28 



JMr. D, F. Cuniminors on the Elead and 



Mouth-parts. — Tiie mouth-paits are merely an extreme 

 development of tlie type shown in Phryganea. In the Hydro- 

 psychidte and Rliyacophilidae and more generalized families 

 of the order the lahrum is short, the mandibles powerful, 

 and well chitinized, and the haustelluin broader than long-, 

 delicate. In Fhrygama and its allies the labrum is elongntt^, 

 the mandibles reduced to small, soft, nipple-like warts, and 

 the haustellum large, long, and fleshy. 



Fio-. 5. 



Head of Tledrotat-ms grarenhorstii (male). Side view, semi- 

 diMgrammatic, greatly enlarged. 



A)it., antenna ; E, eve ; (\ cardo ; *S'. .^tipes ; Lab, labnim ; MP, maxillary 

 palpns ; j\1L, maxillary lolie ; LP, labial palpus ; LI, haustellum. 



In Plectrotarsus (fig^. 4 & 5) the parts consist of: — 



(1) The labrum, which, b( ginning with a short basal area 

 of fairly firm chitin, is produced into a very long, narrow, 

 delicate organ. This, accordii)g to Ulmer,. is generally 

 carried raised above the hypopharynx and slightly curled up 

 at the tip — facts which suggest that it may be used <is a kind 

 of accessory antenna. 



(2) The mandibles (fig. 4 h). 



