A SYNOPSIS OF THE APHIDIDAE 9 



species differ considerably in structure from the spring migrants 

 (fundatrigenia). This is particularly noticeable in the Pemphiginae. 

 Many species are confined throughout the season to one species of host, 

 others to one or two or a few species, while still others may live on 

 any of a number of hosts (Aphis senecio Swain, Rhopalosiphum per- 

 sicae ( Sulz. ) ) . All sustenance is derived from the plant juices of 

 the various hosts, but each species is usually confined more or less 

 definately to feeding on some certain part of the plant. Some live 

 entirely upon the leaves, some on the stems of the leaves and small 

 twigs, some on the trunks and larger branches, some on the roots, 

 some on the flower heads and racemes of the host, and still others 

 feed on almost any part of the plant. The greater number of species 

 are free living, but certain of the Aphidinae form pseudogalls (Aphis 

 pomi De Geer, Aphis malifoliae Fitch, Phyllaphis coweni (Cockerell) ), 

 while the Pemphiginae and Chermisina form true galls. Nearly all of 

 the Pemphigina spend at least part of the season on various species 

 of Populus, the Schizoneurina on TJlmus, while the Lachnini and 

 Chermisina are practically confined to the conifers. The Aphidinae 

 are found mostly on deciduous trees and herbaceous plants, although 

 some live on conifers (Myzaphis dbietinus (Walker), Nectarosiphon 

 morrisoni Swain). 



ECONOMIC CONSIDERATIONS 



From an economic standpoint most of the species are of no 

 importance, although there are many that are well known pests of 

 cultivated crops. For example the woolly apple aphis (Eriosoma 

 lanigera) is a world-wide pest of considerable importance to the apple. 

 The green and the rosy apple aphis (Aphis pomi, A. malifoliae) do a 

 large amount of injury in certain localities, and are extremely difficult 

 to control. The rose aphis (Macrosiphum rosae) is known the world 

 over, and although living unprotected and easily killed with any of 

 the common contact insecticides, it is recognized by everyone who has 

 grown roses in the dooryard as an extremely troublesome pest. The 

 walnut aphis (Chroniaphis juglandicola) , the cabbage aphis (Aphis 

 brassicae) , the green peach aphis or greenhouse aphis (Rhopalosiphum 

 persicae) are all well known pests. The common contact insecticides 

 are usually efficient for their control. Many species are kept well 

 in check by their predaceous and parasitic enemies, the ladybirds, the 

 syrphid flies, the lacewings, and the braconids. Of the ladybirds, 

 probably the most efficient in California are Coccinella californ-ica 



