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 antennae 

 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 A nthoptera, they consist of the labrum, 

 or upper lip ; the epipharynx, or valve, falling over and 

 closing the aperture of the gullet; the pharynx, or gullet, 

 which forms the true mouth and entrance to the oeso- 

 phagus; the hypopharynx which lies immediately below 



