The Volucella 



without danger, on the paper wall. No one 

 will know of her presence. The dangerous 

 thing is to cross the threshold of the burrow 

 in broad daylight, before the eyes of those 

 who go in and out. At that moment alone, 

 protective mimicry would be convenient. 

 Now does the entrance of the Volucella into 

 the presence of a few Wasps entail such very 

 great risks? The Wasps'-nest in my en- 

 closure, the one which was afterwards to 

 perish under a bell-glass in the sun, gave me 

 the opportunity for prolonged observations, 

 but without any result upon the subject of my 

 immediate concern. The Volucella did not 

 appear. The period for her visits had 

 doubtless passed; for I found plenty of her 

 grubs when the nest was dug up. 



Other Flies rewarded me for my assiduity. 

 I saw some — at a respectful distance, I 

 need hardly say — entering the burrow. 

 They were insignificant in size and of a dark- 

 grey colour, not unlike that of the House-fly. 

 They had not a patch of yellow about them 

 and certainly had no claim to protective mim- 

 icry. Nevertheless, they went in and out as 

 they pleased, calmly, as though they were at 

 home. So long as there was not too great 

 a number at the door, the Wasps left them 

 alone. When there was anything of a 



297 



