292 TROPICAL NATURE III 
tion of very large, there is a corresponding increase in the 
numbers of very small species. The much greater size reached 
by many tropical insects is no doubt due to the fact that the 
supply of food is always in excess of their demands in the 
larva state, while there is no check from the ever-recurring 
cold of winter ; and they are thus able to acquire the dimen- 
sions that may be on the whole most advantageous to the race, 
unchecked by the annual or periodical scarcities which in less 
favoured climates would continually threaten their extinction. 
The colours of tropical insects are, probably, on the average 
more brilliant than those of temperate countries, and some of 
the causes which may have led to this have been discussed in 
another part of this volume. It is in the tropics that we 
find, most largely developed, whole groups of insects which 
are unpalatable to almost all insectivorous creatures, and it is 
among these that some of the most gorgeous colours prevail. 
Others obtain protection in a variety of ways; and the 
amount of cover or concealment always afforded by the 
luxuriant tropical vegetation is probably a potent agent in 
permitting a full development of colour. 
Brirps 
Although the number of brilliantly-coloured birds in almost 
every part of the tropics is very great, yet they are by no 
means conspicuous, and as a rule they can hardly be said to 
add much to the general effect of equatorial scenery. The 
traveller is almost always disappointed at first with the birds, 
as he is with the flowers and the beetles ; and it is only when, 
gun in hand, he spends days in the forest, that he finds out 
how many beautiful living things are concealed by its dense 
foliage and gloomy thickets. A considerable number of the 
handsomest tropical birds belong to family groups which are 
confined to one continent with its adjacent islands, and we 
shall therefore be obliged to deal for the most part with such 
large divisions as tribes and orders, by means of which to 
define the characteristics of tropical bird-life. We find that 
there are three important orders of birds which, though by 
no means exclusively tropical, are yet so largely developed 
there in proportion to their scarcity in extra-tropical regions, 
1 Chapters v. and vi., post. The Colours of Animals and Plants, 
