DIPTERA : STRUCTURE. 413 



organs would therefore be useless ; whereas a series of acute 

 instruments for puncturing and penetrating deeper and 

 deeper into the food, and a fleshy canal, up which, by suc- 

 tion, fluids easily pass, is what would exactly be looked 

 for in the workmanship of an omniscient and all-providing 

 Artificer. 



In other groups of Dipterous insects, and more especially 

 in those which prey upon their companions (Asilidte, Em- 

 pidtE, &c.), we find diminished forces in the organization of 

 the mouth : the lancet-like mandibles have vanished, but all 

 the remaining organs appear in full developement. In the 

 Syrphidce the maxillae become smaller, and in Musca they 



A, Msuth of TabanusB, of Musca. 



are completely lost. In the CEstridce the entire mouth is 

 sometimes completely obliterated. The legs are generally 

 long and slender : some instances occur where they are dis- 

 proportionately long, whilst in others they are more or less 

 thickened and spined. The wings agree in their veining with 

 the anterior pair of the Hymenoptera rather than with those 

 of the Neuroptera, only there are fewer transverse nerves. 

 In one group, however (Nemestrina), the wing is reticulated 

 nearly as much as in the Neuroptera. In comparing the 

 upper wing of a bee with the wing of a fly, no particular 

 resemblance is to be traced between the direction and posi- 

 tion of the veins ; but if both the front and hind wings of 



N N3 



