848 INSECTS AND BIRDS 



orchard. Many farmers believed that in time every un- 

 sprayed apple, peach, plum, and pear tree would be killed. 

 Here and there, however, some trees were seen to be hold- 

 ing out, showing little damage. It was generally thought 

 that such trees had greater power of resistance to the 

 ravages of the scales. This may be true but cannot be 

 taken as a full explanation of the facts. Unnoticed to the 

 eye of nearly all fruit growers, a tiny worm was at work, 

 within the body of the scale. This worm is hatched from 

 an egg inserted into the scale by a small wasp-like insect 

 about one fiftieth of an inch in length. This parasitic 

 worm, and its near relatives, have now, for the present at 

 least, exterminated the San Jose scale in parts of the 

 Eastern states. 



In the course of time it is probable that this beneficial 

 parasite may be so reduced in numbers on account of the 

 destruction of the food for which it has formed a liking, 

 or, by still smaller parasites living on itself, that the few 

 scales unparasitized may start to increase again at an enor- 

 mous rate until their parasite can once more multiply to 

 such numbers as to check them. So nature maintains her 

 balance. 



256. Bees. When we were studying about cross-pol- 

 linating flowers, bees were mentioned as pollen carriers. 

 In this respect they are very beneficial. But bees are also 

 valuable for the honey which they make. Beekeeping 

 throughout the world is a very old industry ; and in 

 America thousands of colonies are maintained for this 

 purpose. 



As is well known, bees live in colonies. Each colony is 

 made up of workers, drones, and a queen. The workers 

 are undeveloped females, whose business is to gather pol- 

 len and nectar. The drones are the males. The queen 

 is the only fully developed female. She lays the eggs. 



