The Monedula is an adroit fly-catcher, for though it kills numbers of fire-flies and other insects, flies are always preferred, possibly because they are so little encumbered with wings, and are also more easily devoured. It occasionally captures insects on the wing, but the more usual method is to pounce down on its prey when it is at rest. At one time, before I had learnt their habits, I used frequently to be startled by two or three or more of these wasps rushing towards my face, and continuing hovering before it, loudly buzzing, attending me in my walks about the fields. The reason of this curious proceeding is that the Monedula preys largely on stinging flies, having learnt from experience that the stinging fly will generally neglect its own safety when it has once fastened on a good spot to draw blood from. When a man or horse stands perfectly motionless the wasps take no notice, but the moment any movement is made of hand, tail, or stamping hoof, they rush to the rescue, expecting to find a stinging fly. On the other hand, the horse has learnt to know and value this fly-scourge, and will stand very quietly with half a dozen loud Avasps hovering in an alarming manner close to his head, well knowing that every fly that settles on him will be instantly snatched away, and that the boisterous Monedula is a better protection even than the tail--which, by the way, the horse wears very long in Buenos Ayres. I have, in conclusion, to relate an incident I onco witnessed, and which does not show the Monedula in a very amiable light. I was leaning over a gate watching one of these wasps feeding on a sunflower. A small leaf-cutting bee was hurrying about with its shrill busy hum in the vicinity, and in due time came to the sunflower and settled on it. The Monedula became irritated, possibly at the shrill voice and bustling manner of its neighbour, and, after watching it for a few moments on the flower, deliberately rushed at and drove it off. The leaf-cutter quickly returned, however--for bees are always extremely averse to leaving a flower unexplored--but was again driven away with threats and demonstrations on the part of the Monedula. The little thing went off and sunned itself on a leaf for a time, then returned to the flower, only to be instantly ejected again. Other attempts were made, but the big wasp now kept a jealous watch on its neighbour's movements, and would not allow it to come within several inches of the flower without throwing itself into a threatening attitude. The defeated bee retired to sun itself once more, apparently determined to wait for the big tyrant to go away; but the other seemed to know what was wanted, and spitefully made up its mind to stay where it was. The leaf-cutter then gave up the contest. Suddenly rising up into the air, it hovered, hawk-like, above the Monedula for a moment, then pounced down on its back, and clung there, furiously biting, until its animosity was thoroughly appeased;