272 LMiiy, 



All round Oxford the stone walls are often covered on the top 

 with mud scraped from the road side. In the mud on one of these a 

 colony of H. rubictmdus, Christ, was established, occupying a length 

 of a yard or so ; in this small space, however, were crowded hundreds 

 of burrows, and amongst the scores of the Halictus that were entering 

 these, laden with pollen, now and then a specimen or two of S. gibhus 

 would be seen hovering around, or going in amongst them. And yet 

 there were dozens of yards of wall, with mud exactly similar, equally 

 ill the sunshine, and quite unoccupied. 



This same species {S. c/ihhus) was chief actor in a scene far more 

 interesting. On the 9th of last June, on a hard sandy pathway, I saw 

 a female, as it seemed at first sight, digging a burrow. Soon, however, 

 it appeared to me to be enlarging the opening of one already formed. 

 Its head was hidden in this opening, and with its head in this position 

 it would now and then turn slowly round in a circle. I may here say 

 that I had placed my net over it, and was watching it through this, but 

 it took no notice — probably it was too much occupied otherwise. 

 Presently it retreated backwards an inch from the opening, when, to 

 my surprise, I saw another bee a short way down the burrow. This 

 afterwards proved to be a worn ? of H. leucozonius. The Sphecodes 

 now made a rush down the burrow, and set to work attacking the tail 

 of the Halictus with its mandibles. Again the former left the burrow, 

 and was this time followed by the other. But now finding themselves 

 prisoners, their only thought was of escape, so I was unable to see 

 what would have been the end of the struggle. 



As to the flowers which these females visit, I have only seen them 

 myself once or twice on the common daisy, and once on the blossom 

 of the whitethorn, but from their love of settling on other white 

 objects (as mentioned above) I am inclined to think that in these 

 instances it was only for the purpose of sunning themselves. 



Several of the facts I have mentioned would seem to point to the 

 genus being parasitic on Halictus, but the weight of evidence seems 

 in favour of its being non-parasitic. It is difficult to see how the 

 point can be proved, except by rearing them from the burrow, though, 

 possibly, it may have been settled by some Continental Hjmenopterist. 



As to battles between host and parasite, Shuckard mentions 

 them between Anthophora and Melecta, and Colletes and Epeolus ; 

 these I have had no chance of seeing, but what is more curious, I have 

 seen two females of the Fossor, Agenia variegata, Linn., fight with the 

 utmost fury, the one having entered the other's burrow. 



