esults from the position in which the hymenopterous
insect maintains its victim; for the sting is on the median line, and
can only penetrate at the soft points; the two points attacked are
then rigorously determined by physical circumstances. But these
arguments have no bearing if we consider the method of procedure
adopted by the _Ammophila_,[74] a hymenopterous insect related to the
preceding, which paralyses caterpillars. It is free in this case to
insert its sting at any portion of the body; yet it knows how to turn
over and arrange the captive so that the dart shall penetrate both
times at two points where ganglia will be poisoned and immobility
without death be induced. It must then be agreed that there is here an
instinct much too sure to be called mechanical; but these facts, which
considered alone seem simply marvellous, become much less so, and lend
themselves to evolutionary interpretation, when it is recognised that
they are related by insensible degrees to other facts of the same
order, much more intelligent and at the same time less sure.

[74] Paul Marchal, "Observations sur _l'Ammophila affinis_,"
_Arch. de Zool. exp. et gener._, ii. Serie, t. x., 1892.

_Similar cases in which the specific instinct is less powerful and
individual initiative greater._--Here is, for instance, the case of
the _Chlorion_, where each animal possesses more considerable
initiative.[75] It attacks the Cockroach. These insects are of an
extremely varied size, according to age, and as they are also very
agile the _Chlorion_ is not certain of being always able to obtain
victims of the same dimension. The orifice of its burrow, which it
hollows in walls between the crevices of the stones, is calculated on
the average size of its victims. It has also the habit of paralysing
the cockroach by stinging it on the nervous chain. These preliminary
operations do not impede it, but it is embarrassed when it wishes to
introduce through the entrance of its gallery an insect which is too
large. It pulls at first as much as it can, but seeing the failure of
its efforts it does not persevere in this attempt, and comes out to
survey the situation. Decidedly the victim is too large and cannot
pass through. The _Chlorion_ begins by cutting off the elytra, which
maintain it rigid and prevent it from being compressed. This done, it
harnesses itself anew and re-commences its efforts. But this is not
sufficient, and the victim still resists