DIFFERENTIATION, MIGRATION, AND MIMICRY. 381 



even of birds, compared with the countless species of inverte- 

 brates. Out of the vast assemblage of insects, with their varied 

 colours and patterns, it would be strange if there were not many 

 cases of accidental resemblance. A strict application of Wallace's 

 five laws would, perhaps, if all the circumstances were known, 

 eliminate many accepted instances. 



As to cases of edible insects mimicking inedible ones, Mr. 

 Poulton admits that even unpalatable animals have their special 

 enemies, and that the enemies of palatable animals are not in« 

 definitely numerous. 



Mr. Beddard gives tables of the results obtained by Weismann, 

 Poulton, and others, which show that it is impossible to lay down 

 any definite law upon the subject, and that the likes and dislikes 

 of insect-eating animals are purely relative. 



One of the most interesting cases of mimicry is that of the 

 Volucella, a genus of Diptera, whose larvae live on the larvse of 

 Hymenoptera, and of which the perfect insect closely resembles 

 some species of humble-bee. Though this fact is unquestioned, 

 yet it has recently given rise to a controversy, which, so far as 

 one who has no claim to be an entomologist can judge, proves 

 that, while there is much that can be explained by mimicry, there 

 is, nevertheless, a danger of its advocates pressing it too far. 

 Volucella bombylans occurs in two varieties, which prey upon the 

 humble-bees, Bombus muscorum and B. lapidarius, which they 

 respectively resemble. Mr. Bateson does not question the be- 

 haviour of the Volucella, but states that neither variety specially 

 represents B. muscorum, and yet that they deposit their eggs more 

 frequently in their nests than in the nests of other species which 

 they resemble more closely. He also states that in a show-case in 

 the Royal College of Surgeons, to illustrate mimicry, two specimens 

 of another species, B. sylvarum, were placed alongside of the Volu» 

 cella, which they do resemble, but were labelled B. muscorum. 



But Mr. Hart explains the parasitism in another way. He 

 states that a nest of B. muscorum is made on the surface, without 

 much attempt at concealment, and that the bee is a peculiarly 

 gentle species, with a very feeble sting ; but that the species 

 which the Volucella most resemble are irascible, and tberefore 

 more dangerous to intruders. If this be so, it is difficult to see 

 why the Volucella should mimic the bee, which it does not affect, 

 more closely than the one which is generally its victim* I do not 



