100 



STATE BOARD OF AGRICULTURE. 



Family APHIDIDiE. 



The "plant lice," or "green flies," or "Aphis": the first-named being the 

 term most usually employed. They have, when winged, two pairs of large 

 transparent wings, the anterior much the larger ; but some forms never develop 

 these organs of flight, and the oval plump bodies with long antennae, more or 

 less prominent honey-tubes near the anal end, and long legs will serve to identify 

 the colonies clustered about a stem or twig, or on the underside of a leaf. By 

 means of the honey-tubes the insects excrete a honey-dew on which a black 

 fungus develops and chokes the foliage. 



Fig 43. — Wheat plant louse ; much enlarged. 



The life history of many species is intensely interesting ; but briefly stated is 

 generally about as follows : They winter as eggs, from which, in the spring, 

 hatches a wingless form which in a few days begins to give birth to living 

 young resembling the parents, and, like them, viviparous, i. <?. , giving birth to 

 live young, and parthenogenetic, i. e., neither male nor female, capable of 

 bringing forth young without a previous union with a male. These young are 

 ready to reproduce in turn in a few days or a week, and from 4 to 8 young per 

 day may be produced under favorable conditions. 



Sometime in early summer winged individuals occur and these fly to other 

 localities or other food-plants. They are also parthenogenetic specimens and 

 they found colonies wherever they alight. In the fall, when frost appears and 

 food becomes scarce, the true sexes are produced and eggs laid. In some cases 

 the insects have alternate food-plants, e. g. the hop-plant louse which winters 

 on the plum, starts breeding there and migrates to the hop-fields only when 

 the vines are well started. With the approach of cold weather when the hops 

 are being harvested they fly back to the plums again, where they eventually 

 oviposit, only to begin the same cycle next year. 



