488 THE SMALL GRAINS 



country, but is a recognized pest in Europe and particu- 

 larly bad in France. The adult flies deposit eggs in the 

 culms of the young wheat in April, and the resulting larvae 

 bore through the joints and work up and down the culm 

 inside. When full grown they are \ inch long and milk- 

 white in color. Near harvest they pass down to the bot- 

 tom of the culm, and girdle the straw on the inside, nearly 

 severing it. Beneath the girdle a cocoon is formed in 

 which they pass the winter still as larvae, but transform 

 to pupae, and then adult insects the following spring and 

 summer. The object of the girdle is that the straw may 

 break and allow the perfect insect to escape, and the chief 

 damage done is in the lodging of the grain resulting from 

 this weakening of the culm. The insect prefers wheat, 

 but develops also in rye, and the females will oviposit 

 in oats and other grasses (Marlatt, 1901, pp. 34-38). . 



The ivestern wheat sawfly (Cephus occidentalis, Marlatt) 

 is a native species but similar in habits to the Euro- 

 pean wheat sawfly, and resembles the latter closely 

 in the adult form. It occurs in California and most of 

 the extreme northwestern states, particularly in North 

 Dakota, where it was reported as damaging as high as 

 25 per cent of the wheat in 1909. The larvae work in the 

 culms of grasses, but the insect may be expected any time 

 to change its feeding habits from grasses to small grains. 



Grass sawfly. The larvae of several leaf -feeding saw- 

 flies have been found on wheat. Probably the most 

 important is the grass sawfly (Pachynematiis extensicornis, 

 Nort.). It is about the size of the common house fly, and 

 occurs in the northern states east of the Rocky Moun- 

 tains. The eggs are inserted in rows along the edge of 

 the blades of wheat, or more commonly in grasses, and the 

 larvae feed on the leaves, more or less gregariously at 



