateral view is obtained it is seen to be 

 deflected at a considerable angle ; the upper portion presents 

 great curvature, and finally the groups of setae are somewhat 

 different in size, shape, and density. A view of the lateral 

 aspect of these teeth is given in the diagram (No. 4). 



Figure 13, Schaenomyza litorella, a maiine species, widely 

 distributed, but rare. The mouth of this insect contains eight 

 powerful, tricuspidate teeth, well shown in the illustration. 

 The anterior and posterior portions of the mouth have groups 

 of setae less dense than in Figure 11. The lateral aspect of the 

 tooth is given in the diagram (No. 3). 



Figure 14, Stomoxys C(dcitra7is. The greatest of domestic 

 pests, a fruitful source of bad language, and an ambassador 



