VARIATION OF EUROPEAN LEPIDOPTERA. 99 



test of fertile union with type was given as being the distinction 

 between varieties and aberrations. 



The Author then dealt with the moot question of the influence 

 of food in producing variation, and exhibited a specimen of 

 Melitcea artemis, which had been one of a vast army which 

 appeared first in the larval stage in a locality in the county Clare, 

 Ireland, and covered some fields with myriads of starving cater- 

 pillars, of which this one survived, and with numbers of others 

 emerged next season, a stunted and pallid insect, no larger than 

 the Alpine var. merope, and almost as faintly coloured. The 

 stint of food, either by accident or by the effect of climate 

 stunting the food plant, affects the size of the insect in all stages. 

 Many of the higher Alpine Erebics exemplify this in their 

 dwarfed proportions, while insects in arid tracts in South Europe, 

 whose food product has been stunted by drought, exhibit the 

 same diminution of size. But it was pointed out that diversity 

 of food did not produce variation in colour so usually as is 

 commonly thought. One or two instances, such as Abraxas 

 grossulariata, in which immediate aberrations are procurable by 

 change of diet, were admitted, but these the author considered 

 exceptional, and even when the larvae were altered greatly in 

 colour the imagines appeared of the normal tj^pe. 



An instance of Cleora lichenaria, bred by the Rev. Joseph 

 Greene upon an orange-coloured lichen, having orange spots 

 scattered over the wings, was thought to have been an effect of 

 mimicry, by which some of the variable species of Geometers, 

 which rest with wings outspread, assimilate their colouring to 

 that of the wall or tree trunk on which they settle. 



The effect of climate was stated to be diverse in the case of 

 the diurnal and nocturnal sections of Lepidoptera, the Heterocera 

 of subalpine and polar regions having well-defined patterns and 

 generally deepened tones of colour, while the Rhopalocera become 

 bleached in hue and blurred in definition. The light and heat of 

 the sun was shown, by examples of Central and South European 

 butterflies, to render colours more warm and brilliant, while white 

 is often replaced by silver, and coloured spots — as in some of the 

 Lyesenidse — shine with metallic lustre as we travel south. 



The effect of the law of heredity was next touched upon, and 

 its power of rendering the type permanent in the case of some 

 species was shown to be most potent, some butterflies, such as 



