The biology of Rhyssa persuasoria, L., and of Ibalia leucospoides, Hochenw., has already been sketched in a preliminary paper published in this Bulletin (xix, pp. 67–77, pl. iii, 1928) in collaboration with Mr. R. N. Chrystal, of the Imperial Forestry Institute. The following observations were made by the writer chiefly at the Farnham House Laboratory, during the spring and summer of 1928, and are gathered together in view of his departure from England. The work of collecting and rearing supplies of Rhyssa and Ibalia for shipment to New Zealand, for the biological control of Sirex nodilio (juvencus), has been continued on a larger scale. The present notes were made incidentally during this work and are arranged under nearly the same headings as in the previous paper, to which they are supplementary. One error needs correcting. It was stated (on p. 75) that the larch (Larix europaea, D.C.) is indigenous, though actually planted in the Oxford locality mentioned. As a matter of fact, of course, larch, though Palaearctic, is not indigenous to Britain.