GENERAL HISTORY OF BEES.

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sccxcs. They constantly differ in the species of a longgtenus ( Andrena, Normada, Halictus). In the male of theg;enus Eucera, they have a remarkable extension, being aslcong as the body, whereas folded back they are rarelysco long, or not longer than the thorax in other males,sipeaking in reference only to our native kinds. Int;he females they are not often longer than the head. Itiss in the males of the genus Halictus that they take thegreatest extension. In the male of the genus Eucera,we also find the remarkable peculiarity of the integu-iment of some of the joints being distinctly of an hexa-gonal structure,—a peculiarity often observable in na-ttural structures. In this case it may refer to the sen-ssiferous function of the organ, and to which I shall havecoccasion to revert when I speak of the senses of ouriinsects. We sometimes find the joints of the antennaelmoniliform, something like a string of beads, or withceach separate joint forming a curve, or with their ter-iminal one, as in Megachile, greatly compressed.

The relative lengths of the joints often yield conclusive(separative specific characters, and which may be very(advantageously made available, especially where other■distinctive differences are obscure, and in cases wherethe practised eye observes a distinction of habit, evi-dently specific, although it is difficult to seize tangiblecharacteristics.

The trophi are the organs of the mouth of the beecollectively. When complete in all the parts, as exem-plified in the genus Anthoptera, they consist of the labrwn,or upper lip; the epipharynx, or valve, falling over andclosing the aperture of the gullet; th epharynx, or gullet,which forms the true mouth and entrance to the oeso-phagus ; the hypopharynx which lies immediately below