100 
[ October, 
ON AN UNDEFINED FACULTY IN INSECTS* 
EY J. II. EAEEE. 
Ammophila , boring its mine until a late hour of the day, abandons 
its work after having closed the opening of it with a stone, rambles 
from one flower to another, goes to a distance, and yet knows how r to 
return on the next day with its caterpillar-prey to the excavated 
domicile, although the localities may be new and unknown. Bembex, 
laden with its prey, falls with almost mathematical precision on the 
threshold of its doorway obstructed with sand and confused with the 
rest of the sandy covering. Where my observation and memory are 
defective, their coup cV ceil and remembrance have a certainty which is 
all but infallible. It may be said that there is in an insect something 
more subtle than the simple faculty of remembering — a kind of in- 
tuition of localities without analogy in man — in fact, an undefinable 
faculty which I term memory, for want of an expression to designate 
it. The unknown cannot have a name. In order, if possible, to 
throw a little light on this point of the psychology of animals, I insti- 
tuted a series of experiments. 
The first had for its subject Cerceris tuberculnta , the hunter of the 
Cleoni. About ten o’clock in the morning, I captured twelve females 
which were occupied on the same slope, in the same bourgade , either 
in excavating or provisioning the burrows. Each prisoner was sepa- . 
rately enclosed in a cornet of paper, and the whole were put in a box. 
I then went about two kilometres from the nests and there released 
the Cercerides , first taking care, in order to recognise them hereafter, 
to mark each one with a white spot in the middle of the thorax by 
means of the end of a straw dipped in indelible colour. 
The Cercerides flew only a few paces in all directions, to and fro ; 
rested on the sprigs of the herbage, passed for a moment their anterior 
tarsi over their eyes, as if dazzled by the bright sunshine into which 
they were suddenly brought, then took flight, some sooner others later, 
and all, without any hesitation, went in a direct line towards the south, 
that is to say, in the direction of their home. Five hours later I 
revisited the place where the nests are common, and, on arrival, saw 
two of my Cerceris with the white mark working at the burrows ; soon 
after a third came into the field with a Cleonus between its feet ; and 
a fourth soon followed. Four out of twelve in less than a quarter of 
an hour were enough for conviction, and I deemed it useless to prolong 
my attention. What four had known how to do the others would do 
* Translated from “ Souvenirs entomologiques.” Vide page 117, post. 
