1890.] 233 



is in an early stage. These find the nest that has beeu commenced, 

 and attach themselves to it, managing to keep on fairly friendly terms 

 with the founder until they have eggs to lay, when a duel is generally 

 fought, which results in one or the other being stung to death. The 

 chief benefit to the species resulting from the attachment of several 

 females to one nest would seem to be in preventing the young from 

 perishing should the real mother by any chance get lost. (A similar 

 provision is apparently made in the case of our social wasps). B. 

 ter7^estris is especially liable to this kind of self-parasitism. From one 

 nest I dug up there were found the remains of no less than twenty 

 females under the nest. The hole leading to the nest was short, with 

 a conspicuous entrance. B. lajjidarius is also much given to this 

 habit. 



This tendency on the part of the females of these pollen-storers 

 to join themselves to nests already started somewhat resembles the 

 habits of the Psifhi/rus, and I have noticed an interesting fact in 

 connection with the life-history of B. terrestris which seems to fur- 

 nish a remarkable connecting link between the habits of this species 

 and those of its inquiline Psithyrics vestalis. 



Bomhus fet'restris occurs with us in two races, which were long 

 considered (and are still so by some) as distinct species, viz., lucorum 

 and terrestris. Race lucorum may be roughly distinguished from race 

 terrestris by the pure white, not tawny, hairs on the apex of the fourth 

 and the following dorsal segments of the abdomen, and by its smaller 

 size. It also appears earlier in the spring than terrestris, and lives in 

 somewhat smaller colonies, having milder tempered workers. From 

 observations extending over some years made in the neighbourhood 

 of Dover, I have found that the nests of lucorum are not liable to 

 the attacks of any Psithyrus, but that they are frequently attacked 

 by the queens of its sister race, terrestris, which, on finding the nest 

 in suitable condition will kill the lucorum queen and take possession 

 of the nest, getting the young lucorum workers to raise its young in 

 the same way that Psithyrus vestalis attacks nests of B. terrestris ; 

 and I believe that in some cases such terrestris queens scarcely con- 

 tribute a grain of pollen to the food of their young. It is clear that 

 the pollen brush on the posterior tibiae of such fe7-restris females is 

 almost useless to them, and they might almost as well be devoid of it 

 altogether, as is the Psithyrus, and become to all purposes a Psithyrus. 

 It is remarkable that the old terrestris queens become bald in the nest 

 more quickly than other Bomhi, just as do the Psithyri. 



"With these facts it would not require a very ingenious evolu- 



