These stridulating organs were mentioned by C. Darwin as probable examples of the action of sexual selection; they are, however, frequently present in both sexes, and in some families also in the larvae.
In a large number of beetles of different families, stridulating areas occur on various segments of the abdomen, and are scraped by the elytra.
Stridulating organs among beetle-larvae have been noted, especially in the wood-feeding grub of the stag-beetles (Lucanidae) and their allies the Passalidae, and in the dung-eating grubs of the dor-beetles (Geotrupes), which belong to the chafer family (Scarabaeidae).
Whatever may be the true explanation of stridulating organs in adult beetles, sexual selection can have had nothing to do with the presence of these highly-developed larval structures.
The root-feeding larvae of the cockchafer and allied members of the Scarabaeidae have a ridged area on the mandible, which is scraped by teeth on the maxillae, apparently forming a stridulating organ.
The function of the stridulating organs just described is presumably to afford means of recognition by sound.
France, 1886); and stridulating organs by C. J.
In many of those ants whose third abdominal segment forms a second " node," the basal dorsal region of the fourth segment is traversed by a large number of very fine transverse striations; over these the sharp hinder edge of the third segment can be scraped to and fro, and the result is a stridulating organ which gives rise to a note of very high pitch.
Lastly, the males of some species of spiders differ from the females in possessing stridulating organs consisting of horny ridges and spikes and lodged either between the mandible and palpus as in some species allied to Linyphia, one of the Argyopidae, or between the cephalo-thorax and abdomen as in Steatoda, one of the Theridiidae and Cambridgea, one of the Agalenidae.
So far as is known, however, only the large spiders belonging to this group possess this special means of defence, and in many other species this is accompanied by highly-developed stridulating organs resembling those of rattlesnakes and scorpions in function.
The Hemiptera are remarkable for the variety of their stridulating organs.
Idem, " Stridulating Organs of Spiders," Ann.