148 DR. E. BERGROTH ON STRIDULATING [May 16, 
patches are transversely strigose in the basal part, but the striz 
gradually become more oblique and are often practically longi- 
tudinal at the narrow end. From the position of the patches it 
is clear that the tibize cannot come in contact with them, and the 
active part of the stridulatory organ must be sought for elsewhere. 
{ 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 
stridulatoria.” The movements of the femur exactly correspond 
to the different direction of the striz of the ventral patches, these 
strie 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 Niarius, 
for in his above-quoted paper of 1867 he says they have the 
“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 
T had myself, in deterrnining 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. 
Oncocoris Mayr. 
Verh. zool.-bot. Ges. Wien, xvi. p. 362 (1866); Reise d. 
Novara, Hem. p. 44 (1866). 
Dictyotus Dall. List Hem. Brit. Mus. i. p. 139 (pro parte). 
Tarba Walk. Cat. Het. Hem. Brit. Mus. i. p. 236 (1867). 
1, ONcocorRIs APICALIS Dall. West Australia. 
Dictyotus wpicalis Dall. List, i. p. 141 (1851). 
* Aun. & Mag. Nat. Hist. (7) v. p. 388 (1900). 
