Mr. J. O. Westwood's Memoirs, ^c. 123 XXIV. Memoirs on various Species of Hymenopterous Insects. By J. O. Westwood, F.L.S., &c. [Read 4th February and 3rd June, 1839.] I. On the Economy) and Relations of the Genus Xiphydria. [The various situations in which the genus Xiphydria was arranged in the classifications of Latreille, Jurine and Leach, together with its intimate relation with the genus Sirex, Linn., and consequent importance in the distribution of the Hymenoptera given by Mr. MacLeay in the " Horae Entomologicse," (in which the Tenthredi-nidce are removed from the rest and united with the Trichoptera, and (Sirex is made an osculant suborder under the name o{ Bom-hoptera,^ induced me, about twenty years ago, minutely to examine the structure of the ovipositor and sting of the chief groups of the Linnaean Hymenoptera, as well as the preparatory stages of such species as presented themselves. And although the general results of these inquiries have been given to the Entomologist in my " In-troduction to the Modern Classification of Insects," a considerable number of details and sketches still remain unpublished. The discovery by Mr. Cooper of the preparatory stages of the genus Xip)hydria afforded a very important clue to the solution of the question of the relations of that genus, and I accordingly drew up an extended memoir, (noticed in the ZoologicalJournal for 1827,) in which the entire structure of the genus, in its perfect and prepa-ratory states, was reviewed with reference to that of the adjacent groups, and in which the position of the genus was traced, through the writings of preceding authors, and the formation of the ovi-positor throughout the Hymenoptera especially examined ; the propriety of the general arrangements of the order investi-gated ; the situation of the present genus therein discussed, and a plan of distribution of the order proposed. During the last eighteen years, however, the philosophical investigation of the order has made such rapid strides that much of what I had written is now rendered useless ; I have therefore struck it out of my memoir, which is here confined to the details of the structure of the insect in its different states, and a comparison thereof with the allied genera.— /. 0. W. 1845.] By the kindness of my friend, Abraham Cooper, Esq., R.A., I am enabled to present my readers with a description of the larva of a species of the Hymenopterous genus Xiphydria, which will,
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