igoi] ENTOMOLOGICAL NEWS. 279 



On the Stridulation of Passalus Cornutus Fabr. 

 By George F. Babb, A.M., Amherst, Mass. 



During the fall of 1900, a large number oi Passalus cornutus 

 Fabr. were taken from decaying apple, oak, chestnut and elm 

 logs in the vicinity of Amherst. These beetles, when dis- 

 turbed, all made a peculiar hissing noise which at once at- 

 tracted attention. 



Riley states, in describing this insect, that "a sufficient!}^ 

 careful examination will end in the knowledge that it is caused 

 b}'^ the rubbing of the pygidium against the inside of the wing- 

 covers" (Mo. Rep. iv, p. 139, 1872). 



Le Conte remarks that '' Passalus cornutus makes a loud stri- 

 dulation by rubbing the acute edge of the ventral .segments 

 against the inner edge of the elytra" (Psyche ii, p. 126, 1878); 

 and Ohaus goes to great length in a description of the abdomi- 

 nal pleurites and of the inner edges of the wing-covers as the 

 factors in the production of the sound (Stett. Ent. Zeit. 61, p. 

 164, 1900). 



Packard, in his article on "Sounds of Insects" (Text-book 

 of Entomology), makes no mention whatever of Passalus 

 cornutus. 



Sharp states that ' ' the adult insect has no sound-producing 

 organs," and emphasizes the statement by contrasting the 

 adults with the larvae (Camb. Nat. Hist, vi, p. 192, 1899). 



Prompted by this conflict of authorities the writer carried on 

 at the Entomological Laboratory of the Massachusetts Agricul- 

 tural College a series of carefully conducted experiments under 

 the direction of Dr. H. T. Fernald. The results obtained do 

 not agree with those quoted above. 



It is not surprising that L,e Conte was mistaken, for on the 

 pleurites of the segments of the abdomen are plates covered 

 with bristles directed upward and on the corresponding por- 

 tions of the elytra are bristles directed downward as described 

 by Ohaus. The interference of the bristles might naturally be 

 thought to produce the hissing sound so peculiar to Passalus 

 cornuttis. This impression would be strengthend by the fact 

 that every time that the intermittent sound is heard the insect 

 moves its abdomen upward into the cavity formed by the elytra. 



