Similarly as, on the savannahs, I had observed a wasp attending the honey-glands of the bull's-horn acacia along with the ants; so at Santo Domingo another wasp, belonging to quite a different genus (_Nectarina_), attended some of the clusters of frog-hoppers, and for the possession of others a constant skirmishing was going on. The wasp stroked the young hoppers, and sipped up the honey when it was exuded, just like the ants. When an ant came up to a cluster of leaf-hoppers attended by a wasp, the latter would not attempt to grapple with its rival on the leaf, but would fly off and hover over the ant; then when its little foe was well exposed, it would dart at it and strike it to the ground. The action was so quick that I could not determine whether it struck with its fore-feet or its jaws; but I think it was with the feet. I often saw a wasp trying to clear a leaf from ants that were already in full possession of a cluster of leaf-hoppers. It would sometimes have to strike three or four times at an ant before it made it quit its hold and fall. At other times one ant after the other would be struck off with great celerity and ease, and I fancied that some wasps were much cleverer than others. In those cases where it succeeded in clearing the leaf, it was never left long in peace; for fresh relays of ants were continually arriving, and generally tired the wasp out. It would never wait for an ant to get near it, doubtless knowing well that if its little rival once fastened on its leg, it would be a difficult matter to get rid of it again. If a wasp first obtained possession, it was able to keep it; for the first ants that came up were only pioneers, and by knocking these off, it prevented them from returning and scenting the trail to communicate the intelligence to others. Dr. Erasmus Darwin records an observation ('Zoonomia,' i., p. 183) which, from having since been so widely quoted, deserves to be called classical. He saw a wasp upon the ground endeavouring to remove a large fly which was too heavy for it to carry off. The wasp cut off the head and abdomen, and flew away with the thorax alone. The wind, however, catching the wings of this portion made it still too unwieldy for the wasp to guide. It therefore again alighted, and nipped off first one wing and then the other, when it was able to fly off with its booty without further difficulty. This observation has since been amply confirmed. I shall quote some of the confirmatory cases. Mr. R. S. Newall, F.R.S., in _Nature_, vol. xxi., p. 494, says:--