ENTOMOLOGY 193 



able to get a migratory start, or, in fact, become abundant enough to 

 necessitate migration. 



One of the best remedies available in this latter direction is the 

 old-time one of plowing a furrow with its perpendicular side toward 

 the field to be protected and the subsequent dragging of a log through 

 the furrow to keep the earth friable and kill the worms which have 

 accumulated in the ditch; another is to poison heavily with Paris 

 green or London purple in solution a strip of pasture or field crop 

 in advance of the traveling army of worms. In the same line is the 

 distribution of quantities of a bran, arsenic, and sulphur-sugar mix- 

 ture across their line of march. The general destruction of the 

 worms themselves by direct application is hardly practicable, and as 

 a rule they can be safely left to the action of their natural parasites, 

 which at this season are apt to be very much in evidence. 



The Wheat Sawflies. There are quite a number of sawfly larvse 

 which are occasionally found in wheat fields. Most of these have 

 very little economic importance and are only chance migrants to 

 wheat from various wild grasses on which they normally feed. When 

 seen, however, by the farmer they often arouse fears and are charged 

 with damage with which, very likely, they have nothing to do. 



The adult insects are four-winged flies, belonging to the order 

 Hymenoptera, which includes the bees and wasps. They are termed 

 sawflies in description of the sawlike ovipositor of the female insect 

 with which she makes incisions in the tissues of plants for the inser- 

 tion of her eggs. The larvse of the species working on wheat either 

 bore the stems or feed externally on the leaves. The stem-borers are 

 the more distinctively wheat pests and are capable of doing much 

 more damage. 



Stem-Boring Sawflies. Two species may be especially noted as 

 being of possible importance in this country : First, the so-called Eu- 

 ropean corn fly and a native species which occurs in California and 

 works in a similar manner in the stem of a hollow grass. 



The adult flies appear in April and deposit eggs in the stems of 

 the young wheat. The larvse bore through the joints and work up 

 and down the full length of the stem. When full grown they attain 

 a length of half an inch and are milky white in color. With ap- 

 proaching harvest they pass down to the bottom of the stem and cutv 

 the straw circularly on the inside, nearly severing it. Beneath this 

 cut they form a little cocoon at the base of the stem, within which 

 they pass the winter in the larval stage, transforming to pupa3 and 

 emerging as adult insects the following summer. The object of the 

 cut made just above their cocoon is to cause the straw to break and 

 allow the perfect insect to more readily escape from the stem, and 

 the damage done by this insect is chiefly in the falling or lodging of 

 the grain which often results from the weakening of the straw at the 

 point indicated. Otherwise very little harm results, and the heads of 

 attacked wheat are, as a rule, well filled. 



This insect breeds in wheat in preference to other small grains. 

 Jn fact, it is doubtful whether it often successfully develops in other 



