Each of the included leafy cells was one and one-eighth inches in length, and just barely exceeding one-fourth in width. Elliptical pieces of Spiræa, less in size than those previously described, but arranged in a similar manner, composed the several structures. Within each, a dead but perfectly-formed Megachile, encased in a cylindrical bag of silk, was found, so that there could be no possible doubt of the builder. That this inner fabric was the labor of some mother Megachile admits not of a scruple, for no other bee is known to construct a nest of like character. But what of the outer enveloping fabric of mud? It was clearly impossible for the skill of a Megachile, who, while certainly fitted for tunnelling the ground and for snipping circular and elliptical pieces of suited dimensions from leaves with all a tailor’s precision, would find herself wofully unadapted for the making of mortar and the building of nests, in imitations of tunnels, out of pellets of mud that had to be moulded into consistency and shape by the jaws of the builder. Pelopæus alone, of all hymenopters, possesses the ability and means of making such structures. Megachile, who is known to occasionally build under the boards of the roof of a piazza, might sometimes in her quest of a place appropriate the discarded cells of some pre-existent Pelopæus for nesting purposes, but she runs a very great risk in so doing, for the Mud-dauber does not always build a fresh home for her treasures, save when there is a lack of the last year’s structures. Old nests, when found, are put in speedy repair and made to do as invaluable a service. BATTLE BETWEEN ANTS. Whilst reclining one beautiful May afternoon in the shade of an oak that stood on the outskirts of a thicket, my attention was arrested by the activity and bustle presented by a colony of yellow ants, which proved to be the _Formica flava_, so common everywhere. Scattered indiscriminately about were numberless larvæ in various stages of growth, and not a few immobile pupæ, that had been brought up from subterranean domiciles by thoughtful nurses, while here and there were a dozen or more ants, but recently escaped from their mummy-cases, basking in the sun’s warmth, preparatory to entering upon the duties of the formicarium. The very picture of restlessness and anxiety were these full-grown neuters. That something was transpiring, or was about to transpire, seemed not unlikely, for ovæ, larvæ and pupæ were being quickly carried to places of concealment in the earth, or hustled away among the entangling and interlacing grasses. Looking about for the cause of all this excitement, the truth at once became painfully apparent. Three large, burly ants, representatives of _Formica subterranea_, a black species that is everywhere abundant in wooded regions, had intruded their obnoxious presence into the happy colony, bent, as it was evident, on pillage or slaughter.