62 U.S. NATIONAL MUSEUM BULLETIN 2 65 



common hosts of C lucidus plagosus, but not the others, while the 

 spotted scrub wren, Sericornis maculatus, is recorded as victimized 

 by plagosus but not by basalis. On rare occasions both species of 

 cuckoos have been found to parasitize the same nest. 



We may now turn to each of the nine species of Clirysococcyx of 

 whose breeding habits we have some knowledge to determine the 

 extent to which each exhibits host-specific trends. 



1. C. malayamis: no information at all on the breeding habits for 

 6 of its races (aheneus, jungei, salvadorii, rnisoriensis , rujomerus, and 

 crassirostris) ; in 3 others (malayanus, albifrons, and poecilurus) 

 the only host records are for warblers of the genus Gerygone (G. 

 sulphur ea for malayanus and albifrons, G. magnirostris for poecilurus) , 

 but the total evidence is so slight that it cannot be said that other hosts 

 will or ^\dll not be found to be used ; in two races (russatus and minutil- 

 lus) the Gerygone warblers are the most usual, but by no means the 

 exclusive, hosts, with some 13 kinds of warblers, honey-eaters, etc. 

 (Gerygone, Heteromyias, Cyrtostomus, Meliphaga, Ptilotis, and others) 

 recorded as victims of russatus and 4 as victims of minutillus. 



2. C. lucidus: this species, in its various races, shows the whole 

 range of host selection from nonspecificity to individual host specificity 

 to specific host specificity. The importance of this variability merits 

 discussion here. 



That specific, as well as individual, host specificity may both occur 

 in different geographic segments of the same species of parasite 

 is shown by the Pacific-island races of C. lucidus, which appear to be 

 so restricted in theii* host choice to Gerygone that their distribution 

 is correlated with, if not governed by, the presence of these little gray 

 warblers as breeders. Thus, in his description and discussion of 

 C. lucidus layardi, Mayr (1932, p. 7) was led to -write that its distri- 

 bution "is apparently closely linked up \\dth that of its foster parent, 

 Gerygone jiavolateralis . . . . G.jl. correiae was found by the Whitney 

 Expedition on Mai, Epi, Lopeui, Ambrym, Malekula, Aoba, Gaua and 

 Vanua Lava. The collecting of one specimen of this cuckoo on Utupua 

 Island was a surprise. It is not kno\\Ti what species serves there as 

 foster-parent . . . ." Similarly, in his account of C. I. harterti, Mayr 

 (1932, p. 8) \^Tote that the "occurrence of a Bronze Cuckoo on Rennell 

 Island is obviously due to the presence of Gerygone on the same 

 island . . . ." Certainly this marked and exclusive degree of host 

 specificity is not true of the lucidus popidation that breeds in New 

 Zealand (typical lucidus), where two species of Gerygone (igata and 

 albqfrontata) are the chief, but not the only, hosts, which are known 

 to include forms of Rhipidura, Petroica, and Zosterops as well. Even 

 less is this true of the popidous segment of the species breeding in 



