A SAW-FLY BORER IN WHEAT. 



CEPHUS PYGMAEUS. 



Order HYMENOPTERA ; Family TENTHREDINIDAE. 



AN insect destructive to wheat, but previously unknown in this 

 - country, has appeared in considerable numbers on the Cor- 

 nell Universit}^ Farm. I do not know of its occurrence anywhere 

 else in this State ; but as it is extremely abundant here, it is doubt- 

 less spread over a considerable area. It was first observed in this 

 locality two years ago, by one of our students, the late Mr. S. H. 

 Grossman, while making an investigation of wheat insects. Mr, 

 Grossman's studies, however, were sadly terminated before he had 

 carried his investigations of this species very far ; and it has fal- 

 len to me to continue the work begun b}' him. 



On examining the stalks of wheat at harvest time by splitting 

 them throughout their length, it was found that some of them had 

 been tunnelled by an insect larva. This larva had eaten a pas- 

 sage through each of the joints so that it could pass freely from 

 one end of the cavity of the straw to the other. In addition to 

 tunnelling the joints they had also fed more or less on the inner 

 surface of the straw between the joints ; and, scattered throughout 

 the entire length of the cavity of the straw, except the smaller 

 part near the head, were to be seen yellowish particles, the excre- 

 ment of the insect. 



If infested straws be examined 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 \ inch (5 mm.) to ^ inch (12 mm.) in 

 length. The smaller ones may not have bored through a single 

 joint ; while the larger ones will have tunnelled all of them, ex- 

 cept, perhaps, the one next to the ground.* 



As the grain becomes ripe the larva works its way toward the 

 ground ; and at the time of the harvest the greater number of them 

 have penetrated to the root.f Here in the lowest part of the cavity 



*For a detailed description of this larva see note 2. 

 fFor further details see note 4. 



