218 INSTINCT. Chap. VII. 



generated. I may add that, according to Dr. Gray 

 and to some other observers, the European cuckoo has 

 not utterly lost all maternal love and care for her own 

 offspring. 



The occasional habit of birds laying their eggs in 

 other birds' nests, either of the same or of a distinct 

 species, is not very uncommon with the Gallinaceae ; 

 and this perhaps explains the origin of a singular 

 instinct in the allied group of ostriches. For several 

 hen ostriches, at least in the case of the American 

 species, unite and lay first a few eggs in one nest and 

 then in another ; and these are hatched by the males. 

 This instinct may probably be accounted for by the fact 

 of the hens laying a large number of eggs ; but, as in 

 the case of the cuckoo, at intervals of two or three days. 

 This instinct, however, of the American ostrich has not 

 as yet been perfected ; for a surprising number of eggs 

 lie strewed over the plains, so that in one day's hunting 

 I picked up no less than twenty lost and wasted eggs. 



Many bees are parasitic, and always lay their eggs in 

 the nests of bees of other kinds. This case is more re- 

 markable than that of the cuckoo ; for these bees have 

 not only their instincts but their structure modified in 

 accordance with their parasitic habits ; for they do not 

 possess the pollen-collecting apparatus which would be 

 necessary if they had to store food for their own young. 

 Some species, likewise, of Sphegidae (wasp-like insects) 

 are parasitic on other species ; and M. Fabre has lately 

 shown good reason for believing that although the 

 Tachytes nigra generally makes its own burrow and 

 stores it with paralysed prey for its own larvae to feed 

 on, yet that when this insect finds a burrow already 

 made and stored by another sphex, it takes advantage 

 of the prize, and becomes for the occasion parasitic. In 

 this case, as with the supposed case of the cuckoo, I can 



