•204 HYMENOPTERA. 



whether it directly produces the galls, or is parasitic, like 

 many of the family, on other gall-insects. Dr. Harris, who has 

 studied the habits of the Joint-worm, states that the body of 

 the adult fly is jet black, and that the thighs, shanks (tibiae), 

 -and claw-joints, are blackish, while the knees and other joints 

 of the feet, are pale-3'ellow. Tlie females are .13 inch long, 

 while the males are smaller, have a club-shaped abdomen, and 

 the joints of the antemiiie siu-rounded with a verticil of hairs. 

 The larva is described by Harris from specimens received from 

 Virginia, as varying from one-tenth to nearly tliree-twentieths 

 of an inch in length. It is of a pale j^ellowish white color, 

 with an internal dusky streak, and is destitute of hairs. The 

 head is round and partially retractile, with a distinct pair of 

 jaws, and can be distinguished from the larvae of the dipterous 

 gall-flies by not having the v-shaped organs on the segment 

 succeeding the head. During the sum- 

 mer, according to Mr. Gourgas's observa- 

 tions reported by Dr. Harris, and when 

 the barley or wheat is about eight or ten 

 inches high, the presence of the young 

 Joint-worms is detected "b}' a sudden 

 Fig. 138. check in the growth of the plants, and 



the yellow color of their leaves," and several irregular gall- 

 like swellings between the second and third joints, or, accord- 

 ing to Dr. Fitch, "immediately above the lower joint in the 

 sheathing base of the leaf;" or, as Harris states, in the joint 

 itself. The ravages of this insect have been noticed in wheat 

 and barley. During November, in New England, the worms 

 transform into the pupa state, according to the observations of 

 Dr. A. Nichols, and "live through the winter unchanged in 

 the straw, many of them in the stubble in the field, while others 

 are carried away when the grain is harvested." In Virginia, 

 however, the larva does not transform until late in February, 

 or early in March, according to Mr. Glover. From early in 

 May, until the first week in July, the four-winged flies issue 

 from the galls in the dr^^ stubble, and are supposed to im- 

 mediately la}^ their eggs in the stalks of the young wheat or 

 barle}' plants. The losses b}^ this insect has amounted, in 

 Virginia, to over a third of the whole crop. The best remedy 



