108 



4- Low Prairie Association 



The moist black soil prairie, a degree removed from the wet or 

 swamp condition, with ground water in the spring relatively near the 

 surface, is fairly well characterized by the rosin-weed (Silphium), par- 

 ticularly S. terebinthinaceum. Other plants likely to be associate^ with 

 5*. terebinthinaceum are Silphium laciniatum and S. integrifolium, 

 Bryngium yuccifolium, Lepachys pinnata, and, to a less degree, Lac- 

 tuca canadensis. 



In the Charleston area this condition is represented by Station I, a, 

 north of the town, and Station III, a, and in part b, east of the town. 

 The proximity of ground water is shown at Station I, e^ by the pres-, 

 ence of crawfish burrows, probably those of Cambarus gracilis. At 

 Station III the proximity of water was also evident where S. terebin- 

 thinaceum was most abundant in the railway ditches. Such perennial 

 plants are indicative of the physical conditions for a period of years, 

 and are thus a fairly reliable index of average conditions — much more 

 so than the annuals. 



It is difficult to decide which kinds of animals are characteristic of 

 this kind of prairie. Provisionally I am inclined to consider the fol- 

 lowing as being so : Cambarus gracilis; Argiope aurantia; the grass- 

 hoppers Bncoptolophus sordidus, Melanoplus differentials , M. femur- 

 rubrum, Scudderia texensis, and Xiphidium strictum; CBcanthus nigri- 

 cornis; Phymata fasciata; and asilids. The presence of Lepachys was 

 clearly an important factor in determining the presence of Melissodes 

 obliqua and Epeolus concolor. At Station III, b, east of Charleston, 

 Hpicauta pennsylvanica and Bombus pennsylvanicus, auricomus, and 

 impatiens were taken on the flowers of Silphium terebinthinaceum. 



Robertson ('94, pp. 463-464; '96b, pp 176-177) has pubHshed lists 

 of insect visitors to the flowers of Silphium and Lepachys ('94, pp. 

 468-469), at Carlinville, 111. Recently Shelf ord ('13a, p. 298) has 

 published a long list of animals inhabiting Silphium prairie near Chi- 

 cago. Forbes ('90, p. 75) has reported the snout-beetle Rhynchites 

 hirtus Fabr. as feeding upon Silphium integrifolium. 



In a colony of prairie vegetation at Seymour, 111., which included 

 much Silphium and Bryngium, the following insects were taken Octo- 

 ber 7 from the ball-like flower clusters of Bryngium yuccifolium: the 

 bugs Lyg(2us kalmii, Thyanta custator Fabr., Bu^chistus variolarius, 

 and Trichopepla semivittata Say (No. 539, C. C. A.), the last named 

 in large numbers, the nymphs in several sizes as well as the adults, a 

 fact which suggests that both may hibernate upon the prairie. Rob- 

 ertson ('89, pp. 455-456) has summarized his collections of insects 

 from Bryngium and on Buphorbia corollata ('96a, pp. 74-75). 



