84 INSECTS INJURIOUS TO VEGETATiLES 



Aphides or Plant-lice. — Nearly every one knows the plant- 

 lice or aphides, since there are few succulent plants that are 

 exempt from their attack. Many staple crops of the field, 

 garden, and orchard are very severely damaged when these 

 insects multiply in unusual numbers, as so frequently happens. 

 Aphides are also known as "lice," "aphis" and "green fly." 



There are many species, as varied in appearance as in habits, 

 and although they have attracted attention for years on account 

 of the injuries which they cause and their interesting habits, 

 they are perhaps less understood than any large group of insects 

 which could be named. In fact, \vc are not as yet able to estab- 

 lish beyond a certain degree of doubt the identity of some of our 

 most injurious forms and we know less of their life economy. 



Gardens are seldom free from their attacks, and cabbage and 

 like crops, melons, cucumbers and similar plants, peas and young 

 budding fruit trees suffer severely in some seasons. 



The best-known aphides are soft-bodied and green, very 

 minute in size, with long legs and antennae. Immense masses 

 of them frequently congregate on single plants, sometimes over- 

 running entire fields. If a mass be closely examined it will be 

 seen that many are wingless during the greater part of the 

 season; later, however, there are many which develop wings 

 and are capable of flight. There are many stages of these in- 

 sects, but the body is usually formed more or less like a pear, 

 and the winged forms have two pairs of very delicate trans- 

 parent wings with a few simple veins. The first and second 

 pairs of wings are usually connected as in wasps and bees, by 

 a booklet. The haustellum or beak by which aphides obtain 

 their food is three-jointed and of variable length. The eyes 

 are compound and project prominently at the sides of the head. 

 The aphides exude "honey-dew," a transparent fluid with 

 a sweetish taste. Frequently it is excreted in such quantity 

 that it forms a shining cover to the leaves of plants. The 

 honey-dew of most species is very attractive to a number of 



