VIII 



146 THE HUMBLE-BEE 



some species they are liable to great variation, and 

 more confidence is to be put in differences in struc- 

 ture, which are perfectly trustworthy when sufficiently 

 great, although, unfortunately, they are not very 

 numerous nor conspicuous. 



Some of the species differ from one another in 

 the length, in proportion to width of the head, 

 more particularly of the cheeks. In the males 

 important differences are often shown in the length 

 of the antennae, in the comparative lengths of the 

 3rd, 4th, and 5th joints of these, and in the shape 

 of the hind metatarsi. 



Many of the most closely related species differ 

 in the quality of their coat ; thus the hairs may be 

 short or long, equal or unequal in length, dense or 

 thin, fine or coarse, erect or decumbent. In some 

 cases these differences are so slight as to be only 

 noticeable when combined with one another. When 

 the hairs are unequal in length the coat is said to 

 be uneven or shaggy. 



One can always tell to what species or group of 

 species a male belongs by examining through a 

 lens the shape of the forceps and wands of the 

 genital armature. An outline drawing of the arma- 

 ture of each of the British species is given on 

 Plate VI. In comparing specimens with these draw- 

 ings it must be borne in mind that the slightest 

 change in the position of the armature, or of its 

 parts, alters its outline, bringing fresh parts into 

 view and causing parts previously seen to disappear, 

 and also that the markings seen on the upper sur- 



