56 ' [February, 1901. 



Swimage were similarly attached to a lar^e colony, then in full activity 

 of Andrena fulvicrus. I hardly think H. xanthopus could have been 

 their host on this occasion ; certainly not a single specimen of the 

 species was to be seen, and I could scarcely have overlooked so 

 remarkable an insect, had it been there in suflBcient quantities to enter- 

 tain the Sphecodes. 



But more than this, from a long series of observations made by 

 me this spring 1 am strongly inclined to think that even hibernating 

 species of Sphecodes occasionally attach themselves not to HaJictus 

 but to Andrena. There seems no reason why they should not do so ; 

 the food stored by a spring Andrena and a Halictus is derived from 

 the same sources and probably very similar, and supposing a young 

 Sphecodes to be reared in an Andrena' sceW it could chose its own time 

 for emergence, and might appear in the autumn, whether the Andrena 

 had an autumn brood or not. In the particular case in question the 

 Andrena was double-brooded. The case was as follows : — 



A. fulvicrus is very abundant in this neighbourhood, and I have 

 paid repeated visits to large colonies of it — one freshly formed this 

 year in a new sand cutting — in hopes of finding its parasite, Nomada 

 fiicatu, which I have taken abroad in the spring, though in England it 

 seems to be an autumn species only. However, in none of all the 

 colonies I visited could I find a single Nomada, except one specimen 

 (evidently there by accident) of N. fiavoguttata. But I noticed, over 

 and over again, various species of Sphecodes, especially gibbics, sub- 

 quadratus and similis, dodging about the Andrena burrows, and some- 

 times actually entering and remaining in them for some little time. 

 Once or twice I saw a Sphecodes pop into a hole and suddenly pop out 

 again, followed by the Andrena's head and shoulders, the latter dis- 

 appearing again when the intruder was gone. On another occasion, 

 when the owner of the ground was with me looking at this little 

 scene, wp s?-v an Andrena issue from a hole and fly away, and shortly 

 afterwards saw another bee enter the same hole and remain there for 

 a considerable time. Then it came out and we netted it. It was a 

 Sphecodes gibbus $. 



I do not say that all this proves even occasional inquilinism of 

 Sphecodes on Andrena. The visits of the former to the holes of the 

 latter may have had some other reason, but they certainly took place, 

 and were too frequent, I think, to be due to pure accident, as when 

 the other day I saw a Cercerts ornata $ making furious dashes at a 

 hole, out of which presently came a Cerceris arenaria $ , whereupon 

 the ornata went in with an air of possession, and the arenaria flew 



