INTRODUCTION 
If the stay-at-home naturalist should suppose that everywhere 
within the Tropics insects are more plentiful than in the Palaearctic 
Eegion he would make a great mistake. More varied they may be— 
and this is especially true of South America—but not necessarily 
more numerous. The veteran naturalist Dr. A. E. Wallace, in his 
“ World of Life ,” 1 emphasizes the fact that gregarious plants are far 
more prevalent in Temperate latitudes than they are in the Tropics. 
Plants such as heather, gorse and the like cover immense tracts of 
country; while extensive woods are often composed of oaks, beeches, 
or pines almost to the exclusion of other trees. A tropical forest 
contains many more species of trees to the square mile than would 
be found in Europe, Siberia or Canada. Masses of vegetation 
consisting of few species do not favour a very varied insect fauna, 
but may be quite compatible with a large insect population. In the 
more favoured parts of England butterflies make up in numbers for 
what they lack in variety. At the same time while it must be 
admitted that within the Tropics butterflies are more familiar objects 
than in Great Britain, it is certainly the case that insects need 
looking for in all countries alike; over large areas they may be 
comparatively scarce, whereas in favoured spots they will be found 
in great abundance. Such spots are open spaces in woods, whether 
natural or the work of man, exposed to the morning sun and well 
supplied with a variety of flowers; they are likely to be especially 
productive if water be also at hand. For some reason as yet 
unexplained the tops of hills, more particularly somewhat isolated 
knolls surrounded by woods, have a great attraction to many insects, 
notably swallow-tailed butterflies. On the other hand woods of a 
uniform character, especially if dense, may be quite poor as hunting 
grounds. Least productive of all are lands which have been long 
and well cultivated to the extermination of the aboriginal flora; nor 
must it be forgotten that tillage is not the only agricultural operation 
that displaces the native plants, for the constant and systematic 
grazing of land by cattle, sheep, camels and still more by goats, is 
