OB, PLAIN TEACHING. 



The silk-worm (Bombyx rnori) , 

 17, produces silk, of which our 



richest dresses and decorative 

 furniture are made. It has been 

 estimated that the culture of the 

 silk-ivorm and the manufacture 

 of silk afford employment to a 

 million and a-half of people, and 

 create yearly a sterling value of 

 between thirty and forty millions 

 of pounds ! The cochineal insect 

 {Coccus cacti), male 18, female 

 19, produces 

 the valuable 

 dye known 

 as cochineal. 

 There are 

 about 70,000 

 insects to 

 a pound 

 weight. In ^ os - 

 1850, 2,514,512 pounds were im- 

 ported into Great Britain. The 

 annual value of the cochineal 

 consumed in Britain, alone, is 

 £370,000. To another individual 

 of this order {Coccus lacca), lac- 

 insect, we are 

 indebted for 

 a very valu- 

 able resin, 20, 

 which the 

 insect forms 

 and deposits 

 upon trees, 

 in the East 

 That which is sold as 



Indies. 



stick-lac is the unprepared resin, 

 still adhering to bits of the 

 branches. This, separated and 

 powdered, and decolourized, is 

 called seed-lac. When melted 

 and formed into cakes, it is called 

 shell-lac. With ivory-black it 

 makes blade sealing-wax, with 

 vermilion red wax, with lamp- 

 black it forms Indian ink. In 

 other states of preparation it 

 forms valuable dyes, varnishes, 

 and lackers. It also yields laccic 

 acid. Only the females, 19, arc. 

 thus productive. Amber, which 

 is used for various ornaments, is 

 also said to be formed in a similar 

 manner, by a large species of ant. 



We are indebted for oak galls, 

 so useful in the manufacture of 

 ink and various dyes, to the gall- 

 fly {Cynips 

 quercus), 1, 

 which punc- 

 tures the 

 leaves of the 

 oak, and de- 

 posits eggs 

 within, there- 

 by causing 

 the nut-like 

 excrescences, 

 2, which possess useful chemical 

 properties.* Several kinds of 



210 



locusts, D-180, are eaten as food by 



* For a further explanation, see "Our Walk in the 

 Woods". 



