A. Latreillii, without having a very large implement, also bears witness to the possibility of heaping up soft resin with a rake; she arms her mandibles with three or four sharply-cut teeth. In short, out of four Resin-bees, the only four that I know, one is armed with a spoon, if this expression be really suited to the tool's function; the three others are armed with a rake; and it so happens that the most copious heap of resin is just the work of the rake with the most teeth to it, a tool suited to the cotton-reapers, according to the views of the Bordeaux entomological expert. No, the explanation that appealed to me so much at first is not admissible. The mandible, whether supplied with teeth or not, does not account at all for the two manufactures. May we, in this predicament, have recourse to the general structure of the insect, although this is not distinctive enough to be of much use to us? Not so either; for, in the same stone-heaps where the Osmia and the two Resin-bees of the Snail-shells work, I find from time to time another manipulator of mastic who bears no structural relationship whatever to the genus Anthidium. It is a small-sized Mason-wasp, Odynerus alpestris, SAUSS. She builds a very pretty nest with resin and gravel in the shells of the young Common Snail, of Helix nemoralis and sometimes of Bulimulus radiatus. I will describe her masterpiece on some other occasion. To one acquainted with the genus Odynerus, any comparison with the Anthidia would be an inexcusable error. In larval diet, in shape, in habits, they form two dissimilar groups, very far removed one from the other. The Anthidia feed their offspring on honey-bread; the Odyneri feed it on live prey. Well, with her slender form, her weakly frame, in which the most clear-seeing eye would seek in vain for a clue to the trade practised, the Alpine Odynerus, the game-lover, uses pitch in the same way as the stout and massive Resin-bee, the honey-lover. She even uses it better, for her mosaic of tiny pebbles is much prettier than the Bee's and no less solid. With her mandibles, this time neither spoon nor rake, but rather a long forceps slightly notched at the tip, she gathers her drop of sticky matter as dexterously as do her rivals with their very different outfit. Her case will, I think, persuade us that neither the shape of the tool nor the shape of the worker can explain the work done.