STRAWBERRY INSECTS 383 



Illinois, Ohio, Maryland and Delaware. Its presence in a field 

 is sometimes first indicated by the drying out of plants in certain 

 spots; in other cases the plants generally have an unthrifty 

 look, and the fruit remains small and fails to ripen. It has been 

 found more troublesome on light sandy soils. 



The insect passes the winter as shining black elongate oval 

 eggs attached to the leaves and leaf stems of the strawberry plant. 

 These winter eggs hatch in early spring, giving rise to wingless 

 females which, when mature, give birth to living young. These 

 are all females, and reproduction continues agamically through- 

 out the growing season, males not appearing till the advent of 

 cold weather in the fall. At first the Uce feed exclusively on 

 the leaves and tender parts of the plants above ground, but 

 about the last of April in Delaware the little brown ant, also 

 known as the corn-field ant (Lasius niger americanus) becomes 

 abundant and carries many of the young aphids down to the 

 roots, where colonies are estabhshed that soon sap the vitahty 

 of the plant. The ants feed on the honey-dew secreted by the 

 aphids and care for them somewhat as we do for our domestic 

 animals. In case the plant dies or the roots become over- 

 crowded, they transfer their ''cows" to green pastures on some 

 near-by plant. 



Most of the aphids are wingless, but when the supply of food 

 becomes insufficient, winged forms are produced that fly to 

 neighboring fields where they are found by ants, and new colonies 

 are estabhshed on the roots. In Delaware these winged females 

 are most abundant in May and in June. The aphids multiply 

 with marvelous rapidity, one generation following another 

 about every two weeks. At the approach of cold weather 

 males and egg-laying females are produced ; the latter deposit 

 the winter eggs on the leaves and leaf stems above ground. 



Means of control. 



Much of the loss caused by the strawberry root-louse can be 

 avoided by setting clean plants on uninfested land. It is not 



