INSECT VARIETY, 113 



of two insects, and that only the larger and stronger-winged 

 insects can produce it ; but M, I, B. Caprouier says, ' There 

 have hitherto been some doubts i£ the noise referred to was 

 peculiar to the male ; but M. Van Volxem, Avho has had frequent 

 opportunities of observing these insects enjoying their frolics, 

 affirms that the noise is common to both sexes/ We also learn 

 concerning these musical species, christened the ' Whip ■" but- 

 terflies, that they are common where their food-plants, JJales- 

 hamjna, abound; that they have a short, rapid flight, and 

 constantly alight on the trunks of trees ; and that four species^ 

 produce in flying a sound which has been compared by a good 

 observer to the rustling of a piece of parchment.'' " 



Mr. E. Doubleday says that " he had examined the butterfly 

 described by Mr. C. Darwin as making a noise, and that he 

 had detected a small membranous sac at the base of the fore- 

 wings, with a structure along the sub-costal nervure like an 

 Archimedean screw or diaphragm in the tracheae, especially at 

 the dilated base of the wing." Instigated by these observations, 

 I have myself examined the same butterfly, and find the superficies 

 of the wings that overlap are of considerable dimensions. On the 

 surface of the hind wing the costal vein (marked s, Fig. 1, Plate 

 lY.) is elevated, indurated, black, curved, and bare of scales for 

 about 3 '", and at first sight remarkably smooth and glossy. 

 But if this apparent smoothness be observed obliquely with a 

 strong magnifying power, in bright daylight, parallel indenta- 

 tions or slight stria? are seen all along its hinder surface, and 

 under the microscope these develop into a fine file or luua. When 

 the wings are expanded, this costal vein is received into a little 

 concavity in the inflated, rounded, smooth anal vein of the fore- 

 wing (marked I, Plate IV.) beneath and near its base, which 

 can be traced, after the fore-wing has been detached, by the 

 depression its great prominence leaves in the membrane adjacent. 

 This concavity seems suited in every way to act as a clasp, 

 sonorous when the wings are moved, while the whole adjust- 

 ment presents, in elementary form (if we overlook a slight 

 divergence as regards correspondence of the veins), the bristle 

 and catch that lock the wings of moths. 



* Feronia, Fornax, AmpJcinome, and Arethusa. 



