

[25] THE GRAPE-SEED FLY. 137 



interest of our country, and which, therefore, should be 

 promptly met and circumvented by all the means in our 

 power. 



The bunch of grapes, as received, contained a large number 

 of shriveled berries, upon which, as also upon nearly every 

 one of the perfect ones, could be seen with the naked eye, a 

 small round dot, in the center of which an elevated roughened 

 surface was visible with a magnifier. The dot marks the spot 

 where a very minute four-winged fly had punctured the skin 

 and deposited its egg. The egg hatching, the larva passes 

 through the pulp into one of the seeds, upon the kernel of 

 which it feeds, and within the empty case undergoes its trans- 

 formation to its pupal state, having previously provided for 

 the escape of the perfect fly by gnawing an aperture of suf- 

 ficient size in the seed. 



For the detection of this insect, for our knowledge of its 

 habits and transformations, and for its description, we are 

 indebted to Mr. W. Saunders, the able editor of the Canadian 

 Entomologist, who first observed the insect, in Canada, in the 

 fall of 1868. It was at first believed by him to be the larva of 

 a curculio, but subsequently was correctly referred by Prof. 

 Riley to the hymenopterous genus ISOSOMA. In the Canadian 

 Entomologist for November, 1869, it is described by Mr. 

 Saunders as Isosoma mtis. The fly is quite small, being 

 but about one- sixth of an inch in spread of wings ; its head, 

 thorax and abdomen are black, the wings clear and iridescent, 

 and the legs brown and black. The species is interesting from 

 its belonging to the same genus with the destructive joint- 

 worm fly, the Isosoma Tiordei (Harris), which has proved so 

 very destructive to the wheat, rye and barley crops ; and, 

 perhaps, even more interesting from a remarkable difference 

 in the sexes, pointed out by the late Mr. Walker of the British 

 Museum, "one of them representing the carnivorous EURY- 

 TOMA, and the other the herbivorous ISOSOMA, and thus one 

 species figuratively combines the diminishers of vegetation 

 and the controllers of such diminution." 



In an account of this insect Mr. Saunders says: "On the 

 20th of August, 1868, we observed that many of the berries in 

 the bunches of a Clinton vine, under our care, were shrivel- 

 ing up. On opening the grapes, we noticed that most of the 

 smaller berries that is, those which had shriveled earliest 

 contained only one seed, and that of an unusually large size ; 



