258 MANUAL OF VEGETABLE-GARDEN INSECTS 



a liberal quantity of copper sulfate solution. Less injury will 

 result to the plants if the water is drained off soon after the 

 cress has been gathered. 



Reference 



U. S. Bur. Ent. Bull. 66, pp. 11-15. 1907. 



The water-cress leaf-beetle, Phoidon aruginosa Suffrian 



In the eastern United States water-cress is occasionally in- 

 jured by the larvae and adults of a small shining, bronzy black 

 leaf-beetle about ^ inch in length. The life history of this 

 insect is very imperfectly known. The full-grown larva is 

 about i inch in length ; the head is shining black and the re- 

 mainder of the body is brownish black, lighter between the 

 segments and below. Its body is provided with numerous 

 prominent tubercles from which hairs arise. Both larvae and 

 adults feed on the underside of the leaves. 



No satisfactory method of controlling this pest has been 



devised. 



Other water-cress insects 



Diamond-back moth : 12 



Spinach aphis : 105 



Striped cabbage flea-beetle : 324 



Lettuce 



The most important insect enemies of lettuce are the cab- 

 bage looper, the celery looper and several species of cutworms. 

 Several kinds of plant-lice infest the plants and are especially 

 troublesome in greenhouses. Slugs and millipedes often at- 

 tack the crop, sometimes causing considerable damage. 



The lettuce root-louse, Rhizohiiis lactuca; Fitch 



The roots of lettuce are often infested by a yellowish wing- 

 less plant-louse about yV i^ich in length which has the body 



