FLIES. 181 



single pair of wings, are so like bees (in which, it need 

 scarcely be said, there are two pairs of wings) that it is 

 "very difficult to persuade some persons that they are not 

 really members of that group of insects. Their resemblance 

 to the latter is increased by their similar habits, more 

 especially their bee-like buzz ; and there is no doubt 

 whatever but that they are mistaken by birds for bees, 

 and thereby enjoy an immunity not granted to ordinary 

 flies. An allied kind of fly (Vohicella) goes even farther 

 than this.a.nd actually deceives the humble-bees themselves, 

 which it closely resemltles both in form and coloration. 

 The object of this mimicry is to enable these flies to pass 

 freely in and out of the nests of humble-bees in order to 

 deposit their eggs, which eventually hatch into larvse 

 whose food are the grubs of the bees. Again, the gaudy 

 flies marked with bold bands of black and yellow which 

 are so common on fine summer days in gardens, aud are 

 known as wasp-flies (Siirphus) , take their name from their 

 resemblance to wasps, which in some species is so close as 

 to make it difficult to convince people that they are not 

 really wasps. 



Less common than the above-mentioned flies are the 

 beautiful British insects known as clear-winged hawk- 

 moths. Some of these, named hornet clear- wings (Sphecia), 

 so exactly resemble large wasps or hornets that they would 

 deceive nine persons out of ten who are not entomologists. 

 Moreover, they have exactly the same habits as hornets, 

 and when caught will actually curl up their bodies in a 

 wasp-like manner as if about to sting, although they are 

 perfectly harmless. Less complete is the resemblance of 

 other clear-wings — hence known as bee-clear-wings — to 

 humble-bees. These insects, as has been well observed, 

 are, however, very imjjortant, as proving that their mimicry 

 is an acquired character, since when they first emerge from 

 the chrysalis their wings are thinly covered with the well- 

 known minute scales characteristic of ordinary moths, 

 these scales soon falling off and leaving the wings per- 

 fectly transparent. This indicates that the ancestors of 

 the clear-wings had wings like other moths. 



In all the foregoing instances the mimicking insects 



