116 THE EVOLUTION THEORY 



One of the most beautiful examples of mimicry was discovered 

 by Gerstacker, not in free nature, but in the entomological collection 

 at Berlin. There he found beside a green, metallic weevil-beetle, one of 

 the Pachyrhynehidse from the Philippines, two other insects with the 

 same metallic sheen and very similar form of body. They had been 

 put in beside the weevil as duplicates, but more careful observation 

 showed that they were delicate Gryllidae, which mimicked the hard 

 beetles so deceptively that even the practised eye of the entomologist 

 was misled by them. Later on it was shown that these Gryllids live 

 in the Philippines beside the weevils, and even on the same leaves with 

 them, and that the beetles are protected from the attacks of birds and 

 other enemies by the extraordinary hardness of their cuticle. The 

 case is especially remarkable because in general the Gryllidae have no 

 metallic shimmer, and the form of body must have been considerably 

 altered to make them resemble the beetle. The usually broad head of 

 the Gryllids is in this case narrower, the usually flat wing-covers are 

 arched and pear-shaped, and the legs have become quite beetle-like. 

 The security enjoyed by the weevil must be very perfect, for it is 

 mimicked by three other species of beetle in the Philippines. 



Animals can also be protected from attack by the possession of 

 dangerous weapons. To this class belong insects with poisonous 

 stings, like the bees, wasps, and ants, and in some degree also the 

 ichneumon-flies. We cannot wonder, therefore, that these dreaded 

 species find imitators. In this case it is not of so much importance 

 that the copy should be rarer than the model, for anything that looks 

 like a dangerous insect will be avoided, since close investigation is in 

 this case attended with clanger. So we find that hornets, wasps, and 

 bees are frequently imitated by other insects, by beetles, flies, and 

 butterflies ; and these must derive a certain advantage, even when the 

 resemblance is only a general one. Many Longicorns, which visit 

 flowers, are striped black and yellow, like a wasp, and so are many 

 flies, like the species of Syrphws, and so on. The Longicorn Necy- 

 dalis major bears a strong resemblance to a large ichneumon-fly; it 

 has the same long-drawn-out body, the same swellings on the femur 

 and tibia, the curved antennae, the glossy brown colour, and its wing- 

 covers are quite short, leaving the wings free, so that the deception is 

 very complete. 



Bees, too, are sometimes so well imitated that they are hardly 

 to be distinguished from their mimics, not in flight only, but also 

 when visiting flowers. The best and commonest mimic of our honey- 

 bee is a perfectly harmless fly of the same size and colour, the drone- 

 fly (Eristalis tenax). The two are often to be seen together on the 



