174 INSECTS AFFECTING VEGETATION 



ing short of a serious injury would attract attention, but the damage 

 is distributed throughout the growing season. As a general rule, 

 each species is most destructive at a different time from the other 

 species of that locality; hence, species of Cr ambus prey upon the 

 grass as a succession of small armies. Could the loss caused by these 

 species come at one time in the year their destructive power would be 

 better appreciated. Less than a third of the species may be classed 

 as of economic importance, but these possess a capacity to cause 

 almost infinite loss if the conditions are favorable. 



Besides the injuries to corn, grass, and oats already mentioned, 

 wheat and rye have been injured by vulgivagellus, tobacco by lute- 

 olellus (caliginosellus) , and cranberry by hortuellus, a species not yet 

 reported from corn. There are about sixty species of the genus 

 Crambus in the United States. So far as known they are of very 

 similar habit, and it is quite likely that any of them living habitu- 

 ally on grass will injure corn if this is exposed to their attack. The 

 species notably injurious to this crop will consequently depend, in 

 all probability, upon those which happen to predominate in the 

 grass at the time the field is plowed, and as these predominating 

 species differ from year to year, the list above given is not to be re- 

 garded as final. (Bui. 95, 111. Agr. Exp. Sta.) 



The young caterpillars form their web-lined nests immediately 

 upon or just under the surface of the soil, strengthening them by 

 the addition of bits of grass or particles of dirt to the surface. They 

 commonly cut off the blades of grass and draw the ends down into 

 the nest so that they can feed without leaving it. 



The facts concerning these web-worms all admonish the farmer 

 to break up a grassy turf as early in the fall as practicable prelim- 

 inary to planting the ground to corn ; the middle of September is as 

 late as safety permits. If, however, this is not done until spring, it 

 may best be postponed, so far as web-worm injury is concerned, in 

 most cases, until the latter part of May. If an infested meadow or 

 pasture is plowed earlier than this, when the larvae are still young, 

 they will probably live to attack the corn when it appears; and if 

 plowing is postponed later, until the first brood of moths have 

 emerged, they are likely to lay their eggs in the grass before plow- 

 ing, and thus to give origin to a brood of caterpillars, -which, being 

 quite young when the corn comes up, will make a long-continued at- 

 tack upon it, against which replanting will be of no avail. (Bui. 

 95, 111. Agr. Exp. Sta.) 



Burrowing Web-Worms. These species, treated among the 

 less important insects of the corn plant, are mentioned here merely 

 to distinguish the larva of this group from the other web-worms, 

 which it resembles somewhat in habit and injury to corn. It inhab- 

 its, however, a vertical cylindrical burrow penetrating the earth to 

 a depth varying from six inches to two feet or even more. It is about 

 the size of a common cut-worm, but differs by its dull velvety sur- 

 face and its colors, varying from silvery gray to brown, by the row r s 

 of polished spots on the body, and by its greater activity and more 

 loosely jointed structure. 



