GENERAL HISTORY OF BEES. 
29 
sexes. They constantly differ in the species of a long 
genus ( Andrena, Normada, Halictus). In the male of the 
genus Eucera, they have a remarkable extension, being as 
long as the body, whereas folded back they are rarely 
so long, or not longer than the thorax in other males, 
speaking in reference only to our native kinds. In 
the females they are not often longer than the head. It 
is in the males of the genus Halictus that they take the 
greatest extension. In the male of the genus Eucera, 
we also find the remarkable peculiarity of the integu¬ 
ment of some of the joints being distinctly of an hexa¬ 
gonal structure,—a peculiarity often observable in na¬ 
tural structures. In this case it may refer to the sen- 
siferous function of the organ, and to which I shall have 
occasion to revert when I speak of the senses of our 
insects. We sometimes find the joints of the antennse 
moniliform, something like a string of beads, or with 
each separate joint forming a curve, or with their ter¬ 
minal 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 where 
the practised eye observes a distinction of habit, evi¬ 
dently specific, although it is difficult to seize tangible 
characteristics. 
The trophi are the organs of the mouth of the bee 
collectively. When complete in all the parts, as exem¬ 
plified in the genus Anthoptera, they consist of the labrum, 
or upper lip; the epipharynx, or valve, falling over and 
closing the aperture of the gullet; th e, pharynx, or gullet, 
which forms the true mouth and entrance to the oeso¬ 
phagus; the hypopharynx which lies immediately below 
