2 r 4 The Scottish Naturalist. 



The editors remark : — "It will be remembered that last year (see E. M. M. 

 vol. vii. p. 231.) Mr. Swinton asserted his belief that H. prasinana produced an 

 audible noise. This year he has followed up the enquiry and very kindly sent 

 us living specimens of H. prasinana (as did also Mr. Hellins), which he believed 

 to have heard produce a sound. We were not fortunate enough to detect it 

 ourselves. There is much that is singular in the formation of the parts of the 

 body intermediate between the thorax and abdomen in the genus Halias 

 [Hylophila], and we are willing to accept Mr. Swinton's testimony that they 

 are connected with sound-producing powers. In answer to our query as to 

 whether the frenum or spur of the hind-wing might not be connected with the 

 sound, Mr. Swinton informs us that, according to experiments he made, the 

 spur has nothing to do with it." 



On the evening of 28th May, when mothing in the oak-wood surrounding my 

 house, I noticed what I thought was a beetle, flying round a small oak, and 

 giving vent all the time to a sharp, quick sound, very similar to that produced 

 by the Longicorn beetle Astinomus when held betwen the fingers. Though I 

 failed to catch this individual, I was more successful with another which was 

 behaving in the same manner. When in the net the sound ceased, and I saw 

 to my astonishment that the insect was a moth. It then occurred to me that 

 Hylophila prasinana was said to produce a sound, and on examining my 

 captive I was therefore not surprised, though much pleased, to find that it 

 belonged to this species. 



The following morning I tried some experiments with my captive, moving 

 his wings and making him fly, but was not able to elicit any sound from him. 

 I conclude, therefore, that the noise is not produced by the mere mechanical 

 action of the wings, but is dependent on the will of the animal. I then killed 

 the creature, which was a male, and dissected him. On removing the patagia 

 and hairs from the thorax, several small projecting horny plates, both frontal 

 and lateral, were apparent, but I could not discover that the wings produced 

 any sound in connection with them. 



I then directed my attention to the structures between the thorax and hind- 

 body and from them I believe the sound proceeds. On examining the under- 

 side of the animal, a large semi-lunar opening immediately behind the meta- 

 sternum will be perceived. On dissection this opening will be found to commu- 

 nicate with a large membranous plate, not flat, but folded at its posterior and 

 inferior edge, and elevated and depressed in other parts, and somewhat semi- 

 lunar in outline. To this plate numerous strong muscles are attached, and by 

 action of these muscles on the plate, I think the insect produces the noise in 

 question. This sound-producing structure (if such indeed be its function) is 

 analogous to the ' ' drum" of the male Cicada, and occupies a similar position. 



The same evening I again went out to the wood and captured another speci- 

 men of the Hylophila in the act of "squeaking." The sound was quite distinct 

 at a distance of ten feet or more. Next morning I treated him (it was a male) in 

 the same manner as I had the first specimen, and with a similar result. I found 

 that a good imitation of the sound may be made by rubbing the point of a 

 knitting-needle on the closed blade of a clasp-knife. I have since taken another 

 specimen (also a male) flying round an oak, but not producing any noise. ' 



Several other moths are known to produce sounds, but apparently the noise 

 is caused in a different manner in each of the sound-producing genera. The 

 most celebrated of these sound-producing moths is, of course, Acherontia atro- 

 pos, but the modus operandi in this species seems still not to be clearly under- 



