Ecology. 3D 
numerous day-flying moths of our heaths and moors are well-known 
examples. 
But several of our smart Vanessw have obviously been “ camp-followers’ 
and powerful migrants from a distant period, and chose as food plants the 
weeds that crowd upon the heels of our cattle, and those, moreover, that 
none but themselves can touch with impunity. Our gorgeous “yellows” 
and “whites” are, in this country, fed at man’s expense, and they the most 
notorious of migrant hordes. The little Davus still, however, flits the 
northern moors with his dingy suit of sable; blandina haunts the remnants 
of the sheltered moorland birch woods, simulating in his feeble flight and 
dusky colour his cousin of the southern birch heath. Many other insects 
too, peculiar to the moorland, have yet escaped the gradual but fatal advances 
) 
of the fire and drain. 
The insects of our chalk downs, where neither fire nor drain can reach, 
are exceptionally blessed, as all observers who have dwelt much in moorland 
districts can aver. Here the lovely “blues” reign over a kingdom rich in 
old-established associations, and attest the comparative harmlessness of sheep 
where artificial interference fails. 
The more highly organised forms of a natural association do not, indeed, 
merely take toll without helping towards its security as such. The wild 
boars that formerly rooted in our woodlands are believed to have been active 
agents in the regeneration of the ancient forest. Wolves kept the weaker 
grazing animals, so injurious to seedling trees, from undue increase, and 
chiefly restricted their wanderings to the open downs and uplands. Horned 
cattle owned the alluvial meadows, borders of the marshes and the woodland 
flushes, trampling all that obstructed them in browsing, and thus helping, in 
the yearly death and destruction, the harvest claimed by autumn floods. 
REFERENCES. 
1. GraEBNER, P. Pflanzengeographische Eindricke auf den Britischen Inseln, 
New Phytologist, June 1912. 
2, MEMBERS OF THE CENTRAL COMMITTEE FOR THE SURVEY AND STUDY OF 
British Veceration. Types of British Vegetation, edited by A. G. 
Tansley, M.A., F.L.S., 1911, Camb. Univ. Press. 
3. Crampron, C. B. The Geological Relations of Stable and Migratory Plant 
Formations, Scottish Botanical Review, pts. 1, 2, and 3, Jan., April, July 1912. 
4. Crampton, C. B. Vhe Vegetation of Caithness considered in relation to the 
Geology, 1911. Published under the auspices of the Committee for the Survey 
- and Study of British Vegetation. 
