404 Mr. G. A. K. Marshall on 



stethoscope (foi- both ears) with the usual form of end-piece 

 replaced by a cork traversed by a glass tid)e about one- 

 eighth of an inch in intt'rnal diameter, and with its terminal 

 lip very slightly expanded into a small funnel. If, while 

 the ear-pieces arc inserted in both ears, the open end be 

 moved about near to a stridulating insect, an extraordinary 

 reinforcement of sound takes place as the source is 

 approached, so great indeed that I found no difficulty in 

 localizing it within a small area. Excessively minute 

 sounds become clearly audible by the use of this valuable 

 and simple piece of apparatus. If there be good reason to 

 suppose that the stridulation of any insect is inaudible to us, 

 viz. if the structure of its organ and the movements set up 

 as a result of irritation suggest stridulation, it would be 

 feasible, I believe, to transmit the vibrations to some re- 

 cording surface other than the tympanum of the human 

 ear, and thus to investigate them. 



It is usually possible to distinguish readily between the 

 sounds which are emitted in courtship and those which are 

 produced on irritation and are probably of a warning or 

 terrifying significance, inasmuch as they arise from quite 

 different stimuli and tend to be accompanied by character- 

 istic movements or attitudes. This latter association is 

 exhibited by the imago of Aclicrontia atropos, and the snap- 

 ping sound made by its larva, due to the movements of the 

 mandibles, is also of terrifying significance. I have once heard 

 the epigamic sound of TLtlias prasinana, but only when 

 the male was pursuing the female and the whole mode of 

 flight was subordinated to the ends of courtsliip. Generally 

 speaking, any sound produced by both sexes on irritation 

 or attack, and accompanied by threatening attitudes or 

 movements (as of the mandibles), or merely violent strug- 

 gles, is to be interpreted, with a high degree of probability, 

 as a warning or intimidating character. The decision 

 between warning and intimidation can only be arrived at 

 after an experimental investigation into the qualities of 

 each separate species. 



Pseudaposematic sounds are also well known in birds, 

 especially those which build in holes in trees and hiss like 

 a snake when disturbed. Many lizards also hiss when 

 extremely irritated. Professor J. W. Gregory, F.R.S., 

 describes a grasshopper at Kurawa which hissed so that 

 he at first mistook it for a snake ("The Great Rift Valley," 

 London, iSlXi, p. 27;}).— E. 15. P.J 



