The Joint Warm. 311 



lays several eggs in the outer sheath of the stalk, above the joints. 

 After they ha^ch, the worms commence feeding within the sheath, 

 and the constant irritation produced by them forms a woody gall, 

 or rather succession of galls, in the cavity of each of which lies a 

 small footless maggot, about the seventh or eighth of an inch in 

 length, having a "body with thirteen segments, and of a pale, 

 glossy, yellowish color. The number of worms in each cluster of 

 galls Varies from four to ten, or even more. The substance of the 

 stalk attacked becomes brittle, and either partially or entirely 

 fills its central cavity, and frequently distorts it into various irre- 

 gular shapes. I have often observed young rootlets putting out 

 immediately below a joint thus affected. The worms on the stalks 

 of wheat, when examined in February last, were yet in the larva, 

 but early in March several had assumed the pupa state. They 

 were about an eighth of an inch in length, of a pale yellow color, 

 which, as the pupae were near coming out, became afterwards 

 nearly black. These pupge had the rudiments of wings, legs, and 

 antennge, as in the perfect fly, but were motionless. Late in April 

 and the beginning of May, the flies made their appearance through 

 holes gnawed through the tough woody covering of the gall-like 

 excrescence in which they had passed the winter. This transfor- 

 mation, however, took place in a warm room. These flies are 

 about an eighth of an inch in length, of a black color, the knees, 

 joints, and feet, being tinged with yellow. The males, according 

 to Dr. Harris, vary'from the females by being smaller, and in 

 having no piercers. The joints of the antennae are likewise longer, 

 and surrounded with whorls of little hairs. The hind body is 

 shorter, less pointed at the extremity, and is connected with the 

 thorax by a longer stem. He also says that among fifteen females 

 only one male was found. This corresponds with what I have 

 observed, as out of sixty to eighty Joint Worm Flies, produced from 

 diseased stalks of wheat, I only procured one male, answering to 

 his description, and eight parasites not quite a tenth of an inch 

 in length, of a dark metallic shade, with yellow legs, and the an- 

 tennae much thicker at the end. These flies were furnished with 

 four transparent dotted wings. If the small insect figured in 

 the plate is the male, it is somewhat incomprehensible how it 

 happens that so many females appear at the same time without 

 more males. 



" Another four-winged fly also made its appearance from the 

 same stalks, of about an eighth of an inch in length, with an ab- 

 domen and legs of a bright yellow. The head and thorax were 

 of a dark color, and somewhat metallic lustre. The wings were 

 transparent, dotted, and fringed with short hairs, and the piercer 

 reached to the middle of the under part of the abdomen. 



" Dr. Harris states that it has been found in Massachusetts, that 

 ploughing in the stubble has no eftect upon the insects, which re- 

 main alive and uninjured under the slight covering of earth, and 

 easily make their way to the surface, when they have completed 

 their transformation. A free use of manure and thorough tillage, 



