INTRODUCTION xi 



preventing their reproduction or in actually imprisoning the 

 objects that might be damaged, as we do for ourselves with 

 barricades of fly screens and mosquito nets. Crude as such 

 methods may appear to be in general principle, their applica- 

 tion is by no means as simple as might appear at first sight, 

 and in practice they are becoming much more efficient from 

 year to year. 



Unfortunately the vast group of insects has furnished al- 

 most no species that are directly useful to man. Only two 

 stand out in sharp contrast; the honeybee and the silkworm. 

 Like some of our higher domesticated animals and cultivated 

 plants, they have been associated with man for many cen- 

 turies. Indeed the silkworm has its origin hidden in antiq- 

 uity and like our familiar plant, Indian corn, has never been 

 found in the wild state. Through selection, several improved 

 races of the honeybee have been evolved and apiculture as 

 now followed in many countries has added greatly to the 

 material wealth of the world through its extensive produc- 

 tion of honey and beeswax. 



The silkworm is likewise an extremely valuable insect, 

 although its cultivation is limited to a smaller part of the 

 world. All the real silk of commerce is produced by insects, 

 although certain kinds are spun by other caterpillars than 

 those of the true silkworm (Bombyx mori) . Like the ' honey- 

 bee, the silkworm is known in several races with special 

 characteristics of cocoon-color and rate of development, 

 brought about by selection and inbreeding. For many cen- 

 turies the silkworm has produced not only a vast amount of 

 valuable material for clothing and other purposes, but has 

 added immeasurably to the glitter of personal adornment. 

 Quite possibly in the future the product of the silkworm may 

 be supplanted by chemically treated wood-fibre and other 

 inferior materials of similar appearance. 



Shellac is also the production of an insect, of considerable 

 commercial importance, and something for which no accept- 

 able substitute has so far been evolved. It does not seem 

 improbable, however, that the lac-insect may become obso- 



