Mr. F. Smith exhibited an ichneumon, Rhyssa persuasoria, placed in his hands by Mr. Bond, which appeared to have worked its long ovipositor, bradawl-fashion, through a piece of fir-wood, in quest of the larva of Sirex juvencus, on which it is parasitic; part of the ovipositor had been left in the wood. Mr. Bond had some years ago found at Bournemouth two ichneumons with their ovipositors so firmly fixed into wood that he was unable to remove them. Mr. Smith had always hitherto supposed that the Rhyssa inserted its ovipositor into the holes made by the Sirex, instead of making a hole for itself in the tree: if the latter were the rule, how did the ichneumon detect the presence of the larva within the wood, and know where to insert its ovipositor? Mr. Edward Doubleday, however, had told him that he had seen twenty or thirty specimens of the female of a Pelecinus which had perished with their elongated abdomens inserted into the stem of a tree, whence they had been powerless to extract them; the male had a clavate abdomen, but that sex had never been met with by Mr. Doubleday.

    Mr. Bates inquired whether an ovipositor was not, homologically, a modification of one of the abdominal segments.

    Mr. Smith thought it was rather a modification of the aculeus.

    Mr. Wallace suggested the converse, namely, that the sting was a modified ovipositor, and that its use as a weapon of defence was a secondary and acquired use.