A RAMBLE UP BURNHOPE. lOI 



always seem so much more abundant than the males. I 

 spent some time catching them in search of males, but without 

 success. 



Here I was much interested in the capture of a Volucella 

 ( V. bombylans, L., var. haemorrhoidalis, Ztt.). Though I 

 believe common in many places, it is not very common in 

 this district, and this was the first of this light coloured variety 

 that I had taken. I was especially interested in this species, 

 because it supplies such a good instance of mimicry, and such 

 a puzzling one. It occurs in two well marked varieties, the 

 dark Bombylans variety, which I had taken further down 

 Weardale, and this lighter one. The former mimics the black 

 and red bee, Bombus lapidarms^ L., which it strongly 

 resembles ; the latter, which I had just caught, mimics the 

 brownish grey bee, B. agrorum, Fab., and it is so like the 

 bee that I had almost passed it over had not an unbeelike 

 set of the wings caused me to look more closely. Both 

 varieties frequent, indiscriminately, the nests of both bees for 

 the purpose of laying their eggs, that their young may feed on 

 the food laid up by the bee for its own offspring, and possibly 

 on that offspring itself, or, perhaps — and I think this is more 

 likely considering the usually scavenger office of most fly- 

 larvse — on the dead bee-larvae. It is easy to understand how 

 the fly would be protected by its likeness to one or other 

 species of bee, and if the fly had developed into two species, 

 each keeping to its own host, there would have been no 

 difficulty. But the light fly, as well as the dark one, goes 

 into the home of the dark bee, to which it has no resem- 

 blance, and vice-versa. Where is its protection ? And 

 besides, another Volucella (pelhicens, L.), several of which 

 were darting about, frequents the nests of wasps which it 

 does not resemble in the slightest degree. 



But such thoughts had .soon to give place to other objects 

 of interest. Crossing a fence out of the woody slope I found 

 myself at the foot of a precipice of shale, surmounted by 

 great massive blocks of sandstone, which, the map told me, 

 was the Nattrass Gill Hazle. The shales were soft and had 



