130 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



Grass-stem Saw-fly (Cephas occidcnlalis Riley and Marlatt). 

 This is a native species which normally lives in wild grasses and 

 which has been quite injurious in certain sections of the North- 

 west during recent years. It habits and the means of control 

 are practically identical with the species here discussed. f 



The following is gleaned from Professor Comstock's interesting 

 account. 



Injury. No external indications of injury to the plant can 



be seen until the larva within 

 has almost completely tunneled 

 the stalk, at which time there 

 is a discoloration just below the 

 injured joints. Thus damage by 

 this insect is not readily noticed, 

 it merely dwarfing and stunting 

 the growth of the plant by bor- 

 ing in the stem. 



" If infested straws be ex- 

 amined a week or ten days before 

 the ripening of the wheat, the 

 cause of this injury can be found 

 at work within them. It is at 

 that time a yellowish, milky- 

 white worm, varying in size from 

 one-fifth to one-half an inch in 



FIG. 94. The wheat saw-fly borer 

 (Cephus pygmoeus Linn.): a, ou 4 - 

 line of larva, natural size ; b, larva, 

 enlarged ; c, larva in wheat-stalk, 

 natural size; d, frass; e, adult 

 female;/, Pachyonerus calcitrator, 

 female, a parasite enlarged. 

 (After Curtis, from "Insect Life.") 



length. The smaller ones may 

 not have bored through a single 

 joint; while the larger ones will 

 have tunneled all of them, except, 

 perhaps, the one next to the ground. 



Life History. " As the grain becomes ripe the larva works 

 its way toward the ground; and at the time of harvest the greater 

 number of them have penetrated the root. Here, in the lowest 

 part of the cavity of the straw, they make preparations for pass- 

 ing the winter, and even for their escape from the straw the 

 t See F. M. Webster, Circular 117, Bureau of Entomology, U. S. Dept. Agr. 



