— 133 — 



with heads from stalks of average size will not indicate the results 

 of the presence of the insect. Still, as I have already said, it ap- 

 pears that with us the chief injur)^ caused by the insect is the 

 lodging of the grain. 



Some observations were made to determine how abundant this 

 insect is at Ithaca. It was found that the proportion of straws 

 infested varied from y^y- of one per cent to ii per cent., with an 

 average of 4^% per cent.* 



It is stated by European writers that this Saw-fly infests both 

 wheat and rye. I had no opportunity to studj' the last named 

 grain, but made some observations to determine the range of food- 

 plants of the insect here. There was a field of oats on the Uni- 

 versity Farm adjoining a clover field tliat w^as in wheat last year. 

 These oats were sowed very earlj' so that at the time the Saw-flies 

 were ovipositing the stalks were large enough to receive the eggs. 

 I found Saw-flies on the plants ; but a careful examination of a 

 large number of oat straws made at harvest time, failed to reveal 

 a single infested straw. 



I confined fifty Saw-flies, thirty males, and twenty females, in a 

 cage with growing orchard grass, which was large enough to re- 

 ceive the eggs. In a short time the females began to oviposit 

 freely in the grass ; but although many eggs were laid in the 

 grass, I was unable later to find a single larva, or any indications 

 of their having fed upon the interior of the stalk. Neither could 

 larvae be found in orchard grass growing in a field where there w^as 

 wheat last j^ear. 



Curtis describes a parasite that infests this Saw-fly in England. 

 It is the Ichneumon -fly, Pachyment^ calcitrator. But although I 

 have bred many hundreds of the Saw-fly and have examined 

 thousands of infested straws, in only two instances have I found 

 any indications of parasites. f We nnist, therefore, depend on ar- 

 tificial means for checking the increase of tliis species. 



The most obvious method of combating the insect is to attack 

 it while it is in the stubble, that is to say, sometime between the 

 wheat harvest and the first of the following May. If the stubble 

 can be burned in the autumn the larvae in it can be destro3-ed. 

 The same thing could be accomplished by ploughing the stubble 

 under, which would prevent the escape of the adult flies. But as 

 it is customary in this region to sow grass seed with wheat I fear 



* See note 6. f See note 8. 



