There are, as a matter of fact, some pompilids which, instead of hunting, lay their eggs upon the victim which their congeners carry to the nest. The first observations concerning this change of habit are due to J. Perez. Having seen a Ceropales maculata trying to lay its egg on a spider which a Pompilus rufipes was carrying, the lamented professor suspected a new phenomenon and was happy enough soon to find an egg upon the victim of a certain pompilid which had been laid by a Ceropales. This was almost a confirmation of views advanced from Dahmom to :Taschenberg. "The Ceropales he concludes,«are parasites of the pompilids."
Ferton had the good fortune, which he merited more than any one else, of following this little entomological drama to its last act. His first two observations resemble the two observations of Perez, but in the second he was able to follow the egg on the spider and obtained a Ceropales maculata. The third is still more interesting and should be quoted :
A Pompilus chalybeatus, watched 'by a little Ceropales cribrata, was carrying to its nest a large Lycosa. At the moment when the spider disappeared in the hole, the Ceropales arrived, entered into the nest after the load, and remained there a few seconds. I collected the wasp and the victim, the latter bearing the eggs of the Pompilus. Six days later the egg . . . shriveled, and the embryo already formed, did not reach the hatching-point, but I found two days after the larva of the Ceropales which was attached under the abdomen of the spider. The latter had revived, and lived during the whole repast of the larva.
Most of the Ceropales, if not-at all, have similar habits. In the United States the Peckhams found two individuals of this- genus harassing a Pompilus scelestus which was carrying an enormous lycosid. They captured it instead of noting the subsequent events, which was unfortunate, since Adlerz has' stated that the Ceropales hides its egg in the narrow lung-chamber of the spider.