The renewal of a test is not sufficient: we must also vary our test. Let us, then, examine the insect's intelligence from another point of view, that of the introduction of foreign bodies into the cell. The Mason-bee is a housekeeper of scrupulous cleanliness, as indeed are all the Hymenoptera. Not a spot of dirt is suffered in her honey-pot; not a grain of dust is permitted on the surface of her mixture. And yet, while the jar is open, the precious Bee-bread is exposed to accidents. The workers in the cells above may inadvertently drop a little mortar into the lower cells; the owner herself, when working at enlarging the jar, runs the risk of letting a speck of cement fall into the provisions. A Gnat, attracted by the smell, may come and be caught in the honey; brawls between neighbours who are getting into each other's way may send some dust flying thither. All this refuse has to disappear and that quickly, lest afterwards the larva should find coarse fare under its delicate mandibles. Therefore the Mason-bees must be able to cleanse the cell of any foreign body. And, in point of fact, they are well able to do so. I place on the surface of the honey five or six bits of straw a millimetre in length. (.039 inch.--Translator's Note.) Great astonishment on the part of the returning insect. Never before have so many sweepings accumulated in its warehouse. The Bee picks out the bits of straw, one by one, to the very last, and each time goes and gets rid of them at a distance. The effort is out of all proportion to the work: I see the Bee soar above the nearest plane-tree, to a height of thirty feet, and fly away beyond it to rid herself of her burden, a mere atom. She fears lest she should litter the place by dropping her bit of straw on the ground, under the nest. A thing like that must be carried very far away.