306 BRITISH BEES. 



at the upper part of Hampstead Heath, to Highgate, from 

 which road it was separated by merely a band of whins 

 and coarse grass, used to be a very favourite collecting 

 place of mine, for there, and in its immediate vicinity, 

 I have often caught, within a very brief period, more 

 than half the genera, and a very large number of the 

 species of the fossorial Hymenoptera. One particular 

 little spot was inhabited by Psen equestris, rare every- 

 where else, and our largest Cerceris, who carried on their 

 instinctive pursuits during all the summer months, but 

 at a particular time in the autumn, varying slightly 

 with the nature of the season, a flock of wagtails (Mota- 

 cilla) would alight and make brief work of those fossores 

 which were still aflight ; and this was repeated season 

 after season, as if the wagtails thought it was time that 

 their own rapacity should stop the course of these pre- 

 dacious insects. But to return, the female Apathi then 

 resort to the nests of the Bombi whence they have issued, 

 and lay themselves up in their winter dormitory. That 

 this must take place speedily after impregnation is ren- 

 dered almost conclusive by the fine state in which their 

 pubescence appears in the spring, which would be tar- 

 nished did they loiter about visiting flowers previous to 

 their return home. But the labours of the female and 

 neuter Bombi themselves are now over, and they would 

 therefore find no store whereon to deposit their eggs. 

 The parasitical allocation of these insects is as follows. 

 Apathus rupestris infests Bombus lapidarius ; A. vestalis 

 the B. terrestris, and this forms an instance in which 

 the parasite is not clothed in the colours of its sitos. 

 But A. Barbutellus has a wide range, for it frequents 

 the nests of B. pratorum, B. Derhamellus, and B. Skrim- 

 shiranus. 



