r. S. 1). A.. L;. !•:. r.iil. CC. I'ail II. IssikmI April L':;. I'.MIT. 



SOME INSECTS INMl'KiOUS TO TRUCK CROPS. 



THE WATER-CRESS SOWBUG. 



{ MoiicdscUiis liraclijiHiiis Wwv^vv.) 



During tlie past tlirt>e years this isopod has attracted very consid- 

 erable attention because of its occurrence in troublesome numbers in 

 water cress {Nasturtium officinale) grown for market in poi'tions of 

 Virginia, West Virginia, and Pennsylvania. The species is purely 

 aquatic, thus differing from our connnon dooryard sowbugs, Avliich, 

 although most abundant in moist locations, are strictly terrestrial. It 

 belongs to an entirely different family, tlie Asellidie. Avhich contains 

 three genera, mostly fresh-Avater forms, inhabitants of streams, Avells, 

 pools, and lakes. 



DESCRIPTIVE. 



This species is so distinct from the more connnon sowbugs (Onis- 

 cidse) that a brief description will suffice. Its general appearance 

 is shown, dorsal view, in figure '1 The body is much depressed, and 

 the legs are long and strong. Seen from the side, it is decidedly 

 shrimplike. The peculiar structure of the antenme may be noticed 

 in the illustration. They terminate in long flagella, composed of 

 many joints. When mature this sowbug attains a length of 13 or 14 

 millimeters, or a little upward of half an inch, and is a little more 

 than twice as long as wide, and gray in color. This creature is not an 

 insect, but a crustacean, and therefore classed with crayfish and crabs. 

 A detailed description is given by Miss Kichardson," who briefly men- 

 tions McKees Spring, Gaylord, and Le.xington. Va., as localities 

 Avhere this sowbug was " reported injurious to water cress." 



By recent correspondence we have obtained necessary information 

 in regard to the habits and manner of operation of this sowbug, and 

 we have also been successful in ascertaining what promises to be a 

 very perfect remedy for the pest in its occurrenc-e in streams and in 

 spring water. It appears to aifect cress only below the surface of the 

 water, attacking the roots and lower leaves, and cutting off the stems 



1 Mouogvaph of the Isopnds of Nortli Ainorica. K.v Harriet Richanlson. Kul. 

 54. U. S. Xatioual :Museiun. Wasliintrton. I'.Xjr.. \^\\ 4n-4VJ, fis-s. 4<;()-4(;i. 



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