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CHAPTER VII. 



APHIDIDxE (Green-fly). 



Throughout the -whole country no ch^ss of insects is more universally 

 distributed or more deserving of the appellation " injurious " than the 

 AphididcB or "Green-fly." The term blight is adopted for the de- 

 struction accruing from this class of insects, which are individually 

 small in size but collectively most injurious. They are to be found 

 on almost every plant, and are soft-bodied insects, with comparatively 

 long legs which are but poorly adapted for leaping. They are always 

 found in two principal forms — viz., winged and wingless ; and the 

 largest are never more than a quarter of an inch in expanse of wings. 



The body of the aphis is pear-shaped. The head, which is small 

 in comparison with the rest of the body, has two compound eyes, and 

 in the perfect stage ocelli or supplementary eyes are often present, — 

 a feature which is well worth special consideration from a physiolog- 

 ical point of view. During the larval stage the eyes are very con- 

 spicuous. In fact, they are often quite obvious in the embryo stage, 

 before the larvge quit the eggs. They vary in colour from ruby red 

 to brown or even black. 



The beak, which is always an important organ in insect structure, 

 is peculiarly adapted to the destructive demands of the creature, and 

 just shows that all insect anatomy is a modification of similar parts 

 to meet the needs of the creature. The beak proper is composed of 

 three joints, which vary in length according to genus and species. 

 Thus in the StomaiihU, a species living on oak, the beak is longer 

 than the body, while in the genus Chermes it is very small indeed, 

 the mouth being adapted to the food-plant. The former lives on oak 

 deeply furrowed ; the body reposes on the outer hard bark, while 

 the long proboscis is a necessity to reach the bottom of the narrow 

 fissure, where the juice can only be found. On the other hand, the 



