PYGMY WORKERS AND BUILDERS. 109 



ing no more chance against its tiny foe than has a rab- 

 bit against a weasel. If the aphis have its beak deeply 

 plunged into the bark, the ichneumon-fly has an easy task, 

 for the aphis can do nothing but kick and struggle, while 

 anchored to the spot by its proboscis, and all that the ich- 

 neumon-fly has to do is to make its deadly lunge. But, if 

 the aphis be wandering about the plant, the ichneumon- 

 fly has to walk about with it, and try first one side and 

 then the other, until she can find an opportunity of deposit- 

 ing her egg. ^ j- ft Wwd _ 



SPINNERS OF THE MULBERRY-TREES. 



1, Of all the insect tribes, the ways and transformations 

 of the mulberry silk-worm are probably the best known. 

 The accurate and minute knowledge which we have of this 

 insect is owing to the fact that success in the production 

 of silk is rendered possible only by carefully studying every 

 phase of the life of the silk-worm, and by providing the 

 conditions necessary to its healthful development. There 

 are many varieties of silk-producing worms, each feeding 

 upon the leaves of some special plant, but only a few whose 

 products can be successfully and economically manufac- 

 tured. Within a short time past successful experiments 

 have been made with the varieties which feed upon the oak 

 and the ailanthus, but still the spinners of the mulberry- 

 trees continue to furnish the greater part of the world's 

 supply of silk. 



2. The silk-worms are hatched from eggs about the size 

 of a mustard-seed, an ounce of eggs producing from thirty 

 thousand to forty thousand worms. Scarce is the worm 

 born than he begins to eat. Indeed, it has no time to lose, 

 for, before reaching maturity, it must gain seventy-two 

 thousand times its own weight ; so, to acquit itself con- 



