448 BRITISH LEPIDOPTERA. 



seems to have a notch or incision opposite the first segmental 

 incision ■ the inner side of the membrane — that which is turned 

 towards the cleft — is quite naked, the outer side or surface, with 

 the exception only of a part of the margin, being clothed with the 

 fur which covers the entire body of the moth ; the inner hollow 

 of the cleft is clothed, as part of the general surface of the body, 

 with an extremely fine, white, naked, and elastic skin, and functions, 

 on the passage of the air out of the spiracle, as a resonating body 

 when the vibrations of the tympanum are communicated thereto. 

 When the moth is not disturbed, and respiration is going on 

 normally, there is a large tuft of long yellow hairs lying close 

 beside one another in the cleft covered by the tympanum, but, 

 when it is excited, the more violent passage of the air from the 

 spiracle, and the muscles of the abdominal segments extending the 

 cleft, cause the hairs to become erected, and they now form — bristling 

 and trembling on account of the stream of air which is passing 

 out — two funnel-shaped tufts projecting far beyond the upper 

 surface of the segment. At the same time, the tympanum, which 

 is also extended, begins to vibrate and the shrill cry is produced." 

 He concludes that the vocal apparatus of M. atropos is, therefore, 

 near that of Tettigonia, and nothing so unique as had hitherto been 

 supposed. We have quoted this in full as characteristic of the 

 details given by those observers who have mistaken the $ 

 abdominal tufts for the sound-producing apparatus. Johnson 

 asserts (Ent., ii., p. 325) that the imago of M. atropos makes its 

 noise " by respiration through an aperture under the superior wing, 

 &c," i.e., through the cavity in which the $ tufts lie. This state- 

 ment was contradicted by Taylor (loc. cit., iii., p. 3) who pointed 

 out that the 2 squeaks as loudly as the $ , although she has 

 no such apertures. He himself thinks that " the sound is caused 

 by the forcible passage of air through the spiracles." Burmeister 

 hesitates to accept (Handbuch der Ento/n., i., p. 514) Passerini's 

 conclusions, unless there is a vibrating membrane at the entrance 

 where the air was supposed to leave the head, but adds that 

 Duponchel has stated that a fine membrane exists between the eyes 

 and base of the tongue which might be set in vibration by the 

 ingoing and outgoing air ; at the same time, Burmeister believed 

 that the sound originated in the head. Russell states (Ent. 

 Rec, xii., p. 345) that the noise appeared to him to be 

 produced by a movement of the joints or some of the joints of 

 the legs. Preston believes (Ent., iii., p. 4) that the sound is 

 caused by the movement of a very strong muscle and states 

 that he was able to produce the sound artificially by moving 

 the same. Newman also states (loc. cil.) that this is his opinion 

 of its origin. Sandlin observes (E/it., xxiv., p. 297) that he 

 heard the sound when he moved the thorax of a specimen that 

 he was setting. Anderson reverts to Reaumur's idea, and has no 

 doubt (Ent., xix., p. 249) that the sound is caused by the pro- 

 boscis rubbing against the palpi, though he believes that the 

 friction of some parts of the thorax may have somewhat to do 

 with it, although, as soon as the proboscis is held down, the squeaking 

 ceases. Paris, who states that the cry of the imago is like that 

 made by the larva, but lighter and sharper, describes (Bull. Soc. Ent 



