326 



INTRODUCTION TO ARTHROPODS 



hypopharynx (Fig. 134, Hyp.), a short fleshy organ lying in the 

 midst of the other organs, and comparable in both form and 

 function with the tongue of vertebrate animals. In addition to 

 these parts there is a horny hning of the upper lip and roof of 



Lb 



m. 



Fig. 134. Simple mouthparts of a chewing insect (Steiwpalmatus) ; Ibr., la- 

 brum, or upper lip; mand., mandible; hyp., hypopharynx or tongue; max., maxilla; 

 max. p., maxill.'iry palpus; Ibm., labium or lower lip (really a second pair of maxillaj 

 fused together); lab. p., labial palpus. 



the mouth cavity known as the epipharynx. This structure 

 is usually closely associated with the upper lip, so that the com- 

 bined organ is spoken of as the " labrum-epipharynx." 



The extent of the modifications which these mouthparts may 

 undergo is wonderful, especially in insects where they are modi- 

 fied for sucking or piercing. In the true bugs the mandibles 

 and maxilla3 are prolonged into needle-like organs, the maxillie 

 often armed with sawlike teeth at their tips, and the lower lip 

 is developed into a thick, fleshy, jointed proboscis, grooved on its 

 upper side to form a sheath for the piercing organs (Fig. 164). 

 The labrum is a short movable flap, and the hypopharynx is very 

 slightly developed. In the Diptera, which include the mos- 

 quitoes, gnats, blackflies, tsetse flies and other biting flies as 

 well as hou.seflies and blowflies, there are several different types 



