THE AUSTRALIAN NATURALIST. 199 
wasp larvae. The wasp egg is placed on the first spider 
placed in the cell, and the spiders are eaten one by one in 
the order in which they are placed in the cell. The cell is 
sealed up when full, and the young grub left to develop 
within until it emerges as a full-grown wasp. In the three 
nests I observed, one cell was always left empty and un- 
capped by the wasp. “Whether it was used as a place of 
shelter or as a place from which the adult wasp kept a 
watch over the nest my observations do not permit me to 
say, but nevertheless seem to me to be connected in some 
way with the economy of the nest. ‘ 
Perhaps the most amazing part of all the interesting 
behaviour of the solitary wasps is the habit of stinging 
their prey only to paralyse and not to kill it. The ad- 
vantage of this is obvious. If killed the prey would 
quickly decompose, and the hatching wasp larva would 
only have, to it, inedible decaying flesh, instead of the 
fresh live animal substance it demands. On the other 
hand, if the prey were stored unhurt, it would, if active 
enough, quickly escape from the burrow or would sue- 
ceed in unconsciously crushing the delicate wasp-ege by 
wriggling about in the underground prison cell. As it is 
with the paralysed prey, there is no exertion, decomposi- 
tion is absent, and life without food is capable of being 
prolonged several days. The paralysis is due to the sting- 
ing by the wasp of one or more of the nerve centres of 
the ventral nerve cord. Insects thus paralysed will keep alive, 
flexible, fresh, and immovable, as Fabre has observed, for 
a period of six weeks, a much longer period than is neces- 
sary for the development of any wasp larvae. The expert- 
ness and accuracy displayed by the wasp in plunging the 
sting exactly into those parts. the injury of which brings 
about just that ideal condition of the prey necessary for 
the sustenance of the wasp larvae, has led some writers to 
credit the solitary wasps with such human attributes as 
reason and consciousness. The whole behaviour, however, 
is perhaps inore satisfactorily explained as the result of 
a complex reflex or instinetive action. Sinilarly the 
whole course of nest building, previously described, is a 
performance wholly for the sake of the young, which the 
‘mother will probably never see; and these young in turn 
