107 



3- Swamp-grass Association 



The prairie swamp-grasses, slough grass (Spartina), and wild rye 

 (Elymus) were growing in relatively pure stands or colonies in de- 

 pressions which were dry in the late summer. The prolonged wetness 

 of the habitat and the dominance of the few kinds of grasses are char- 

 acteristic features of the environment of this association. These con- 

 ditions were found at Station I, a and c, north of Charleston. As these 

 stations were rather homogeneous and have already been discussed 

 somewhat fully, only a summary will be given here. 



On account of the grassy vegetation the abundance of Orthoptera 

 is not surprising. Representative species are Melanoplus differen- 

 tialis, M. femur-rubrum, Scudderia texensis, Orchelimum vtilgare, 

 Xiphidium strictum, CBcanthus nigricornis, and (B. quadripunctatus. 

 Other representative animals are Argiope aurantia and the swamp fly 

 Tetanocera plumosa. The list of species is probably very incomplete ; 

 during the wet season there are undoubtedly a number of aquatics ; 

 furthermore, there are still other species which feed upon Spartina and 

 Blymus, particularly some Hemiptera, and stem-inhabiting Hymenop- 

 tera, and certain Diptera. Thus Webster ('03a, pp. 10-13, 26, 32, 38) 

 has recorded a number of chalcids of the genus Isosoma which live 

 in the stems of Blymus virginicus and canadensis. In this same paper 

 he discusses their parasitic and predaceous enemies (pp. 22, 27, 33). 

 A fly also breeds in Blymus, the greater wheat stem-maggot, Mer- 

 omyza americana Fitch (PI. XX, figs. 1-5), as recorded by Fletcher 

 (1. c, p. 48). This species is of economic importance,. having spread 

 from grasses to the cultivated grains. It has been studied in Illinois 

 by Forbes ('84). He found a fly parasite of this species, and Webster 

 reports a mite preying on it. Webster (1. c, p. 53) reports another 

 fly, Oscinis carbonaria Loew, bred from Blymus by Fletcher. 



In another paper Webster ('03b) has published a list of insects in- 

 habiting the stems of B. canadensis and virginicus. Osborn and Ball 

 ('97b, pp. 619, 622; '97a) have discussed the Hfe histories of certain 

 grass-feeding Jassidce which feed upon Blymus. Osborn ('92, p. 129) 

 records a plant-louse, Myzocallis, from Blymus canadensis in Iowa, 

 and a species of leaf -hopper has been recorded by Osborn and Ball 

 ('97b, p. 61 5') from Spartina. On the same plant, Osborn and Sirrine 

 ('94, p. 897) record a plant-louse on the roots. In a list of the plant- 

 lice of the world and their food plants Patch ('12) lists a few from 

 Spartina. This same list includes (pp. 191-206) many grasses and 

 the associated aphids, those on Blymus on page 196. 



