212 A BOOK OF TNSECTS 



to Europe, where, especially in France, it has caused in- 

 calculable damage in vineyards. The life-cycle of this 

 insect is no less complex than that of Chermes, but the 

 various generations migrate between the leaves and the 

 roots of the same plant — the vine — and not from one 

 kind of plant to another. Gall structures are formed both 

 on the leaves and the roots. An allied aphid known as 

 Phylloxera punctata may be found in England on the 

 underside of oak leaves. This is probably the only con- 

 gener of the vine Phylloxera, and Lichtenstein says that 

 " in its cycle, from the starting-point of the winter-egg 

 to the assumption of the sexual condition, it exhibits a 

 series of no less than twenty-one forms." 



Many kinds of aphides and their allies produce large 

 quantities of a sweet liquid to which the name " honey- 

 dew" is usually applied. It appears in drops from the 

 end of the abdomen. In some species an individual has 

 been observed to emit as many as forty-eight drops, each 

 about 1 mm. in diameter, in the course of twenty-four 

 hours. Honey-dew accumulates as a sticky deposit on 

 the leaves of plants, and is eagerly sought after by many 

 kinds of insects, especially ants. Indeed, ants have dis- 

 covered the origin of the sweet food, and actually obtain 

 it direct from the aphides, which on this account have 

 been called their " cows." One may watch them running 

 about among a flock of aphides, and eagerly seizing the 

 glistening drops as they exude ; while there is reason for 

 thinking that an aphid voluntarily surrenders its store of 

 sweetness in response to the caress of an ant's antenna?. 

 Ants are essentially mandibulate insects. They can bite 

 and they can lick ; but they have no elaborate piercing and 

 pumping apparatus like an aphid, no complex " tongue " 

 like a bee, no sucking-tube like a moth. Thus, to obtain 

 the sweet juices which constitute so large a part of their 



