EXTERNAL ANATOMY OF INSECTS. 85 



The blade of the feeler-jaw, in the class Lepidoptera, appears 

 to vary only in length. 



In Diptera, the feeler-jaws are generally of about equal length 

 with the upper lip and mandibles, but are shorter than the lower 

 lip. They are straight, sharp-pointed, and lancet-like. It does 

 not appear that they are generally tubular. The insertion of the 

 feeler-jaws in Diptera presents little worthy of notice. The 

 disk and feeler-bearer are two small pieces, placed above each 

 other ; from the latter proceeds a feeler with from two to five 

 articulations. The blade is the long sharp-pointed part. The 

 helmet is apparently obsolete. The feeler-jaws fluctuate greatly 

 in their development in the various orders and families of 

 Diptera. Curtis, in the work already alluded to, denies 

 their existence in many genera, yet figures the maxillary 

 feelers. This is not reconcilable with the idea of the feelers 

 being secondary parts, or with their name, maxillary. The 

 existence of the hand presupposes the existence of the arm. 

 The existence of the feeler presupposes the existence of the 

 part that bears it. I refer you to the genera Oxycera," Scato- 

 j)haga, Drapetis, Helcoinyza, Sepsis, Tyrophaga, Mede- 

 terus, See. &c. In two of these genera, Scatop/iaga and 

 Helcomyza, I find that the feeler springs from a short and 

 nearly quadrate piece, on which it is not placed quite perpen- 

 dicularly, but leans a little outwards, and to which it is joined 

 by a very evident suture. Is not this smaller basal joint of the 

 feeler the true feeler-jaw? The blade of the feeler-jaws varies 

 little excepting in length. The feelers vary in many particu- 

 lars : the variation in the number of their joints is worthy of 

 notice. In the Culicites they are long and five-jointed, the 

 central joint being the longest. In the Tiptdifes they are 

 short, and have five joints, all the joints being nearly equal in 

 length. In Bibio, and its congeners, nearly the same. In the 

 Tabanites, Asilites, Muscites, &c., they appear to be three- 

 jointed ; the basal joint short and indistinct ; the second more 

 slender, and rather longer ; the third stouter and longer than 

 either. 



In Hymenop>tera we find a considerable change takes 

 place in the feeler-jaws. The bees appear to be the nearest 



" Oxycera. Maxillae and mandibles none. Palpi short, linear, membranous 

 and compressed; thickened, opaque and pubescent at the apex. — Curtis. 



