BRITISH HYMENOPTERA. 277 



the northern parts of the country are assiduously searched, no doubt many 

 more will be added. These bees are all burrowers in the grouud, some species 

 prefering banks of light earth, others hard-trodden pathways, etc.; their 

 burrows differ in depth, but are seldom less than about six, whilst others 

 excavate to nine or ten inches; at the bottom of each burrow is formed a 

 small oval cell, or chamber, in which the industrious female lays up a small 

 pellet of pollen mixed with honey; these little balls are usually about the 

 size of a garden pea, varying somewhat in size in different species. Some- 

 times, apparently to economise time, the bee constructs branch tunnels, each 

 having a similar chamber at its extremity; this peculiarity I have observed 

 in A. rubricata and A. fulvescens ; it is also probably not unusual with many 

 other species: when she has completed her task, she closes the mouth of the 

 tunnel. 



These bees are subject to the attacks of parasites: the first to be remarked 

 upon are those bees which compose the genus Nomada; they are more 

 popularly known as wasp-bees, since they bear a considerable resemblance to 

 some of the small solitary species of that family. These parasites appear to 

 be upon a perfectly friendly footing with the industrious bees, and are permitted, 

 without let or hindrance, to enter their burrows. It has been advanced as 

 a proof of the ingenuity and artifice necessary to be employed in effecting 

 the deposit of their eggs in the working bees' nests, that the parasites should 

 bear a close resemblance to the bees upon which they are parasitic: some 

 instances may undoubtedly be advanced, as Apathus and Bombus, and also in 

 the different species of Yolucella which infest the nests of humble bees, but 

 amongst the solitary bees no such resemblance is required to aid in any 

 necessary deception. It may be remarked, that the two cases ai*e not analogous : 

 this is true; and I am not prepared to say that in the case of the Bombi 

 and their enemies, it may not be necessary, but as regards solitary bees it 

 certainly is not; — colonies of Andrenidce and their parasites mingle together 

 in perfect harmony, issuing from and entering into the burrows indiscriminately. 

 I have on several occasions watched with much enjoyment a large colony of 

 Eucera longicomis, the males occasionally darting forwards with great velocity, 

 then turning sharply round, and as it were swimming in circles close to the 

 ground, then darting off again and again in an unceasing round of sportive 

 enjoyment; their industrious partners, whose whole existence appears to be 

 bound up in one unceasing round of labour, would occasionally return home 

 laden with food for their young progeny. Sometimes it would happen that 

 a Nomada had previously entered her nest; when such proved to be the case, 

 she would issue from it, and flying off to a short distance, wait patiently 

 until the parasite came forth, when she would re-enter and deposit her 

 burden. It will be observed, in this instance, that between JEucera and 

 Nomada no resemblance exists in general appearance, one being several 

 times larger than the other, and covered with pubescence of a sombre colour; 

 whereas the parasite is a gaily-coloured insect, destitute of pubescence, and 

 readily observed from the brightness of its colouring. To some extent I have 

 observed that a constant connexion between certain species exists, and I have 

 never met with some species of these parasites except in connexion with 

 VOL. VIII. 2 o 



