Mouth-p irts in Plectro tarsus and ^Ethaloj)tera. 23 



mouth-part.", iticluding labium and mandibles, are present in 

 at least one species of ^^^Aa/o/j^^ra, though tiie precise homo- 

 logies of some of the parts are problematical and of great 

 interest. 



K. Lucas (4) gave a very careful account of the mouth- 

 parts of the Limnoj)hilid, Anaholia furcata, IMcLachlan 

 (=^. hevis, Zetterstedt), in which he describes a labium, a 

 pair of first maxillae with palpi and only a single pair of 

 lobes, a large median fleshy haustellum, and a labium with 

 palpi but no lobes. No mandibles were found. Lucas's 

 description holds gooi for the Limnopliilida^, which prove 

 to be tiie only family of Tiiclioptera in which mandibles are 

 absent. Genthe (5), in 1897, demonstrated the presence of 

 mandibles in Hjdropsyche and JSeurichpsis, though he was 

 mistaken in supposing that these two genera possess " kein 

 eigentliches Haustellum." 1 have found the haustellum 

 present in every family of the Trichoptera. It is absent, so 

 far as 1 have discovered, in only one genus — Dipseudopsis — 

 of the family Polycentropidpe. Mandibles exist in all the 

 families as well, if not in every genus (with the exception of 

 the Limnophilidse) ; in some they are large and probably 

 functional, e. g., in Rhyacophila and Hydropsyche. 



In ^thaloptera dispar the head and mouth-parts are as 

 follows : — 



Htad. — This is rather deep, but short fore and aft. The 



Fio-. 1. 



Epicranial area of head of JEtkaloplera disjmr (enlarged). 

 E, eye ; EP, epicranial plate ; MP, median plate. 



two pillars or endosternites of the tentorium, which run 

 across the head from the base of the occipital foramen to 



