INSECTS INJURIOUS TO CLOVER 



211 



The Pea-louse * 



Although this aphid is worst as a pest of peas (see page 322 

 for full account) it passes the winter on red and crimson clover 

 which occasionally are seriously injured. In the spring of 1900, 

 both red and crimson clover were badly injured in Delaware, 

 Maryland and Virginia, while in DeKalb County, Illinois, con- 

 siderable acreages were entirely destroyed in August, 1903, and 

 more or less injury has been done since then. Where peas are 

 available the aphides migrate to them in the spring, but other- 



FiG. 151. The pea-aphis: 1, winged viviparous female; 2, wingless vivip- 

 arous female greatly enlarged. (After Folsom.) 



wise they continue to multiply on the clover. In late fall they 

 return to the clover upon which the eggs are laid, in which stage 

 the winter is passed, though in open winters many of the viviparous 

 females live over winter on the clover. 



Control. This is another pest which is usually held under 

 control by a fungous disease, and as the fungus does not develop 

 in dry seasons, with dry weather the aphis increases unchecked, 

 while with a normal rainfall it is usually held in subjection, 

 Unfortunately we are unable to predict the weather probabilities, 

 and when the aphides are found present on clover in considerable 

 * Macrosiphum pisi Kalt. Family Aphidida. 



