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in PROTECTIVE RESEMBLANCES AMONG ANIMALS 61advantage to other insects to be mistaken for them. Thereis also another extraordinary fact that we are not yet in aposition clearly to comprehend some groups of the Heliconidaethemselves mimic other groups. Species of Heliconia:mimic Mechanitis, and every species of Napeogenes mimics1some other Heliconideous butterfly. This would seem toindicate that the distasteful secretion is not produced alikeby all members of the family, and that where it is deficientprotective imitation comes into play. It is this, perhaps,that has caused such a general resemblance among the Heliconidse,such a uniformity of type with great diversity ofcolouring, since any aberration causing an insect to cease tolook like one of the family would inevitably lead to its beingattacked, wounded, and exterminated, even although it wasnot eatable.In other parts of the world an exactly parallel series offacts have been observed. The Danaidse and the Acrseidse ofthe Old World tropics form in fact one great group with theHeliconidse. They have the same general form, structure,and habits ; they possess the same protective odour, and areequally abundant in individuals, although not so varied incolour, blue and white spots on a black ground being themost general pattern. The insects which mimic these arechiefly Papilios and Diadema, a genus allied to our peacockand tortoiseshell butterflies. In tropical Africa there is apeculiar group of the genus Danais, characterised by darkbrownand bluish-white colours, arranged in bands or stripes.One of these, Danais niavius, is exactly imitated both byPapilio hippocoon and by Diadema anthedon ; another, Danaisecheria, by Papilio cenea and in Natal a; variety of theDanais is found having a white spot at the tip of wings,accompanied by a variety of the Papilio bearing a correspondingwhite spot. Acrsea gea is copied in its very peculiarstyle of coloration by the female of Papilio cynorta, byPanopsea hirce, and by the female of Elymnias phegea. Acraeaeuryta of Calabar has a female variety of Panopea hirce fromthe same place which exactly copies it ;and Mr. Trimen, inhis paper on " Mimetic Analogies among African Butterflies,"1A satisfactory explanation of this phenomenon has now been found. SeeDarwinism, p. 252.