266 COLOURATION OF REPTILES AND AMPHIBIANS. 



When I was able to collect my thoughts, I examined the 

 ground beneath the tree for further evidence, in the shape of 

 butterflies' wings, but found none. Of course, they could have 

 been easily carried away by the wind or by ants. 



Recognition (Episematic) Colours. 



Mr. A. R. Wallace believed that one of the chief jjurposes of 

 sexual colouring is to enable the sexes to recognize their kind, and 

 thus avoid the evils of infertile crosses. This I believe is a very 

 important factor in the colours of our Agamas and Zoniiriis. 

 \^ery often I have seen A. aculcata on stones fringing the kopjes 

 which form the retreat of A. atra, and on a few^ occasions I have 

 seen A. atra on stones right in the domain of A. aculcata. Now 

 A. atra and .i. aculcata are rather closely allied species, and the 

 fact that they are normally topographically separated may ])er- 

 ■haps mean that only in this way can they permanently maintain 

 their specific entities. If this be so. it is obvious that distinctive 

 colouration may be of great importance in preventing inter- 

 crossing by venturesome individuals which inay happen to over- 

 step the boundary line between the two areas. 



No direct proof of this explanation can be presented, but 

 having witnessed the display of a male Zoiiurus and the approach 

 of a female to him from a distance, it is difficult to avoid the con- 

 clusion that the brilliant red colours of that lizard serve for recog- 

 nition purposes ; it should Ije mentioned, however, that the females 

 are coloured like the males, Ijut not so brilliantly. In this species 

 the males and females live strictly apart, the intervening distance 

 between their respective retreats being sometimes as much as sixty 

 or seventy yards : in such cases it is probable that the sexes need 

 a means of distinguishing their kind from a distance, more 

 especially as they live in such close companionship with Agaiiia 

 atra. The corresponding blue in the males of the latter have in 

 all probability the same meaning. Supposing these colours did 

 not exist, then either sex of Agama or Zonurus in search of a 

 partner would be very often disappointed, as the manner of sit- 

 ting on the tops of the rocks is identical in both. And since they 

 orientate with the sun, the colour is seen from all points in the 

 course of a day. 



Mr. Wallace,* in dealing with colours which are an indication 

 of sexual maturity, made the following genera! statement :- — 



I see in the need of outward markings, whether for purposes of recog- 

 nition or as preventing inter-crossing between incipient species, a sufificient 

 cause for all such conspicuous indications of specific diversity as are found 

 pervading the whole vast world of life. 



Variable Protective (Procrvptic) Resemblance. 



It would appear that the power to change their colour to suit 

 the surroundings is much more common among the reptiles and 

 amphibians than is generally supposed. 



*World of Life, 165. 



