12 BULLETIN 834, U. S. DEPARTMENT OF AGRICULTURE. 



It is certain that serious loss may and does occur because of fall- 

 ing of the grain due to the cut made by the larva preparatory to 

 hibernation. The extent of this loss will in all probability depend 

 in some degree upon weather conditions during the period of ripening 

 of the grain. A heavy wind or severe storm at this time would cause 

 most of the infested grain stalks to break off and fall so that they 

 would not be picked up by the harvester. In the absence of such 

 a wind or storm, the loss would undoubtedly be much less, but even 

 with favorable conditions a certain percentage of the infested stalks 

 would be broken off by the harvester reel and fall in front of the plat- 

 form. 



Kulagin (47) states that losses in Russia due to this species and 

 Cephus pygmaeus are estimated at 14 to 20 per cent, although more 

 severe in some cases. Shtchegolev (49) also reports 15 to 20 per 

 cent injury due to these two pests. Other Russian writers record 

 severe injury without specifying the amount. Unfortunately, in 

 practically every instance these writers treat of the injury by 

 Cephus pygmaeus and Trachelus tabidus collectively, without indi- 

 cating how much of the damage is chargeable to each. This is no 

 doubt due to the fact that they have been unable to distinguish the 

 larvae of the two species. Their records, therefore, do not afford 

 a reliable basis for estimating the probable future importance of 

 Trachelus tabidus in this country. 



PARASITES. 



In Russia two parasites of Trachelus tabidus have been recorded. 

 Collyria caleitrator (Gravenhorst), an ichneumonid wasp, is ap- 

 parently a common parasite of this species as well as of Cephus 

 pygmaeus. Borodin (52) records the chalcidid Arthrolysis {Picro- 

 cystus) scabricula Nees as having been reared from these two saw- 

 fly pests. Neither of these species has, as yet, been found in America. 



The existence of at least one efficient parasite in America has, 

 however, been established. Numerous specimens of a chalcidoid 

 belonging to the genus Pleurotropis and apparently representing an 

 undescribed species have been reared by Mr. W. R. McConnell at 

 Mount Holly Springs and Carlisle, Pa. So far little is known of the 

 life history of the species. It emerges from the prepupal larva of the 

 Trachelus at about the time of emergence of the host adults and is 

 believed to be a primary parasite, solitary in its habit. Observations 

 to date are too limited in extent to form a very accurate estimate 

 of the efficiency of this parasite, but in some instances at least it 

 appears to exercise a considerable degree of control. 



SUGGESTIONS FOR CONTROL. 



In the present state of our knowledge of this species only sug- 

 gestions of possible means of control can be given. 



