. The Cambridge natural history. Zoology. 14 IIVMENOPTERA submentum is articulated with the mentum in such a manner that the two can either Le placed in planes at a right angle to one another, or can be brought into one continuous plane, and by tbis change of plane the basal part of the tongue can also be thrust forwards. There is considerable variety in the lengths of these parts in different genera, and the lorum varies in shape in accord- ance with the length of the submentum. The lorum is a peculiar piece, and its mechanical adaptations are very remark- able ; usually the base of the subme
. The Cambridge natural history. Zoology. 14 IIVMENOPTERA submentum is articulated with the mentum in such a manner that the two can either Le placed in planes at a right angle to one another, or can be brought into one continuous plane, and by tbis change of plane the basal part of the tongue can also be thrust forwards. There is considerable variety in the lengths of these parts in different genera, and the lorum varies in shape in accord- ance with the length of the submentum. The lorum is a peculiar piece, and its mechanical adaptations are very remark- able ; usually the base of the submentum rests in the angle formed by the junction of the tw^o sides of the lorum, but in A't/Io- copa, where the suljmentum is unusually short, this part reposes. Fig. 7.—Side view of basal portious of proboscis of Bomhus. a. Epipharyngeal sclerites ; b, arrow iiidicatiug the position of the entrance to pharynx, which is concealed by the epipharynx, c ; d, hypo pharyngeal sclerites ; e, vacant space between the scales of the maxillae throxigh which the nectar comes : /, lobe ; /', stipes ; g, cardo of maxilla : h, encephalic pillar on which the cardo swings ; i, angle of junction of lores and submentum lorum ; k, mentum ; I, base of labial palp ; m, maxillary palp. in a groove on the back of the lorum, this latter having a very broad truncated apex instead of an angular one; in tlie condition of repose the apex of the lorum rests in a notch on the middle of the back of the oral groove, and in some of the forms with elon- gate submentum, this depression is transformed into a deep hole, or even a sort of tunnel, so as to permit the complete stowing away of the base of the tongue, which would otherwise be pre- vented by the long submentum ; another function of the lorum appears to be that, as it extends, its arms have an outw^ard thrust, and so separate the maxillae from the labium. In addition to these parts there are also four elongate, slender sclerites that are only brouglit in
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Keywords: ., bookauthorsh, bookcentury1800, bookdecade1890, booksubjectzoology
