8 BULLETIlSr 432, U. S. DEPAETMENT OF AGEICULTTJRE. 



sap of the leaves upon which the adults subsist. Only a very small 

 proportion of the punctures are utilized as receptacles for eggs, 

 which fact would indicate that they are made for feeding purposes 

 rather than for oviposition. 



As a general rule, the punctures are made from the upper side, 

 in the tenderest portions of the leaves of recent growth. Sometimes, 

 however, punctures may be found even in the upper part of the 

 tender stems, especially in the case of young plants. 



The female adult of this species apparently first scars the leaf 

 surface with her ovipositor. Then, as the sap begins to escape from 

 this wound, the insect proceeds to feed and, with a rasping move- 

 ment of the mouth parts, digs little furrows between the leaf veins. 

 These feeding punctures are mostly in the form of furrows from 

 1 to 3 mm. in length and 0.5 mm. wide. Seven adults placed upon 

 young barley plants covered by a lamp chimney made 918 feeding 

 punctures in five days. All of these were on the upper surface of 

 the leaves. Another newly emerged female made 133 feeding 

 |)unctures on the upper leaf surfaces in a period of seven days. 



When leaves of yovmg plants are extensively punctured they pres- 

 ently begin to assume a pale yellow, sickly appearance, first at the 

 tips, but gradually extending down toward the base to the stem, 

 and finally they curl up and wither away. When more than one leaf 

 or if a majority of the leaves of the same plant are injured to this 

 degree by the punctures, the whole plant may die from the injury or 

 produce an inferior, worthless plant.' 



Older plants, as a rule, do not suffer from damage caused by 

 females puncturing the leaves, as they have considerably more leaf 

 surface and sufficient vitality to withstand the injury. 



INJURY TO PLANTS BY MINING HABITS OF LARV^. 



This species has been found to be most destructive in the larval 

 stage, mining in the leaves and sometimes in the stems of young 

 tender plants having only a limited area of leaf surface. Mines 

 started in the leaves of such young plants are often continued down 

 into the heart after reaching the base of the leaf to a point near or 

 slightly below the surface of the ground before the larvae reach ma- 

 turity and their ravages cease. The leaves arising from the bud hav- 

 ing been severed, they dry up, and the whole plant presents an 

 appearance as though infested with the wheat bulb-worm {Meromyza 

 americana Fitch) or some species of the genus Oscinis. 



Young tender oat plants about 3 inches tall, having from three to 

 four leaves, were found by the senior author to be injured in this 

 manner in a small patch of oats at Columbia, S. C, in the fall of 1914. 



The larvae of C. dorsalis have been observed by the junior author 

 causing much injury to small barley plants in the fields in several 



