160 ASSOCIATION OF ORGANISMS THE WEB OF LIFE 



rently well -authenticated instances of this among digging wasp- 

 like forms (Cerceris), Saw- Flies, Bees, and even Butterflies. 



THE LAW OF BEAUTY. Male insects, especially Butterflies, are 

 often more beautiful and more conspicuous than individuals of the 

 other sex, but it is necessary here to be cautious in drawing 

 conclusions, for courtship is not the only business of life. That 

 the female should often be in plain attire would often appear to be 

 a protective measure, as it is more important for the welfare of the 

 species that she should escape from enemies than her comparatively 

 useless partner. The same explanation may be given where 

 female butterflies are conspicuous as the result of protective mimi- 

 cry (see vol. ii, p. 311). This line of argument, however, may 

 easily be carried too far, and the usually brighter colours of the 

 male in insects (and other animals) cannot be satisfactorily ex- 

 plained simply as one of the results of greater energy and activity. 

 In many groups the eyes are complex and highly developed, and 

 that they often minister to a " colour-sense " is generally admitted, 

 the relations between insects and flowers, for example, affording 

 much evidence in this direction (see p. 85). Admitting this, 

 Wallace suggests that his theory of recognition marks (see pp. 

 132, 140) may account for many of the distinctive colours and 

 markings of insects. In arguing against this view Poulton says 

 (in The Colours of Animals] " that the beauty of the colours and 

 patterns displayed in courtship can never be explained by this 

 principle. For the purposes of recognition, beauty is entirely 

 superfluous and indeed undesirable; strongly -marked and con- 

 spicuous differences are alone necessary. But these, which are 

 so well marked in Warning Colours, are not by any means 

 characteristic of those displayed in courtship. If an artist, 

 entirely ignorant of natural history, were asked to arrange all the 

 brightly-coloured butterflies and moths in England in two divi- 

 sions, the one containing all the beautiful patterns and combina- 

 tions of colour, the other including the staring, strongly-contrasted 

 colours, and crude patterns, we should find that the latter would 

 contain, with hardly an exception, the species in which independent 

 evidence has shown, or is likely to show, the existence of some 

 unpleasant quality. The former division would contain the 

 colours displayed in courtship and when the insect is on the 

 alert, concealed at other times. The immense difference between 

 the two divisions, the one most pleasing, the other highly repug- 



