Lepidoptera. 169 



surface is varied, hence also its flora, and therefore we get a 

 good number of species of lepidoptera. One of our members 

 recently pointed out that in Northumberland and Durham, 

 where intrusive dykes of Basalt had converted the limestone 

 into a crystalline form, known as the " sugar limestone," the 

 flora was of a distinctly marked type. As, therefore, the 

 larvae of our butterflies and moths have all their special or 

 favourite haunt where the food-plant occurs, we must expect to 

 find the distribution of insects also affected by the geological 

 characteristics of the country, and the vegetation prevailing in 

 it. As an instance of this we generally find L. corydon in 

 profusion on such chalk hills as Riddlesdown, S. semelc the 

 same, V . urticcs in waste fields where plenty of nettles grow, 

 C edusa in clover or lucerne fields, Traclicea pinipcrda and 

 Fidonia piniaria in pine woods, Anarta myrtilU and S. carpini 

 on heaths, &c., so that as we have about Croydon oak-woods, 

 pine-woods, heather-covered hills, chalk downs, and cultivated 

 fields, we have the lepidoptera usually found in such localities, 

 for the reason that their larvae feed on the plants that distinguish 

 them. 



Besides this it has been noticed of late years, not only in 

 Croydon, but in other places near London, that a kind of false 

 insect fauna is obtaining, and the reason is this : building is 

 spreading rapidly and surely, and with it gardens are made and 

 trees are introduced, and fresh food is furnished for species 

 which were once uncommon, so that now Park Hill alone pro- 

 duces more Smcrinthus occellatus, tilics, popjili, S. Ugiistri, 

 and C. vimda, than the whole district did when it was clothed 

 with its natural vegetation, such species being able to multiply 

 extensively, owing to the wide (and highly gratifying) planting 

 of poplars, limes, willows, lilacs, &c. 



Whilst, therefore, we are losing a large number of species 

 in our immediate neighbourhood, owing to the advance of 

 railways, roads, and buildings, destroying their food-plants, 

 we are at the same time obtaining a larger number of such 

 species as feed upon the various trees and shrubs introduced 

 to modif}' the effects of such inroads. 



Such observations as these are not only of great interest in 

 themselves, but are of considerable value from more than one 

 point of view, and this brings us to notice another, or rather 

 two other matters of importance. One is the effect of weather 

 and seasons upon insect life, and the second is the effect of 

 insect life upon our farms, orchards, and gardens. 



As regards the former, it is generally thought, and even 

 stated in black and white, that a severe winter has a destructive 

 effect upon insect life, and in fact upon what is termed by 



