. The Cambridge natural history. Zoology. 14 IIYMENOPTERA submentum is articulated with the mentum in such a manner that the two can either be placed in planes at a right angle to one another, or can be brought into one continuous plane, and by this 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 IIYMENOPTERA submentum is articulated with the mentum in such a manner that the two can either be placed in planes at a right angle to one another, or can be brought into one continuous plane, and by this 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 two sides of the lorum, but in -Xylo- cojKC, where -the submentum is unusually short, this part reposes. Fig. 7.âSide view of basal portions of proboscis of Bomhus. a, Epipharyngeal sclerites ; 6, arrow indicating the position of the entrance to pharynx, which is concealed by the epiplrarynx, c : d, hypopharyngeal sclerites ; t', vacant spaie between the scales of tile maxillae through which tiie nectar comes : /, lobe ; /', stipes ; r/, cardo of maxilla : h, encephalic pillar on wliich the cardo swings ; z, angle of junction of lores and submentum lorum ; ^â , 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 the 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 outward thrust, and so separate the maxillae from the labium. In addition to these parts there are also four elongate, slender sclerites that are only brought i
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
