272 SECRETS OF ANIMAL LIFE 
in considering the maternal care of some of the 
worker-ants and worker-bees, who are normally 
non-productive females. They mother the young 
as if these were their own, and we explain this by 
the natural supposition that this capacity dates 
back to the time when all the females were normally 
mothers, before the communal life with its marked 
division of labor was established. It may be re- 
membered that fertile workers occasionally occur, 
and that a worker grub can be nurtured into a 
queen. We cannot suppose that the workers simply 
inherit their nursing capacities from their mother 
—the queen—for she does not exhibit the qualities 
required, being specialized for sheer maternity. We 
must go much farther back. Another illustration 
of our argument may be found in a widely different 
sphere—in the case of the European cuckoo. In a 
somewhat elaborate way the mother-bird secures 
the success of offspring to which she is herself a 
stranger. Laying her egg on the ground, she takes 
it in her mouth, flies with it down the hedgerow, 
and puts it into the selected nest of a foster-parent, 
and thus hits an unseen mark. The existence of 
other kinds of cuckoo which show less perfect 
evasion of parental duties convinces us that the 
utilization of other nests and of foster-parents was 
gradually evolved from a state of affairs in which 
cuckoos reared their own young. The egg has 
significance to the mother-cuckoo, who has no 
experience of nestling or chick, because she belongs 
to a race in which brooding was once the rule. 
