THE INSECT WORLD. 



but, of course, as in other groups, we have modest species in 

 which gray predominates, and where the longitudinal markings 

 are rather in the form of black Hues or streaks. The majority of 

 the species belong to the old genus Crm7ibus, and a number of 

 them are injurious in grass lands, where the caterpillars are 

 known as ' ' root web-worms. " As in many other cases, it is not 

 so much the grass that is injured as the corn crop which follows 

 it, and, therefore, we usually find them injurious in proportion 

 to the length of time that a field has been in grass before being 

 ploughed for corn. Usually the moths appear quite early in spring, 

 and the eggs are laid in grass some time in May, loosely attached 

 to blade or stem, or sometimes simply dropped on the ground. 

 The larvae, when they begin feeding, make a loose web or tube 

 of silk, sometimes on the surface, sometimes a little below it. 

 Occasionally they feed upon the roots, sometimes on the stalk, 

 and often they enter and bore into the plant itself If an infested 

 grass-plot is ploughed after eggs have been laid or after the cater- 

 pillars have hatched, such of them as survive attack the corn, if 

 that is the crop planted. Occasionally entire fields are destroyed, 

 while quite frequently much damage is done. The moths make 

 their second appearance a little after midsummer, and are never 

 troublesome then, because the eggs are laid in grass lands, where 

 the caterpillars, though abundant, are not noticed. From this 

 general life history it will be seen that fields can be kept clear by 

 fall ploughing, or by turning the sod very early in spring before the 

 moths have made their appearance or had an opportunity to de- 

 posit eggs. Bare ground will not become infested, nor, usually, 

 will a corn-field if there is any grass in the vicinity. Where 

 injury is caused on lands ploughed late, I have found that certain 

 commercial fertilizers exercise a beneficial effect ; in fields fertil- 

 ized with potash in the form of kainit or muriate, the exemption 

 may be complete, while in adjacent plots fertilized with barn- 

 yard manure, injury may be serious. It is also possible to pre- 

 vent trouble by planting some other crop between sod and corn, 

 where such rotation can be profitably adopted. 



In the genera Diatrcsa and Chilo we have insects resembling 

 those already described, but rather larger, with often more slen- 

 der pointed wings and longer palpi and abdomen. Here the 

 larvae are usually borers, some in corn, some in sugar-cane, and 



