232 ANIMAL COLOEATION. 



case of mimicry, whicli does not fall in witli this paragraph 

 in Mr. Wallace's definition of mimicry. The insect in 

 question is the Bee-fiy {Eristalis tenax),* which, although a 

 Dipteron — possessing two wings — has a strong superficial 

 likeness to a bee. It frequents flowers just as bees do, but 

 has a more lethargic disposition than the active hive bee which 

 it imitates. Now, this insect is extremely common, and has 

 even in recent times extended its range to many distant parts 

 of the world. Experiments, moreover (see p. 165), have shown 

 that it is not systematically rejected by insect-eating animals. 



Criticism of an Apparent Case of Mimicry. 



Dr. Seitz gives several interesting cases of mimicry among 

 Lepidoptera in Germany, some of which, however, appear to me 

 to be open to criticism. He calls attention, for example, to 

 a moth which mimics one of the day -flying Yellow Underwings 

 (Brephos nothurri); or rather, he emphasises the resemblance 

 between B. iiothum and Ploseria ditermta without being in 

 a position to say which is " original " and which " copy." " If 

 it were strange," remarks Dr. Seitz, " that two not nearly 

 related species are found in March, an unusual month for 

 moths, so much so that on fine spring days these insects are 

 generally the only two met with — it would be carrying scepti- 

 cism too far to regard the agreement between the species as 

 merely the result of accident." This is plausible, but not 

 entirely convincing, if we take other facts into account. 

 Mr. Ponlton, in arguing for the efficacy of warning colours (and 

 of course this will include mimicry), points out " the entire 



* It is an interesting fact, in connection witli the resemblance between 

 this fly and a hive bee, that it feeds upon pollen and honey. This fact 

 ■may have some significance in relation to the efiEects of food upon form 

 and coloration (see p. 48). For a discussion of the food of this fly see 

 Entomologist, vol. vi., p. 336. 



