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Show 148 DR. E. BERGROTH ON STRIDULATING [May 16, patches are transversely strigose in the basal part, but the strife gradually become more oblique and are often practically longitudinal at the narrow end. From the position of the patches it is clear that the tibise cannot come in contact with them, and the active part of the stridulatory organ must be sought for elsewhere. I have found it on the inner side of the hind femur, where it consists of a number of very small spinous knobs arranged either in a single regular row or in two or three irregular ones. They are visible under a common pocket-lens, but under a compound microscope they present exactly the same structure as the tibial spinules of the Tetyraria. I propose to call them " spicula s t r id u la t o r ia The movements of the femur exactly correspond to the different direction of the strife of the ventral patches, these striae being always crossed at a right angle by the spicula." By rubbing the inner side of the femur over the ventral patch I have experimentally produced a stridulating noise. Stal seems to have observed the " spicula stridulatoria " in Platycoris and JYiarius, for in his above-quoted paper of 1867 he says they have the il femoribus posticis intus granulatis." In his larger work of 1876 he has omitted to mention it. In his revision of the Hemiptera Heteroptera of the British Museum, Distant was apparently not satisfied with the state in which he left the genus Dictyotus. He says* : " Dictyotus requires revision; all the species which Dallas included in his genus do not appear to be congeneric." Without having seen Dallas's types I had myself, in determining some species of this genus, come to the same conclusion. In some of his specific descriptions Dallas speaks of " a curved raised line on each side of the second and third segments" of the venter. Walker has also described his Mormidea detersa as having the " abdomen beneath with a short curved smooth line on each side near the base." I therefore suspected that these particular species belong to the genus Oncocoris, and this supposition has proved to be correct, my friend Mr. Distant having at my request kindly re-examined the types of the British authors previously referred by him to Dictyotus. It is therefore necessary to give a complete revised list of the species of Oncocoris, which follows here, and which is essentially founded upon the communications received from Mr. Distant. O n c o c o r is Mayr. Verh. zool.-bot. Ges. Wien, xvi. p. 362 (1866); Reise d. Novara, Hem. p. 44 (1866). Dictyotus Dali. List Hem. Brit. Mus. i. p. 139 (pro parte). Tarba Walk. Cat. Ilet. Hem. Brit. Mus. i. p. 236 (1867). 1. O n c o c o r is a p ic a l i s Dali. West Australia. Dictyotus apicalis Dali. List, i. p. 141 (1851). * Ann. & Mag. Nat. Hist. (7) v. p. 388 (1900). |