CLAVICOENIA AND LAMELLICORNIA. 



55 



figured. It consists of a narrow longitudinal elevation upon tlie posterior part 

 of the head, lying partly within the cavity of the prothorax. This ridge is 

 divided transversely into a large number of microscopic ridges, which by in- 

 and-out movements of the head scrape a sharp corresponding ridge inside 

 the cavity and so set up vibrations, no doubt of a more or less musical character, 

 although in so small an insect they may not be easily audible to the human ear. 



I have described an apparatus essentially similar in other genera of 

 Ekotylidae, but in all of these there are two files, one on each side of the head. 

 Usually they are rather widely separated. In the typical species of the genus 

 Thallis (T. compta and T. vinula of Erichson) the apparatus is absent. In a 

 third species, T. janthina, associated with them by Erichson, two converging 

 but well separated files are present, and in T. insueta Crotch, the two files are 

 close together. These and other species allied to them will no doubt ultimately 

 be formed into new genera. 



47. Monothallis samoensis Heller (Text-fig. 8). 



Thallis samoensis, Heller, Arch.f. Naturg., Vol. 

 Ixxxiv, 1918, p. 61, 1920. 



Muhfanua, Nov. 

 Loyalty Is., New 



Upolu 1. : Apia, Oct 



Fiji Is. (Jepson), 

 Hebrides (Aneitynm). 



This is an abundant insect, which hves 

 and feeds upon woody tree-fungi, specimens 

 having been bred out of one of these in the 

 Botanical Department of the British Museum 

 so long ago as 1859. According to Dr. Heller, 

 it is found also in New Pomerania in the 

 Bismarck Archipelago. 



Text-fig. 8. — Monothallis 

 samoensis Heller. 



48. Euxestus basalis Motsch. 



Tritomidea basalts Motsch., Etudes Ent., Vol. viii, p. 106, 1859. 

 Upolu I. : Apia, Dec. to Feb. 



Tutuila I. : Pago Pago, Sept. (Swezey and Wilder). 



