450 BRITISH LEPIDOPTERA. 



long as one presses out the air, the sound, however, ceasing 

 as soon as one cuts off the tongue or separates its two 

 parts. It may be stated that H. Redlich, in his interesting 

 investigation of this phenomenon (Ent. Zeit. Guben, iii., pp. 130-131 

 1890), has, by experiment, established that the part of the proboscis 

 outside the mouth has no share in the production of the noise. 

 Maillard says {Tijds. v. Ent..^ 1862, p. 20) that an incision made 

 between the eyes of a living moth discloses a cavity (formed by the 

 expansion of the food-canal), which occupies the greater part of the 

 head-space, and that widens and contracts, whilst the insertion 

 of the tongue forms the crop into an upturned flap which is set in 

 vibration by the in-passing and out-passing air. Moseley confirms* 

 {Nature, vi., pp. 151-153), in an excellent paper, the theory of Passerini, 

 and gives a diagram and description of the head-cavity and its muscles. 

 Chapman, quite independently of Moseley's experiments, came to 

 the same conclusion as to the source of the sound (see Ent. 

 Rec, vol. xiii., p. 127). He writes: "Material being available I 

 thought it well to investigate the subject for myself. The specimens, 

 having come by post, did not cry so freely as might be desired, 

 and gave an undue importance to anatomy over experiment. 

 It was plain that the noise appeared to come from, or from near, 

 the head ; the friction of proboscis and palpi had nothing to do 

 with it, as they could be held apart without affecting it. The 

 only movement associated with the noise was one of the under- 

 sarface of the base of the abdomen ; a similar movement, as an 

 ordinary respiratory one, occurred without any noise being 

 produced. I made search, however, amongst the air-sacs and 

 dilated tracheae of the thorax and abdomen without finding any- 

 thing to produce a sound. I then examined the spiracles which 

 have a very beautiful double valve of lacelike structure as an 

 outward protection, but could find nothing to suggest the 

 prothoracic spiracle as a squeaking organ, nor could I find 

 anywhere a stridulating surface. The corrugations of the 

 proboscis' and palpi are rounded, and do not touch each other, 

 confirming the experimental proof that there is no strid illation 

 here. A strained extension of the proboscis did not stop the 

 sound, but distinctly altered the note, rendering it certain 

 that the source of the sound was affected by the altered position. 

 The opposed edges of the two halves of the proboscis are 

 firmly held together, and no friction here causes the sound. In 

 the interior of the head, facing the lumen of the proboscis, is 

 an opening, capable of varying its form from nearly circular to 

 a narrow slit ; this opens behind into a cavity of a diameter 

 of about 2mm., lying immediately behind the clypeal region. 

 This cavity has walls of fairly fixed position, being conditioned, 

 below and laterally, by the surrounding chitinous structures of the 

 head, but above it is not in contact with the walls of the 



into which it simply opens near the base of the trunk. We may further note here 

 Passerini's experiment in which the abdomen was separated from the thorax, the 

 moth continuing to squeak, in spite of the mutilation. 



*This author gives by fai the best account of the real cause of the sound that 

 has been published. We were unfortunate in not being able to refer to it until our 

 own summary had been completed. 



