16 MOUTH OF GNATS AND FLIES. 



the sheath ; the fifth represents the tongue ; it is con- 

 sidered to be the principal agent in wounding the 

 victims of these little blood-suckers. Over all these 

 is another piece broader than the rest, this is the 

 labrum. This complexity of structure, however, is by 

 no means universal in those insects whose lower lip 

 exhibits the formation above described; in some of 

 them the bristles or lancets are reduced to an exceed- 

 ingly small size, or altogether wanting ; in others, a 

 single piercer, the tongue, is present, whilst in others 

 the bristles representing the maxillae and mandibles 

 make their appearance together or separately. When 

 the maxillary bristles are deficient, the maxillary 

 palpi are usually found attached to the stalk of the 

 labium. 



We have thus disposed of four out of the five 

 examples of suctorial insects to which reference has 

 been made ; the fifth is an insect whose very name is 

 a terror to all good housekeepers. But the common 

 Bug has only been selected as a familiar example of a 

 peculiar structure ; the numerous other insects which 

 partake more or less of its characters, although often 

 distinguished by the same unsavoury qualities which 

 render our domestic species such a very disgusting 

 neighbour, are at all events free from its most dis- 

 agreeable associations, they inhabit the fields and 

 woods, and are often of great beauty, a quality for 

 which the common Bug is certainly not remarkable. 

 In these insects we find a horny beak (rostrum, or 

 promuscis] of variable length, springing from the 

 under side of the head, and lying folded down beneath 

 the body when in repose. This, on examination, is 

 found to be a tube composed of three or four joints, 

 and open all along its anterior surface; it is evidently 



