Lijcaenidae. — Curetis acuta, Cyaniris argiolus, L. (undersides 

 slightly fluorescent). 



The most- brilliant are EucfenumjJtenjx, Ourapteryx and 

 Sirinopteryx. The closely allied Thino2Jteryx does not fluoresce. 

 Aspilates strigillaria, Hb., is non-fluorescent, though A. gilvaria 

 is one of the brightest in ultra-violet radiation. 



Abraxas, which is closely allied to Vindusara in structure 

 and resembles it in colour and markings, shows no fluorescence, 

 nor does the white Uraniid Micronia aculeata, Guen. It will 

 be interesting to examine genera allied to those which we have 

 found to be fluorescent. In the case of the Geometridae 

 Mr. Prout has promised to help us. All the species, which 

 we have discovered to be fluorescent so far are whitish or 

 yellow, but whether it is due to the same pigment in the 

 difierent groups we are unable to state. 



By carefully denuding an area of wing of its scales on both 

 the upper and under sides we found that the membrane is not 

 fluorescent. 



The scales of T. helena after most of the pigment has been 

 dissolved out still show their strong longitudinal and less- 

 marked transverse striae. 



The table on p. xxxix shows the effect of a few chemical 

 reagents, but it must be pointed out that acetic acid gives a 

 colourless solution slightly fluorescent in ultra-violet radiation 

 in the case of non-fluorescent species such as Diapliora mendica 

 and Abraxas ulmata. 



The discovery raises the question of whether the fluorescence 

 is of any value to the insects. It is generally accepted that the 

 male of Hepialus huniuli is coloured white in order to attract 

 the female during his hovering flight at dusk. The fact that 

 the white is fluorescent probably aids the female, which is 

 non-fluorescent, in her search. It is interesting that the 

 white males from the Shetlands are much less fluorescent than 

 English ones, those with red markings on a white ground only 

 very slightly fluorescent, and those coloured like females are 

 non-fluorescent. It is so light when the males fly in the 

 Shetlands, that the white coloration and fluorescence are not 

 of much use. 



In the case of the Geometers both sexes are equally fluores- 



