1920] ECONOMIC ZOOLOOY — ENTOMOLOGY. 363 



Black grain-stem sawfly of Kuropo in the United States, A. P>. O.vhan 

 (f. S. l)ci)t. Ai/r. liul. H.lJi (11)20), pp. i<S. pin. 2, fifl. /). — Tliis is a report urxm 

 Trachclus tnbidiis (Fab.), another exotic insect of considerable importance 

 which has become established in the United States, The fact that it is now quite 

 widely distributed in this country and is becoming a source of injury has led 

 to the publication at this time of such information as is at liaiid. 



This insect, which occurs in most of the countries of Europe and is of consider- 

 able economic importance, was first collected in this country at Riverttm, N. J., 

 some time prior to 1800, but it was not recof^iiized as a Euroi)ean species tiiitil 

 about 1010. Injury caused by it to wheat at CJermantown, Rid., was reporteil by 

 Corey in 1014 under the name of Crphus pinnnwus L. CVmiiilaints of injury to 

 wheat at Gaithersburg, Rid., received by the Bureau of Entomolojxy in lOlS, led 

 to the investigations by the autlior here reported. The records at hand are 

 said to be sufhcient to establish a probability that it already occurs over the 

 greater part of Virginia, Maryland, Pennsylvania, New .Tersey, and Delaware, 

 and it is possible that West Virginia, eastern Ohio, soutliern New York, and 

 even some of the New England States may J)e included within its i-ange. 



Thus far in America only wheat and rye are known to serve as food plants, 

 but a number of others have been recorded in Europe. There are, as yet, only 

 two instances of its occurrence in rye in this country, and in each case only 

 single stalks in a field. 



The only species occuring in America, so far as known, witli which this species 

 is likely to be confused are ('. ciiictu.'< Norton and C. pi/(/in<ru)i L. The larvfc 

 of the three species are apt to be confused, since all three infest the small grain 

 crops in practically the same manner, have similar biologies, and superticially 

 re.semble one another closely. A table is given by means of which the larv:e of 

 the 3 species may be separated. 



Observations indicate that its life history does not differ greatly from that of 

 the western grass stem sawfly (C. cinrtus), although the early stages have not 

 yet been observed in this country. Collections of adults in the field indicate 

 tliat egg-laying take« place from May 1.") to .Tune 10. The eggs are inserted in 

 a slit made by the female in the stein some distance above the ground. The 

 young larvje burrow downward thrcmgh the pith of the .stem, hollowing it out 

 to the base. They attain full growth about the time the grain is ripe, growth 

 having been completed at the time investigations were commenced on .July 22, 

 and the larvfe having at that time apparently entered hibernation. At that 

 time the hibernating larva was found at the extreme base of the stem of the 

 wheat stalk. Before the burrow is completely closed, the stem is almost com- 

 pletely severed from the inside, at or near the surface of the gromid. As a 

 result, the first bending of the ripened straw, as by a strong wind, causes it 

 to snap off and fall. 



The hibernating period apparently extends from the time the wheat is ripe 

 enough to cut until sometime the following .spring when the larva changes to 

 the piipa. Just when this change takes place has not been ascertained, but the 

 pujtal state is probably of short duration, as in the case of C. cinctiis. The 

 adults are found in the fields during the latter half of May a.ul early .Tune. 

 The injury results in the falling of a large amount of grain which is missed 

 by the binder. It was roughly estimated that in .some of the worst cases 

 the infestation amounted to 4 or .5 per cent, although in most of the fields the 

 Infestation was less than 4 per cent. C<tunts made by McConnell jind RIyors of 

 infested stubble in experimental plats and wheat fields at Carlisle and RIount 

 Holly Springs, Pa., showed variations from 4.3() per cent on one plat to 0.2(5 

 per cent <m another, the average from all counts beinu' 1.7.' per cent. One effi- 



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