160 ASSOCIATION OF ORGANISMS—THE WEB OF LIFE 
rently well-authenticated instances of this among digging wasp- 
like forms (Cevcerzs), Saw-Flies, Bees, and even Butterflies. 
Tue Law or 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- 
