480 ECONOMIC ZOOLOGY AND ENTOMOLOGY 



The Pea Aphis (Macrosiphum pisf). This large green aphis 

 sometimes appears on the peas in such numbers as to weaken 

 very much or even to kill the plants. The insects pass the 

 winter on clover and vetches, sometimes doing considerable 

 injury to these plants. They are usually fairly well controlled 

 by natural enemies and fungus diseases, but it is sometimes 

 necessary to resort to spraying in order to save the crop. 

 Whale-oil soap or some of the tobacco washes may be used. 

 Considerable force must be used in applying the spray. It is 

 sometimes practicable to brush the aphids from the vines and 

 destroy them by covering them with soil. Clover and peas 

 should not be planted close together. 



The Bean Thrips (Heliothrips fasciatus) . In many places on 

 the Pacific coast this is the most serious pest of the peas and 

 beans. It also does a great deal of damage to tomatoes, po- 

 tatoes, alfalfa and many other cultivated and wild plants. 

 The black-bodied little insect, with its four narrow, hair- 

 fringed wings, is so small that it rarely attracts attention even 

 when present in great numbers, and its presence is usually 

 not suspected until the leaves of the plant begin to turn yellow- 

 ish and dry up because the sap has been sucked out. There 

 are six or seven generations during the year. The young 

 are wingless and whitish, often with reddish markings on the 

 sides of the body. 



Because the insect feeds more commonly on the underside of 

 the leaves, and on account of the nature of the crops that it 

 infests, it is rarely practicable to control this pest by spraying. 

 We must depend, then, upon the natural enemies of the thrips, 

 and clean culture methods, for control. As this thrips feeds 

 on many weeds, particularly on wild lettuce, these should be 

 kept out of the garden and nearby fields. 



CABBAGE 



The Imported Cabbage-worm (Pontia rapes). This is the 

 most common of a number of butterfly and moth larvse that 

 feed on cabbage. Before this species was introduced into 

 America, more than fifty years ago, the larvae of some of our 

 native butterflies belonging to the same genus were often 



