INSECTS IN RELATION TO MAN 413 



vegetable matter. This function of insects is most noticeable in the 

 tropics, where the ants, in particular, eradicate tons of decomposing 

 matter that man lazily neglects. 



Of insects that are directly useful to man, the silkworms and the 

 several species of honey bees are the most important. Silk is most 

 valuable as a textile material, but has minor uses. Some of the best 

 fishing lines are made of silk; and the best "leaders" long, tapering, 

 strong, and practically invisible in the water are the silk glands them- 

 selves, after being stretched and dried. These leaders are imported 

 from the Mediterranean region, but may easily be made from the glands 

 of our large native silkworms, such as the Cecropia. 



Though honey as a food is not as indispensable to us as it was to the 

 ancients, immense quantities of it are produced annually, and the 

 demand for it is usually greater than the supply. Beeswax has more 

 uses than one might suppose. One of its chief uses is for the manufac- 

 ture of comb "foundation" for bee hives. Beeswax, though rivaled by 

 paraffin and ceresin, is better than these for some purposes. It is used 

 in polishes for furniture, floors, carriages, automobiles, shoes and other 

 leather articles, and steel tools; as a coating for shoemaker's thread and 

 for steel nails; as an ingredient of some varnishes; for the insulation of 

 electric wires, etc.; for church candles; salves and cosmetics; in sealing 

 wax and grafting wax; by sculptors for making models; by dentists for 

 taking impressions; and was anciently used on writing tablets. 



Lac, commonly used as shellac and for lacquer and other resistant 

 varnishes, is yielded by several species of scale insects, but chiefly 

 Tachardia lacca, which is abundant in many parts of India on a variety 

 of plants (Zizyphus, Acacia, Butea, etc.). The lac is a resinous secre- 

 tion, produced abundantly by the female, and forming with the exuviae a 

 protective covering over her body. 



A coccid that produces considerable quantities of lac occurs in 

 Arizona on Larrea mexicana. 



Several coccids of the genus Ceroplastes, in India and China, produce 

 white wax, which is highly valued for some purposes but has been 

 replaced by paraffin for other uses. 



The brilliant crimson pigment of the lac-insect of India is extracted 

 and known to artists as "lake." 



The cochineal insect, Dactyhpius coccus, is indigenous to Mexico, 

 but has been transported with its food plant, the prickly pear, to Spain, 

 India, and elsewhere. From the dried bodies of the females, carmine is 

 extracted. The cochineal industry, which dates back to the time of the 



