INSECT-GALLS OF THE VICINITY OF NEW YORK CITY 23 



46. Lettuce Tumor Gall (Aulax tumidiis Bass.). — Varies greatly in shape 

 and size from a slight, knotty and irregular enlargement of the stalk to a large 

 and more or less ovate swelling, 2 to 3 in. long and i in. in diameter. Inside 

 it is pithy and filled with many cells. Found on the main stalk of wild lettuce 

 {Lactuca canadensis) , usually near the summit, often in the panicle itself, and 

 then covered with the short flower stems. Common. 



Family Tenthredinid.« (Saw-flies). 



With few exceptions the members of this family do not 

 produce galls, the larvae being leaf-eaters. The larvse very 

 much resemble the caterpillars of butterflies and moths, but 

 they have, ordinarily, from 12-16 prolegs, while true cater- 

 pillars have as a rule only 10. The adult female is furnished 

 with a pair of saws at the end of the abdomen which she uses 

 to make slits in the leaves and stems of plants in which she 

 places her eggs. 



47. Willow Apple Gall {Ncmatus ponium Walsh). — Rounded and fleshy, 

 somewhat resembling a miniature apple. Yellowish green, usually with a 

 rosy cheek. Measures about i in. in diameter. On leaves of bush ■willow. 

 July and August. Rather common. 



