26 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I46 



Eudynamis scolopacea, in northern India, may have influenced the 

 eastward emigration of early glandarhis to areas free from such 

 difficulties. 



The close resemblance between the eggs of the great-spotted cuckoo 

 and of the magpie is evidence of a long continued and very specialized 

 host-parasite relationship. As Baker (1942, p. 85) wrote, the parasite 

 lays, ". . . one type of egg and one type only which is so exactly like 

 in colour, shape, and superficial appearance of texture to that of 

 the Magpie that identification is generally extremely difficult , . ." 

 It may be stressed at this time that the egg, speckled with dusky, is a 

 highly "advanced" egg type for a cuckoo, the basic, primitive egg type 

 in the family being unmarked white, and it has arrived long ago at 

 a stage far beyond the development evinced in any other species of 

 Clamator. That it is "fixed" and invariable, and that it now persists 

 unchanged in the vast stretches of sub-Saharan Africa, where it does 

 not match the eggs of the hosts used there, is evidence for the age 

 and the finality of this "end product" of adaptive evolution. 



If we were to assume, without documentation, as Voous (1960, p. 

 154) has done, that C. glandarius originated in sub-Saharan Africa 

 and hence, that it there evolved its egg type in the absence of any 

 known host whose eggs it resembled, and then later invaded Mediter- 

 ranean Africa and the Iberian Peninsula, where its eggs "fitted" 

 so well with those of the magpie, we would have a most remarkable 

 example of extreme preadaptation. It would be so remarkable that it 

 would be difficult to accept it without extremely disturbing doubts and 

 skepticism. 



If, on the other hand, it be accepted, as here postulated, that 

 Clamator glandarius, having arrived at a perfected stage of adaptive 

 evolution with regard to the degree of similarity of its eggs to those 

 of the magpie, its chief, and almost its only, host in Asia Minor, in 

 the Iberian Peninsula, and in northwestern Africa, then expanded its 

 range southward into areas where this adaptive excellence no longer 

 had its former value, we would have a case of what may be called 

 "repudiative evolution." Part of the species acted as though the 

 matter of egg resemblance no longer mattered, and in its new home 

 used new fosterers to which it was not adapted. In a sense, this 

 amounted to an escape from too specialized a form of host relation- 

 ship ; one which, had it been adhered to, would have markedly limited 

 the parasite geographically, for the cuckoo is a bird of warm climes, 

 whereas the magpie's range extends far to the north where the 

 parasite would not be able to follow it, and the two are sympatric 

 only in a limited area. 



