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634 NEW YORK STATE MUSEUM 



operations in the vicinity of Albany. It probably causes very little or 

 no injury. 



Poplar twig gall fly 



Agromyza aeneiventris Fallen 

 This little fly, kindly identified by Professor Coquillett through the 

 courtesy of Dr Howard, produces oval, smooth swellings about y 2 inch long 

 on one side of small poplar twigs [pi. 50, fig. 3]. It is rather abundant at 

 Karner, the insects wintering within the galls as larvae, adults appearing in 

 early spring. 



Description. The parent insect is a small, black fly, with red eyes, less 

 than y% inch long. 



The larva is a greenish yellow maggot about y% inch long with strongly 

 tridentate jet-black mandibles, as shown in figure 170, and 

 with a pair of spiracles borne on knobbed elevations at each 

 extremity of the body. 

 Fig. 170 Larval mandi- The pupariuiTi is oval, less than y% inch long, each seg- 



ble of Agromyza 



aeneiven tris, ment with an irregular, slightly wavy, transverse series of 

 much enlarged (orig- 

 in 1 ) chitinous points near its anterior margin. Posterior extrem- 

 ity terminated by a pair of stout, blunt, slightly moniliform processes. 



Life history. The young larva apparently begins operations in the 

 green bark, causing an irritation which results in the rapid development of 

 abnormal tissues, producing a spongy, oval mass on one side of the twig — 

 probably hypertrophied bast. These galls vary considerably in size, rang- 

 ing from about 3/g inch in length to compound masses about an inch long. 

 The smaller galls contain a single larva while the larger ones may be 

 inhabited by several. The gall tissue is very soft, almost cheesy in texture, 

 very different from the ordinary wood fiber. This is true of the majority 

 of the galls found in the spring, which occur on last year's growth. A few 

 are found on growth of the preceding year, and these are remarkable for 

 containing oval, hard masses of woody tissue a little less than y% inch 

 long. The galls, in older tissues, usually contain several maggots. The 

 larvae make rather broad, short galleries about an inch long in a portion 



