Exhibitions. 



Bare British Beetle. — Mr. Bedwell exhibited a specimen 

 -of the beetle OtiorrhyncJms ligustici, L., taken near Ventnor, 

 one of the rarest of the British weevils, of which there has been 

 no recent record. 



Fluorescence in Lepidoptera. — Drs. J. C. Mottram, 

 F.Z.S., and E. A. Cockayne, D.M., F.R.C.P., gave a demon- 

 stration of fluorescence in Lepidoptera by ultra-violet radia- 

 tion, of which they have submitted the following account. 

 The demonstration has only recently become possible as a 

 result of an invention of Prof. Wood of Baltimore University. 

 Prof. Wood has produced a glass which, whilst allowing 

 ultra-violet radiation to pass, is opaque to light. It is trans- 

 parent to radiation of wave-lengths lying between 3900 and 

 3100 A.V. It also allows a narrow band of red light to pass ; 

 this can, however, be avoided by using a, quartz mercury 

 vapour lamp, which is deficient in this light. Used in this way 

 a beam of invisible ultra-violet radiation is obtained. A similar 

 glass is now being made in this country by Messrs. Chance Bros. 



This radiation is especially useful for the examination of 

 objects for fluorescence, so much so that a great many objects 

 not hitherto known to be fluorescent were found to be so. 

 It would seem to be a delicate test because a great contrast 

 is produced between non-fluorescent objects, which appear 

 black no matter what their local coloration, and fluorescent 

 objects which glow more or less brightly. 



In view of the interest which physicists have taken in the 

 brilliant coloration of many birds and insects in an endeavour 

 to explain them on a physical basis,* it occurred to us that an 

 examination in ultra-violet radiation would go far to decide 

 whether or no fluorescence played any part in these brilliant 

 colours. The first insects examined were various Lycaenidae and 

 other irridescent species, chiefly on account of the paper by Sims,t 

 suggesting that their colour is due to a fluorescent pigment. 



We chose a number of representative British and Tropical 



Lycaenidae, including Agriades coridon and A. thetis, and a 



MorpJio, as examples of irridescent blues. Purples and 



* Lord Rayleigh, Philos. Mag.. 6tli Series, No. 217. 

 t H. M. Sims, Canadian Entomologist, 1915, p. 161. 



