CHAPTER VII 

 BENEFICIAL INSECTS 



So much has been written about injurious insects that it seems 

 as though none are of value to man. This is not at all true, since 

 many insects pollinize flowers, others act as scavengers, and 

 a few produce lac, cochineal, tannic acid, medicines, and even 

 food for human beings. Besides these the silkworm and honey- 

 bee have become almost indispensable because of the silk, honey, 

 and wax they furnish. 



FIG. 38. Silkworm : A, caterpillar ; B, cocoon ; C, adult female moth. 

 (From Shipley and MacBride.) 



Silkworm. The silkworm (Fig. 38, A) is really a domesti- 

 cated animal, just as much as the horse, dog, or cat. It is the 

 caterpillar of a moth and has a life history as follows : The 

 female moth (Fig. 38, C) lays about three hundred eggs on pieces 

 of cloth or paper provided for it. When the caterpillars hatch, 

 they begin to feed at once on leaves of the mulberry, osage 

 orange, or lettuce. At the end of about six weeks they begin to 

 spin their cocoons (Fig. 38, B). The fluid which forms the silk 

 is produced in the silk glands of the caterpillars; it passes out 

 through the spinneret and hardens on coming into contact with 

 the air. The caterpillars first attach the thread to near-by 



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