BRITISH HTMENOPTERA. ANTHOPHILA. 413 



widened towards the apex, it is sometimes quite short and 

 triangular, at others many times longer than wide. It also 

 varies in substance, in some genera being clear and hyaline, 

 in others dark and opaque ; it is short and more or less hyaline 

 in the early genera of the short-tongued bees, and elongate 

 in most of the true Apidse, and in the somewhat aberrant short- 

 tongued genera, such as Macropis, Cilissa, and Dasypoda ; 

 whereas in Panurgus again the short hyaline form shows itself, 

 and in Bombiis, Psitliyrics, and Apis, although not hyaline, it 

 is short and triangular. Beyond the submentum comes the 

 mentum itself, which is brown, chitinous, and semitubular, and 

 forms a supporting sheath for some of the softer parts of 

 tlie apparatus to lie in ; above, it is sometimes strengthened 

 by elongate sclerites, as in Megacliile, Osmia, &c. ; it varies 

 very little in form, being usually slightly narrowed and rounded 

 at the base, truncate or produced into one or more lobes at 

 the apex beneath ; from either side of the apex extends one 

 of the labial palpi, and from between them the so-calJed lingua. 

 Near the base of the mentum on each side is attached a sclerite, 

 which passes upwards between the maxillae and thence under the 

 labrum, where it is abruptly angulated, its apex lying just at the 

 side of the anterior edge of the oral groove, close to the emargi- 

 nation into which the cardo articulates. These sclerites hold the 

 upper part of the membranous bag expanded anteriorly when 

 the tongue is extended. Huxley has called them " the sclerites 

 of the hypopharynx." They are united to the maxillae by the 

 investing membrane, which just at the point of union on either 

 side gives rise to a sort of scale which is often fringed with 

 bristle-like hairs ; these scales, which appear to exist in all our 

 genera, although obsolete in Apis, seem to have been scarcely 

 noticed by authors ; they are very much developed iu Anthopliora 

 and also in Megachile, Osmia, and their allies. Beyond the basal 

 ends of these sclerites, and with their anterior extremities lying 

 between them, are two others, which can only be seen when the 

 elypeus and face and the top of the oesophagus are removed ; 

 they are what Huxley has called the " sclerites in the wall of the 

 oesophagus." They converge posteriorly, and are somewhat 

 hamate at their posterior ends ; the membrane which lies between 

 these forms the floor of the mouth. Anteriorly, this membrane 

 is chitinized, and forms what has been called thehypopharyngeal 

 plate ; on this chitinized portion, which is slightly concave, may be 



LINN. JOUEN. — ZOOLOGY, VOL. XXIII. 29 



