206 Life History of Wirewonns 



trichus placidus, Gyll., a Carabid, by Kemner(8). From the base of this 

 process the chitin is continued in a fairly thick band on the palate of the 

 mouth. 



On either side of the nasale the anterior margin of the cephalic plate 

 bears a tuft of fine yellow hairs, screening the opening of the mouth. 

 The aperture itself is small and of a contracted oval shape. Within the 

 mouth, on its lower surface, the hijpopharynx is situated (Text-fig. 2 d). 

 It is composed of a basal bar of stronger chitin, followed by an anterior 

 portion, less strongly chitinised. This latter is yellow and almost quadrate 

 in form, save for the anterior margin, which is deeply excavated in a 

 semicircular form, leaving a shghtly projecting horn at the entrance to 

 the mouth on either side. Its surface, both dorsal and ventral, is covered 

 with minute hairs in transverse rows. The main portion of the hypo- 

 pharynx is strengthened by a rim of thicker chitin supporting its lateral 

 margins. Its anterior margin and sides, but especially the apices of the 

 projecting horns, bear a mass of fine yellow hairs, which doubtless per- 

 form the same function as do those constituting the penicillus of the 

 mandible and the tufts on either side of the nasale. The apices of the 

 horns fit up to the basal portion of the laciniae on either side, the base 

 of the hypopharynx being slightly anterior to the base of the mandibles, 

 but considerably posterior to the nasale. The length of the hypopharynx 

 in a full-grown larva, measured from the exuvia, was -28 mm., the width 

 •26 mm.^ 



Ventral to the hypopharynx but attached to it at the base is a semi- 

 membranous plate, the floor of the mouth. In length it is about double 

 that of the basal plate of the hypopharynx and therefore is considerably 

 less than the hypopharynx itself. In breadth it extends considerably 

 beyond the margins of the hypopharynx and near its antero-lateral 

 margin bears a small tuft of bristles on either side in juxtaposition to 

 those of the anterior margin of the cephalic plate just referred to. The 

 anterior margin is somewhat bowed inwards and is bordered by minute 

 hairs. VentraUy and almost on a level with the side margins of the hypo- 

 pharynx on either side is a brownish semicircular mark, with five or six 

 alveoli, which may be sensoria, situated in two rows on its anterior 

 border. 



1 Miss A. M. Evans in a recent paper on the hypopharynx and maxillulae (Journ. Linn. 

 Soc. 34 (1921), 429-456) figures the hypopharynx of the larva of Campylus linearis as 

 representative of Elaterid larvae. She considers the anterior portions which I have called 

 "horns of the hypopharynx" to be vestigial maxillulae. In the absence of more evidence 

 than is at present available, I have some doubt in accepting this homology and therefore 

 retain the term used above. 



