vil DEFENCES OF INSECTS 259 



by Pieridae (Leptalis), which are quite- distinct from 

 their models in structural characteristics. The 

 Pieridae is the family to which our common Garden 

 Whites or Cabbage Butterflies belong. Like the 

 specimens at home non-mimetic species of South 

 America are white, and to these the mimetic * Pieridae 

 present a striking contrast. Different species imitate 

 those of the Heliconidae of the same district in the 

 form of the wings, every shade of colour and pattern 

 is copied, the imitation being carried out to such a 

 wonderful degree as to continually deceive the eyes of 

 the most experienced collectors. The mocking species 

 and the forms mocked usually fly in the same part of 

 the forest, and generally in company, to the evident 

 advantage of the Leptalis. And as if to derive all 

 possible benefit from the association, the mimicking 

 Pieridae are extremely scarce, while the Heliconidae 

 are very common, so that it seems hardly possible for 

 an enemy to detect the fraudulent insects, or that it 

 would take the trouble to detect them, even were it 

 aware of their presence. The excessive abundance of 

 the mimicked butterflies wherever they occur, indicates 

 the antiquity and the specially protected nature of 

 the species, and is exactly the characteristic to induce 

 the resemblance. 



Besides the Pieridae, a genus of quite another family 

 of pretty little American butterflies (Erycintdce) mimic 

 the specially protected and dominant forms. The 

 Swallow-tails (Papilio), and others, and certain genera 

 of diurnal moths likewise present species which often 

 copy the same favoured creatures. It sometimes 

 occurs in a district, that a species of Leptalis species 



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