REPORT OF THE ENTOMOLOGIST. 539 



Then a simple emulsion of soap in proportion of 1 to 4 was made with the oil and 

 finally abandoned, not being effective against the worms when reduced so as not to 

 iniure the plants. , ,- , '..i. m •„ 



Li"-hter oils of the same character were resorted to and apphed with a spray. 1 ins 

 killed the vermin, yet injured the plant. Still lighter oils were used, but, when 

 spraved on, the foUage was materially injured. A vaporizer by means of compressed 

 air was substituted for the sprav, and witli use of very Uglit oil or naptha, known m 

 commerce as 88, in half a second froze the worm and plant aUke, with tins diiier- 

 euce, that in ten or fifteen mmutes the vermin revived, but the tender leaves and 

 twigs wilted and hirned black as though struck by Jack Frost m January. 



The grade of oil was reduced imtil the proper gravity of, say, 77 was found to kill 

 the vermin and still leave the plant essentially unharmed. 



The mechanical devices for vaporizing the oil and applying it to the upper branches 

 of trees and shrubbery alike, as demonstrated to the Commissioners of the Distrjct 

 some time since, and to wliich you kindly refer, have been since perfected, and so 

 retluced in cost as to make the management easy by any common day laborer and 

 the whole cost within the reach of all interested, whilst the oil costs less than 10 

 cents per gallon. 



JOINT "WORMS. 



Order Hymenoptera ; Family Chalcidid^. 



THE COMMON JOINT WORM. 



{Isosoma hordei, Harr.) 



This old and well-known species lias for the past few years been 

 increasing in numbers and importance in certain sections of the coun- 

 try, while for a number of years previously it had been almost lost 

 sight of. Since 1881 its work has been quite noticeable in portions 

 of Louisa, Albemarle, Goochland, Orange, and Fluvanna Counties, 

 Virginia, or, in other words, in just the locality where it was observed 

 and studied thirty-five years ago by F. G. Ruffin, Professor Cabell, 

 and Mr. Rives. Through the courtesy of Mr. F. C. Brooke, of Cuckoo, 

 Louisa County, we have been kept informed of the progress of the 

 pest and have been supplied with specimens from time to time. 



In June, 1885, wishing to learn definitely the state of affairs in this 

 section, and more particularly on Mr. Brooke's farm, we sent one of our 

 assistants, Mr, Pergande, accompanied by Mr. A. Stewart, a member 

 of the Entomological Society of Washington, to Cuckoo to make a 

 few days' observations. The reports made by these gentlemen showed 

 that the damage done to the wheat crop by this and other wheat in- 

 sects was very great. Mr. Brooke's croj) for 1884 averaged less than 

 5 bushels to the acre, which did not pay expenses. 



The Joint Worm was not alone concerned in accomplishing this 

 result, although an important factor. The Hessian Fly {Cecidomijia 

 destructor), the Wheat Midge (Diplosis tritici), the Wheat Isosoma 

 {Isosoma tritici), the Tarnished Plant-bug {Lygus lineolaris), and 

 quite a number of other hemipterous insects were present in^ force, 

 and almost every straw had been injured by one or more of these 

 species. In the portions of the field most injured the plants were 

 often scarcely a foot in height, few in number, and many were bent 

 near the ground, so that frequently six or eight out of a bunch of 

 twelve were prostrate. The ears of these straws were, however, bet- 

 ter developed and fuller of sound grain than those which stood erect. 

 On examination the prostrate stalks were found to be badly infested 

 by Joint Worms above the first or second joint, but almost entirely 

 free from Hessian Fly and Wheat Midge, while the standing stalks 



