PSYCHE. 



THE MOUTIIPARTS OF THE NEMATOCEROUS DIPTERxV, V. 



BY VERNON L. KELLOGG, STANFORD UNIVERSITY. 



Resume. 



Having examined the mouth struc- 

 ture of representatives of all (e.xcept 

 one) of the families of Nematocerous 

 Diptera we are in position to state in gen- 

 eral and inclusive terms the characters 

 of the mouthparts of the Nematocera. 



The mouthparts are composed of 

 (retaining the nomenclature hereto- 

 fore used) a labrum-epipharynx, a pair 

 of mandibles, wanting in the males of 

 all families, and wanting in both sexes 

 of a few families, a pair of maxillae, 

 in which never more than one terminal 

 lobe is present, and this failing in a few 

 instances, and a labium, whose palpi 

 are totally lost, and whose terminal 

 lobes show a considerable range in 

 degree of coalescence. The condition 

 of the various parts may be described in 

 more detail as follows : 



The labrum-epipharynx is always 

 present and always free ; it is longer 

 than broad, pointed though not always 

 sharply^ and, as seen from above, well- 

 chitinized. It is composed of two 



lamellae (often separable by dissec- 

 tion, or by treatment with potassium 

 or sodium hydrate) of which the upper 

 or dorsal one is a well chitinized 

 sclerite and is the labrum s. str. The 

 lower or ventral one is a thin membran- 

 ous structure, often projecting slightly 

 beyond the labrum and in almost all 

 cases bearing few or numerous taste 

 pits (?) and papillar sense (?) hairs. 

 The mandibles are, when present, 

 possessed only by the females ; they 

 are wanting in both sexes in six of 

 the eleven families studied. The man- 

 dibles in the five families possessing 

 them are always free and distinct but 

 show very obviously their tendency 

 toward reduction and disappearance. 

 In their best developed and certainly 

 effectively functional condition, they 

 are long, slender, well-chitinized and 

 armed with a fine but conspicuous den- 

 tation along their inner margin. From 

 this condition they descend by quick 

 steps to the condition of small thin 

 weakly-chitinized delicate plates, practi- 

 cally functionless. 



