2 
INTRODUCTION 
only a degree less effectual. In an area of this kind the few insect 
inhabitants are such as have adapted themselves, like so-called 
“ weeds of cultivation,” to the very special conditions superimposed 
by the sustained operations of the patient husbandman. Such 
insects, “ our garden friends and foes,” to use the apt title of one of 
the works of the late Rev. J. G. Wood, are often found, like the 
aforesaid weeds of cultivation, to enjoy a wide distribution . 1 Yet 
even in well cultivated areas one may happen on oases, so to say, 
patches of land too wet, or perchance too dry, for profitable cultiva¬ 
tion, where many of the indigenous plants survive, and with them 
some at any rate of the indigenous insects. 
Since it would appear that, in spite of all that has been written 
on the subject during the last fifty years, there is still a good deal of 
misapprehension as to the sense in which certain expressions are 
used by naturalists, it seems desirable to say a few words on the Use 
of Metaphor in Natural History. 
We may perhaps assume that now-a-days no one thinks that by 
the term Natural Selection it is suggested that Dame Nature walks 
about pulling up the weaker seedlings, or stamping on worms that 
are slow to get out of the way. Probably the use of the happier 
term “ Survival of the Fittest ” has abolished such crude ideas, but 
the habit of literal interpretation dies hard. 
Flies are for the most part very defenceless creatures and have 
little save the swiftness of their movements to protect them from 
their enemies. On the contrary bees and wasps are formidable 
animals well armed for attack or defence. It is common knowledge 
that many flies are so like bees or wasps as to be readily mistaken 
for them. Such a fly is said to “ mimic ” the bee or wasp that it 
resembles. The bee or wasp is termed the “ model.” There is good 
reason to believe that the resemblance is a real protection to the fly, 
since of its various enemies some, at all events occasionally, mistake 
the defenceless “ mimic ” for the well armed “ model .” 2 
Again certain butterflies, which we have reason to believe afford 
palatable food to birds and other creatures, are so like certain other 
butterflies (belonging to widely different groups) which in their turn 
are believed on good evidence to be distasteful to birds, etc., that, 
especially during life, the one may be readily mistaken for the other. 
In such a case the palatable butterfly is said to “mimic” the distasteful, 
and the two are spoken of as “mimic” and “model” respectively. 
1 For notes on some widely distributed Lepidoptera, see Chapter X., § 12. 
2 For recent experiments see R. I. Pocock, F.L.S., in Proc.. Zoolog . Soc., Lond., 
1911, pp. 853-855. 
