WARNING COLOURS AND MIMICRY 155 



The case of DismorpMa praadnoe is by no means 

 isolated. Examples of mimicry among butterflies are 

 now known by hundreds, not only in South America, but 

 in all the warmer regions of the globe. In some instances 

 as many as a dozen weaklings, including day-flying moths, 

 are attached mimetically to a single dominant distasteful 

 type. Yet we must not assume that the mere fact of one 

 insect's resemblance to another necessarily constitutes a 

 case of mimicry. Uniformity of habit and environment 

 may, on occasion, lead to uniformity of appearance. 

 There are instances on record of insects indigenous to 

 countries extremely remote which might well be put for- 

 ward as examples of mimicry if a likeness in form and 

 colour were the only test. Even when two similarly 

 coloured insects are found in the same country, the mere 

 fact of a mutual resemblance proves nothing. We have in 

 England two totally distinct moths known as the marvel- 

 du-jour {Agriopis aprlUna) and the scarce marvel-du-jour 

 (Dipthera oriori). The former is common, the latter com- 

 paratively rare, as its popular name implies. In each 

 the fore-wings are beautifully mottled with green, inter- 

 spersed with black and white markings, while the hind- 

 wings are smoky-grey. A hastily formed judgment 

 might lead us to conclude that one insect is mimicked by 

 the other ; but the fallacy of such a notion is evident 

 when we learn that whereas the scarce marvel-du-jour 

 flies in June, the common marvel-du-jour does not appear 

 until October. Both moths, however, rest during the day 

 upon tree trunks, and in this position they resemble the 

 same kind of green lichen. Thus the similarity of the two 

 species is clearly due to their likeness to a common object. 

 To establish a case of mimicry it is necessary to show in 

 the first place that one of the insects, the model, really 

 possesses some hurtful or nauseating quality that renders 



