THE 



VOL. 1. 



ST. LOUIS, MO., APRIL, 1869. 



NO. 8. 



CIjc ^merkatt ^ninmokgbt. 



PUBLISHED MONTHLY BY 

 F. STXJXJX.E'Sr &; CO. 



104 OLIVE STREET. ST. LOTTIS. 



TERMS One dollar per annum in advance. 



EDITORS : 



BENJ. D. WALSH Eock Island, lU. 



CHAS. V. UILEY, 21.30 Clark Ave St. Louis, Mo. 



THE JOINT-WORM. 



(Isosoma /lordri, Harris.) 



Its Oiierations upon small Grain. 



In certain years and in particular States the 

 crops of wheat, of barley, or of rye are ob- 

 served to be greatly injiirecl by a minute mag- 

 got, popularly known as the "Joint-worm." 

 This maggot is but little more than one-eighth 

 of an inch long, and of a pale yellow color with 

 the exception of the jaws, which are dark 

 brown. It inhabits a litlle cell, which is situa- 

 ted in the internal substance of the stem of 

 the affected plant, usually a short distance above 

 the first or second knot from the root, the outer 

 surface of the stem being elevated in a corres- 

 ponding elongate blister-like swelling; and 

 when, as is generally the case, from three to 

 ten of these cells lie close together in the same 

 spot, the whole forms a woody enlargement 

 "honey-combed by cells, and is in reality a many- 

 celled or "polythalamous" gall, analogous in 

 its nature and structure to those which we have 

 described in a preceding article. (No. G of the 

 Amek. Entom.) In Figure 113, a, will be seen 

 a .sketch of one of these galls, the little pin- 

 holes being the orifices through which the flies 

 produced from the joint-worms have escaped. 

 At first sight, these knotty swellings of the 

 stem are apt to elude observation, because, 

 being almost always situated just above the 

 joint or knot on that stem— whence comes the 

 popular name "Joint- worms'" — they are en- 

 wrapped and hidden by the sheath of the blade ; 

 but on stripping off the sheath, as is supposed 



[Fig. ll:i ] 



Colors— (o) stniw-yL-Uow; (ti) blark 



to have been done in tlie engraving, they be- 

 come at once very conspicuous objects. We 

 have observed that the " internodes,"' as bota- 

 nists call them, or the spaces between the knots, 

 in infested straws are always much contracted 

 in length, none out of a lot of over lif'ty speci- 

 mens examined by ns exceeding six inches in 

 length, and many being reduced to only one and 

 a half inches. A similar phenomenon occurs iu 

 two "polythalamous"' galls formed by certain 

 Gall-gnats {Cecidomyia) upon the tips of the 

 twigs of certain species of AV^illow.* There 

 were only three straws in this lot of over fifty 

 sti'aws, where two Joint-worm galls were found 

 in the same straw; and in all those three cases 

 they were found in two adjoining internodes. 

 In a very few instances the galls were situated 

 in the middle of the internode, or even close to 

 the upper knot, instead of being situated as 

 usual immediately above tlie lower knot. 



Amonnt of Damage done by the .luint-worin. 



The damage occasioned by the Joint-worm is. 

 in certain seasons and in certain localities, 

 ruinously great. In the year 1851, throughout 

 a large part of Virginia, according to the Editor 

 of the Southern Planter, " many crops of wheat 

 were hardly worth cutting on account of its 



•The Willow Wheat-gall {Salicis MHcoides, Walsh) and 

 the Willow Barley-gall (Salicis hordeoides, Walsh), growing 

 respectively on the Heart-leaved Willow (S, corddta) and 

 the Humble Willow (S. humilin) , and described in Proc. 

 Ent. Soc. Philad. IU, pp. 598-9. They received these n,-une» 

 from their resemblance respectively to ears of wheat and 

 barley. 



