This result is deserving of attentive consideration. At the moment when I am inserting my beam, the insect has its mandibles engaged: they are holding the pellet of mortar intended for the blocking-operation. As the extracting-tool is not free, the extraction does not take place. I expected to see the Bee relinquish her mortar and then proceed to remove the encumbrance. A dab of mortar more or less is not a serious business. I had already noticed that it takes my Mason-bees a journey of three or four minutes to collect one. The pollen-expeditions last longer, a matter of ten or fifteen minutes. To drop her pellet, grab the straw with her mandibles, now disengaged, remove it and gather a fresh supply of cement would entail a loss of five minutes at most. The Bee decides differently. She will not, she cannot relinquish her pellet; and she uses it. No matter that the larva will perish by this untimely trowelling: the moment has come to wall up the door; the door is walled up. Once the mandibles are free, the extraction could be attempted, at the risk of wrecking the lid. But the Bee does nothing of the sort: she keeps on fetching mortar; and the lid is religiously finished. We might go on to say that, if the Bee were obliged to depart in quest of fresh mortar after dropping the first to withdraw the straw, she would leave the egg unguarded and that this would be an extreme measure which the mother cannot bring herself to adopt. Then why does she not place the pellet on the rim of the cell? The mandibles, now free, would remove the beam; the pellet would be taken up again at once; and everything would go to perfection. But no: the insect has its mortar and, come what may, employs it on the work for which it was intended. If any one sees a rudiment of reason in this Hymenopteron intelligence, he has eyes that are more penetrating than mine. I see nothing in it all but an invincible persistence in the act once begun. The cogs have gripped; and the rest of the wheels must follow. The mandibles are fastened on the pellet of mortar; and the idea, the wish to unfasten them will never occur to the insect until the pellet has fulfilled its purpose. And here is a still greater absurdity: the plugging once begun is very carefully finished with fresh relays of mortar! Exquisite attention is paid to a closing-up which is henceforth useless; no attention at all to the dangerous beam. O little gleams of reason that are said to enlighten the animal, you are very near the darkness, you are naught!