240 OUR INSECT FRIENDS AND FOES 



rather more than twenty stone, Professor Huxley 

 computes that the tenth brood alone of the des- 

 cendants of a single Aphis, if their multiplication 

 remained altogether unchecked by the usual 

 natural causes which play such an important 

 part in their destruction, would weigh more than 

 five hundred millions of stout men ! But for its 

 many natural foes, such as the insect-feeding 

 birds, and certain insects which feed upon it 

 or deposit their eggs in its living body, and 

 those storms and other sudden climatic changes 

 which exercise a very considerable influence 

 upon its numbers, the Aphis would multiply 

 to such a degree as to cause in a few months 

 the total destruction of all existing vegetation. 



And now let us just briefly glance at the 

 anatomy and general appearance of this most 

 remarkable and prolific insect foe. The male 

 Aphides are always winged, while the females are 

 frequently wingless. Throughout the summer 

 months the majority of the viviparous females 

 are wingless, but at certain times, particularly 

 when the food-plants are becoming exhausted 

 from the vast numbers of Aphides crowded 

 together, and in the spring and autumn, winged 

 females appear. The Aphides are chiefly 

 brownish or green in colour, often closely 

 resembling the colour of the food-plant, though 

 some species like the Bean Aphis, which is such 

 a pest in the kitchen garden, attacking the tops 

 of the broad-beans, is from its sooty colour often 

 called the " Collier " or " Black Dolphin." Their 

 bodies are soft, fleshy, and swollen in appear- 

 ance, more or less oval in shape, and generally 



