BLACK GRAIN-STEM SAWFLY. 11 



In the case of one male specimen reared from wheat stubble by 

 McConnell, the insect was collected as a larva September 30, 1915, 

 and emerged as an adult May 3, 1917. This shows that under some 

 conditions the life cycle may be extended over a two-year period. 

 Such instances are probably rare under natural conditions, but the 

 record indicates a high degree of adaptability on the part of the 

 species for overcoming unfavorable conditions. 



EXTENT AND CHARACTER OF INJURY. 



Shortly after receipt of the complaint from Gaithersburg, and be- 

 fore the identity of the insect was known, the writer was detailed to 

 visit the locality and investigate the nature and extent of the damage. 

 Accordingly, on July 22, 1918, the farm of the correspondent, Mr. 

 Beverly R. Codwise, was visited. It lies about 3 miles north of 

 Gaithersburg on the road to Laytonsville, Md. Unfortunately the 

 infested fields had already been harvested, making it practically im- 

 possible to estimate the extent of the actual injury. It was evident, 

 however, that there had been an appreciable loss due to falling of the 

 grain, so that it could not be picked up by the binder. The writer 

 was informed that comment by passers-by on the large amount of 

 grain missed by the binder had first called attention to the injury 

 and caused the investigation which resulted in the sending of samples 

 to the Bureau of Entomology. 



Three other farms in the neighborhood of Gaithersburg were 

 visited, on each of which the pest was located. Subsequently wheat 

 fields in various other localities in Maryland and one in Virginia were 

 visited, with the result that in every wheat field examined the insect 

 was found to be present in varying abundance. 



No actual counts of infested straw were made by the writer in any 

 of the fields to ascertain the percentage of infestation. It was roughly 

 estimated that in some of the worst cases the infestation amounted to 

 4 or 5 per cent. In most of the fields the infestation was much less 

 than 4 per cent. Messrs. McConnell and Myers did make counts 

 of the infested stubble on a small number of experimental plats and 

 other fields of wheat at Carlisle and Mount Holly Springs, Pa., 

 with the results showing an infestation varying from 4.36 per cent 

 on one of the plats to 0.26 per cent on another, the average from all 

 counts being 1.75 per cent. 



That a 4 per cent infestation of stubble necessarily indicates a 4 

 per cent loss in the crop is not probable. The insect apparently 

 chooses only well-developed and vigorous stems in which to oviposit, 

 and some of these infested stems are known to develop at least par- 

 tially filled heads. Just what the loss, if any, from failure of the 

 heads on infested stalks to fill properly may be, remains to be de- 

 termined. 



