64 NATURAL SELECTION in 



another moth, Diaphora mendica, which appears about the 

 same time, and whose female only is white. It is about the 

 same size as Spilosoma menthastri, and sufficiently resembles 

 it in the dusk, and this moth is much less common. It seems 

 very probable, therefore, that these species stand in the same 

 relation to each other as the mimicking butterflies of various 

 families do to the Heliconidse and Danaidse. It would be very 

 interesting to experiment on all white moths, to ascertain if 

 those which are most common are generally rejected by birds. 

 It may be anticipated that they would be so, because white 

 is the most conspicuous of all colours for nocturnal insects, 

 and had they not some other protection would certainly be 

 very injurious to them. 



Lepidoptera mimicking other Insects 



In the preceding cases we have found Lepidoptera imitat- 

 ing other species of the same order, and such species only as 

 we have good reason to believe were free from the attacks of 

 many insectivorous creatures ; but there are other instances 

 in which they altogether lose the external appearance of the 

 order to which they belong, and take on the dress of bees or 

 wasps insects which have an undeniable protection in their 

 stings. The Sesiidas and ^geriidse, two families of day-flying 

 moths, are particularly remarkable in this respect, and a mere 

 inspection of the names given to the various species shows 

 how the resemblance has struck every one. We have api- 

 formis, vespiforme, ichneumoniforme, scoliseforme, sphegi- 

 forme (bee -like, wasp -like, ichneumon -like, etc.), and many 

 others, all indicating a resemblance to stinging Hymenoptera. 

 In Britain we may particularly notice Sesia bombiliformis, 

 which very closely resembles the male of the large and 

 common humble bee, Bombus hortorum; Sphecia craboni- 

 forme, which is coloured like a hornet, and is (on the 

 authority of Mr. Jenner Weir) much more like it when alive 

 than when in the cabinet, from the way in which it carries its 

 wings; and the currant clear- wing, Trochilium tipuliforme, 

 which resembles a small black wasp (Odynerus sinuatus) very 

 abundant in gardens at the same season. It has been so 

 much the practice to look upon these resemblances as mere 

 curious analogies playing no part in the economy of nature, 



