REPORT OF THE ENTOMOLOGIST. 



387 



This field was harvested on July 11, being cut the usual height from 

 the ground, and on the next day I examined 90 harvested straws and 

 found in them 25 larva?. This, I think, gives a fair idea of the percent 

 age of larvae the farmer removes from the field in the straw. 



By a careful examination of the sheaves I found that, while the first 

 joints were almost invariably removed with the grain, comparatively 

 few of those of the second were included, the straw having in the ma- 

 jority of cases been severed between the two. 



In this way, larvoe between the first and second joints, or in the lat- 

 ter, were at once placed largely at the mercy of numerous carnivorous 

 foes, from whom they had previously been secure. The larva?, in the 

 majority of cases, where they had not already ensconced themselves in 

 the soft walls of the inside of the straw, as they sometimes do, had 

 burrowed down into the joint and lay awaiting the time when they were 

 to pupate. They vary considerably in size, large and small being pro- 

 miscuously distributed throughout the straw. 



Parasites. — There are at least six of these which have to a consider- 

 able extent reduced the Isosoma larv;e in point of numbers. Two of the 

 most efficient in this work are Hymenoptera (Stictonotu? isosomatis Riley, 

 and Eupelmus allynii French), which deposit their eggs in the infested 

 straws in June, and by September 10 the young larvae have hatched, 

 de stroyed their victims, transformed to the adult and escaped from 

 the straw. As soon as the grain is harvested the larvae thus exposed, 

 as previously explained, are rapidly depleted in numbers by two other 

 foes. 



One of these is the larva of a Carabid, Leptotrachelus dorsalis Fab., a . 

 slender, somewhat depressed larva 8 mm in length, which descends into 

 the stubble aud devours both the Isosoma larva and that of the Hymen- 

 opterous parasite, should it chance to be there. 



When full grown it stops the aperture by which it entered with a 

 pellet, constructed from bits of the interior substance of the stubble, 

 which it tears off with its jaws, and in a short time enters the pupa 

 stage, transforming to the adult a few days later. 



Curiously enough, during the time it occupies the stubble in the 

 larva and pupa stages it sometimes falls a victim to the second of these 

 t wo parasites, viz., the mite Heteropus ventricosus Newport, which enters 

 the 3tubble ostensibly for the same purpose, but whose sense of dis- 

 crimination is rather poorly developed, and, although infinitely the 

 smaller of the three, is finally victorious over the Isosoma larva, its 

 parasite, and their mutual enemy, the leptotrachelus larva. 



This mite, whose habits I have studied before,* is a very convenient 

 parasite, and will make its way where the others would fail, if there is 

 the minutest avenue by which it can reach its victim. I shall refer to 

 it again farther on. 



WHEAT AND GRASS SAW-FLY. 

 (Family Tenthredinidce.) 



My acquaintance with this insect has so far been confined to the 

 larva? only, having first found it in that stage in considerable abund 

 ance on the 14th of May. 



They were at this time feeding on the leaves of wheat in a field near 

 Bloomington, 111. At first I thought they came from a piece of woods 



* See Twelfth Report of State Entomologist of Illinois, pp. 144-154. Bound in the 

 Trans. Depart, of Agriculture of Illinois, Vol. XX, 1880. 



