64 NATURAL SELECTION Ill 
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 Heliconide and Danaide. 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 Sesiide and Aigeriide, 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, scolizforme, 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, 
