No. 429.] THE MOUTH PARTS OF INSECTS. 687 
and a usually elongate parallel-sided stipes (s¢.) bearing at its 
terminal extremity the much-reduced three-segmented palpus 
(mx.p.) and a stil smaller two-segmented terminal lobe, or 
galea (ga.), the lacinia being wholly 
wanting; the labium (/Z) has the 
glossze (g/.) (inner terminal lobes) 
fused but emarginate, the para- 
glossze (outer terminal lobes) want- 
ing, and the palpi (Zf.) three- 
segmented and well developed. The 
mouth parts are similar in both 
sexes. 
When the larval dobson is ready 
to pupate (at the probable age of 
three years) it leaves the stream it ' 
has lived in, crawls under some 
stone near the water's edge, and 
changes into a quiet, non-feeding 
pupa, which, however, is not enclosed 
in a hard, opaque cuticle, but retains 
the power of violent wriggling, and 
bears the wing pads and legs only 
loosely appressed to the body. The 
mouth parts of the pupa (Fig. 2) 
show slight yet obvious differences 
from those of the larva (and also 
from those of the imago) The 
mandibles (md.) show a difference 
from the larval mandibles in the 
Character of the dentation and in 
outline of the whole sclerite ; the 
maxilla have short, five-segmented 

; 5 Fic. 3. — Dorsal aspect of head of old 
palpi and two short terminal lobes, larva of Corydalis cornuta, with body 
r Li . di d 
1.€., both galea Cee) tnd aome (E) fere o nce De o e 
and the labium (/.) has its free Z4., larval head wall; Zmd., larval 
margin more emarginate and less larval Utam: lant., larval antenna 
truncate or blunt, the palpi (/i.p.) 4. wall of pupal head ; f.#d., pupal 
iaining three-segmented. pupal bbinn: p-ant., pupal antenna 

