Feb. I, 1877] 



NATURE 



293 



suddenly, elevates its head, and remains motionless in a listening 

 attitude ; after pausing thus for a few seconds, it again runs to 

 about the same distance as before, again stops to listen, and so 

 on. These successive excursions are usually made in the same 

 direction ; but every now and then, during the process of listen- 

 ing, the thrush apparently hears a sound proceeding from some 

 point within the circle which it has last entered ; immediately 

 the course of progression is deflected at an angle from the con- 

 tinuous straight line in which all the previous excursions were 

 made, and, either with a single rush or after one or two brief 

 pauses to make quite sure of the exact spot, the bird may nearly 

 always be seen to find a worm. 



I may take this opportunity of thanking your various corre- 

 spondents for the information which they have supplied with 

 regard to the towering of birds. Some of the letters men- 

 tion ducks, teals, and widgeons as birds which occasionally 

 tower. May I ask the writers of these letters whether the action 

 in these cases resembled that of true towering in the case of par- 

 tridges and grouse ? I ask this because one of the'numerous 

 letters by which my communication to Nature has been 

 ansv/ered in the Field, states that birds of this build never tower ; 

 and on this supposed fact the writer constructs a theory as to the 

 mechanism of towering in general. All the correspondence taken 

 together cannot leave any doubt that there are at least two kinds 

 of towering : — viz. (i) The common kind which I described, 

 and the cause of which is certainly pulmonary hemorrhage ; and 

 (2) a very rare kind which I have never myself witnessed, 

 and the immediate cause of which appears to be cerebral injury. 

 In the case of the second, or rare kind of towering, all the cor- 

 respondents are agreed that the bird is not dead when found, and 

 that it may even fly away again when disturbed. Never having 

 had an opportunity of observing such a case, of course any hypo- 

 thesis by which I may try to explain the cause of the rare kind of 

 towering is of no further value than a conjecture ; but I may 

 remark that both kinds of towering may possibly be due to the 

 same cause, if the parts of the brain which are injured when the 

 second kind of towering ensues, are the parts whose injury 

 Brown-Sequard found to be attended in the case of mammals, 

 with bleedmg of the lungs. At any rate, it would be worth while 

 for any sportsman who may have the opportunity, to dissect a 

 bird which he has seen to exhibit the second kind of towering, 

 in order to ascertain whether, in such cases also, some degree of 

 pulmonary haemorrhage may not have taken place. 



George J. Romanes 



In Mr. G. J. Romanes' interesting remarks (Nature, vol. 

 XV., p. 177) on the sense of hearing in insects, he says : — 

 "In the case of moths, however, I believe that sounds are never 

 emitted, except of course the Death's-head." 



As I trust that insects will continue to have a place in his ob- 

 servations, may I be allowed to call Mr. Romanes' attention to 

 the following species of Lepidoptera which are known to pro- 

 duce sounds : — 



I. Vanessa, several species. — The sound produced — which 

 has been compared to the friction of sand-paper — has been 

 noticed by several observers, viz.. Rev. J. Greene {Proc. Ent, Soc. 

 of London, New Series, ii., p. xcviii.), Mr. Hewitson {I.e. iv., 

 p. ii.), and Mr. A. H. Swinton {Entomologists' Monthly Maga- 

 zine, xiii,, p. 169, January, 1877), who describes the apparatus 

 by which the noise is produced. On tRe under surface of the 

 upper wing one of the nervures is roughened like a file, and 

 upon this a raised nervure on the upper surface of the under- 

 wing plays ; there is also a circular embossed patch of the wing- 

 membrane destitute of scales, which Mr. Swinton thinks serves 

 to "impress the musical tremours." The object of this stridu- 

 lation, Mr. Swinton suggests, may be classed with those pheno- 

 mena of rivalry and love so conspicuous in the Orthoptera, &c., 

 but at the same time it is produced when the insects are dis- 

 turbed, and possibly also when the sexes are coquetting in mid- 

 air. Moreover, the development of the mechanism is greatest 

 in the female, contrary to the usual rule. For my own part, I 

 incline to think that the object of the sound is rather the intimi- 

 dation of possible enemies than a sexual love-call. Both Mr. 

 Greene's and Mr. Hewitson's cases occurred when insects that 

 were hibernating were disturbed, and the sound was renewed 

 whenever the disturbance was repeated. These butterflies hiber- 

 nate in dark holes and corners, and the sound may be intended 

 to suggest to the disturber the hiss of a snake or the note of an 

 angry wasp or bee. As the perpetuation of the species depends 

 for the most part on the female, she is provided with a stronger 



apparatus. If the sound is produced when the sexes are coquet- 

 ting, it may be the butterfly expression of a playful " Get along 

 with you." 



2. The well-known case oi Acherontia (the "Death's-head 

 Moth "). — The sound here also is probably for intimidation, and 

 not a love-call. I cannot at present call to mind any observations 

 on any disparity of the sound in the sexes. 



3. Setina, several species, and 



4. Chelonia pudica. 



The sound emitted by these insects — which is compared to 

 the ticking of a watch — is described by M. A. Guenee {Ann. 

 Soc. Ent. Fr., 4"^ ser., vol. iv. 1864; translated in Ent. Month. 

 Mag., i. 223) who says that it is produced by two tympaniform 

 vesicles situated in the pectoral region, and is much more deve- 

 loped in the male than in the female. This, M. Guenee re- 

 marks, is rather curious, for, as the females of Setina can scarcely 

 fly, it would seem that, if the organ of sound is to produce a love 

 call, it is the female, and not the male that should have it most 

 strongly developed. M. Guenee consequently expresses himself 

 unable to give any plausible reason to account for the object of 

 the sound. 



A reason has occurred to me and I here give it for what it 

 may be worth. We know that the females of several Lepi- 

 doptera (especially wingless females) have the power of emitting 

 a scent which attracts the males, often from considerable dis- 

 tances. When the male of Setina is hunting for the female and 

 making probably his drums vibrate loudly, the sound reaching 

 the concealed female may excite her to give out an increased 

 odour, and thereby more surely attract the male. In short the 

 drums are organs of excitation. 



5. Hylophila prasinana. — This species Mr. Swinton {Entom. 

 Monthly Mag., vii. 231) has noticed to emit a twittering sound, 

 which he thinks is produced by a structure between the thorax 

 and abdornen. 



I have been fortunate enough to have also had an opportunity 

 of hearing the sound produced by this species {Scottish Naturalist, 

 i, 213). The sound resembles a continuous squeaking and was 

 heard on more than one occasion, and was audible at a distance 

 of ten feet or upwards. All the specimens that I caught in the 

 act of squeaking were males, so that I cannot say whether the 

 other sex squeaks or not. The sound is emitted whilst the insect 

 flies about the bushes, and the object of it is probably the same 

 as I have suggested above in the case of Setina. The emission 

 of the sound is quite voluntary on the part of the moth, as speci- 

 mens taken in the act of squeaking and made to fly afterwards 

 did not then give out any sound. Careful dissection revealed no 

 structure that appeared capable of producing the noise except a 

 tympaniform plate situated at the base of the hind body. 



6. H. quercana. — According to Mr. Swinton {I.e., viii. 70) 

 this species can make a "membranous sound," which he thinks 

 is produced by the wing catching a little horny lateral thoracic 

 plate. 



There may be other recorded instances of sound-produciiag 

 Lepidoptera, but I cannot at present recall any to mind. It is 

 probable moreover that more species than are generally supposed 

 emit some kind of a sound. It is therefore much to be regretted 

 that the many collectors of Lepidoptera — whose sole aim seems 

 to be the amassing of large collections and whose lack of any- 

 thing beyond the mere desire to accumulate specimens, has made 

 entomology a bye-word amongst the sciences— would not spend 

 some of their misplaced energy in really studying the objects of 

 their attention. 



Mr. Romanes' observation of the sensible appreciation moths 

 have for high-pitched notes suggests a question. Does the shrill 

 squeaking of bats convey an intimation to moths of the approach 

 of one of their greatest enemies ? 



It is to be noted moreover that in the majority of cases the 

 sounds emitted by moths, and indeed all insects, themselves, are 

 high pitched. F. Buchanan White 



Perth, January 12 



P. S.— Since the above was written I see that my friend Mr. 

 McLachlan has pointed out (Nature, vol. xv, p. 254) another 

 record of a sound-producing moth — Euprepia matronula. 



The perusal of Mr. McLachlan's letter on " Sense of Hearing 

 &c., in Birds and Insects" has recalled to my memory another 

 instance of a Lepidopterous insect which possesses the property 

 of emitting a marked sound when on the wing. This is a 

 common Brazilian butterfly {Ageronia feronia), and attention 



