60 THE MONTHLY BULLETIN. 



or about the time the first buds are sufficiently swollen to show the tips 

 of the opening leaves. Some species, notably the green peach aphis, 

 Myzus persicfx, hatch so early that the stem-mothers (the lice from 

 the eggs) may be fully grown and be giving birth to living young of the 

 second generation before the buds open enough to show the green of 

 lite expanding leaves. 



It is common for the viviparous lice to give birth to living young at 

 the rate of five to eight or ten a day, until each becomes the parent of 

 50 to 100, or even more. It is common for aphids to mature and begin 

 giving birth to living young at the age of from seven to ten days, so 

 that ten or twelve broods a year is not a large number. The descendents 

 of one louse passing through ten generations of 50 each, provided all 

 find a normal food supply and escape the attacks of their natural 

 enemies, would be approximately two quadrillions. If they were all 

 martialed, 150,000 abreast, in close enough order so that each could 

 place its antenna? upon the closed wings of the louse in front, they 

 would make a procession long enough to reach around the world. These 

 figures are entirely beyond our comprehension and are of little use 

 except to aid us in appreciating the wonderful balance that nature has 

 established among her myriads of living creatures with their wide 

 diversity of habits. The balance would not be complete with one of 

 these species left out. In a study of the Aphidiclce in their relation to 

 other living forms, we surely have, in the words of Pope, "A Mighty 

 Maze, but not without a plan." It is a marvelous natural balance and 

 interrelationship of living things that can hold such a possibility of 

 development so completely in check and yet not exterminate a single 

 form, except at long intervals, and then only by allowing some other 

 to take its place. When the balance is upset for a brief time for some 

 species it is probably due, in most cases, to the meddling hand of man, 

 who, more than storm or tempest or earthquake, has greatly changed 

 the face of nature and used her most powerful and subtle forces to do 

 the bidding of his fitful mind. Now man must use the highest powers 

 of his God-given intellect to ward off or overcome the evil effects that are 

 fast coming to him as the direct result of his interference with nature's 

 plan. It is a good illustration of the Great Law of Compensation of 

 which Emerson wrote. 



It is not enough that aphids should have great powers of reproduction, 

 for this alone would not save them from extinction. As soon as a 

 colony becomes established one or more of the enemies mentioned above 

 makes its appearance and begins to devour the lice so rapidly that all 

 would be destroyed were it not for the power of flight which some of 

 the individuals acquire enabling them to go in search of distant food 

 plants where, for a time, they may establish new colonies away from 

 immediate danger. While the power of flight is of great service to the 

 species during the summer, it would not do for the stem-mothers 

 hatching from the eggs to fly away from their natural food plants upon 

 which the eggs were laid the previous fall, as some of them might 

 wander and be lost, so they are always without wings and have to stay 

 at home and attend strictly to the raising of their numerous families. 



Another most wonderful habit possessed by many of the plant lice 

 seems to have for its chief purpose the protection of the species from 

 the terrible onslaughts of its enemies. It is that of suddenly changing 



