228 Mr. E. Saunders' Synojjsis oj 



glabrous flattened disk called the "patella"; this in 

 some of the species is very prominent, and projects so 

 as to look like a tooth if viewed sideways. The basal 

 joint of the posterior tarsi is elongate and dilated, and 

 covered with bristly hairs. 



The most important structural characters in the 3 

 seem to be found in the labrum, the clypeus, the antennse, 

 especially in the relative lengths of their 2nd, 3rd, and 

 4th joints, the puncturation, and the form of the 8th or 

 terminal ventral segment ; in the ? the characters seem 

 chiefly to lie in the shape of the face, the puncturation, 

 and the sculpture of the dorsal portion of the 6th seg- 

 ment. 



The colour of the pubescence, &c., also affords good 

 characters, but exposure to the weather greatly alters the 

 general look of the insects, and the colour rapidly fades. 

 The little parasite Styloi)s, so well known to hyme- 

 nopterists, is often the cause of considerable variation in 

 these insects ; its presence may generally be detected by 

 the deformed appearance of the bee's body, or by the 

 actual protrusion of a portion of its own body from 

 between the segments of that of the bee ; it projects 

 something like a small brown seed more or less flattened, 

 and the variations caused by its presence are well worthy 

 of notice. I have to thank Professor Perez, of Bordeaux, 

 for some very interesting remarks on this subject. 



If a <? be stylopised, its general appearance becomes 

 more like that of a $ ; if a ? be stylopised, it becomes 

 more like a S '• thus, in the case of a ^ , its head tends 

 to become smaller, the pubescence of the abdomen to 

 become denser and paler, and to form bands at the apices 

 of the segments, the legs to become more densely hairy, 

 and in the species where the clypeus is white it tends to 

 become black or spotted ; in the case of a ? the head 

 tends to become smaller, as in the $ , the scofiae to 

 become less dense and paler, as also the pubescence of 

 the body, but like as in the 3 it tends to form pale bands 

 at the apices of the segments, and in species where 

 the 3 has the clypeus white, the stylopised ? often has 

 that part white also or spotted with white ; there also 

 seems to be a tendency in both sexes to assume a some- 

 what pallid, immature appearance. The effects of sty- 

 lopisation vary very much in different specimens, some 

 hardly showing any variation from the typical form, 

 others varying to such an extent as to be hardlv 



