TRUE PRAIRIE 275 



leaves of the Andropogons. The meadow grasshopper {Orchelimum 

 vulgare [Harris]) lays its eggs in the stems of subdominant forbs, 

 especially composites (Hancock, 1911; cf. Hebard, 1934). 



An abundance of Hemiptera characterizes the true prairie; many 

 of these suck the juices of plants and may seriously weaken them. 

 The plant bug {Adelphocoris rapidus Say) is common in the various 

 grassland habitats of Illinois and Iowa and with it are about 15 other 

 common species. Some of these are predatory ; the ambush bug [Phy- 

 mata erosa fasciata Gray) is common on forbs, often found lurking in 

 goldenrod. The sucking Hemiptera may impair the vigor of grasses, 

 as is illustrated by the ravages of chinchbugs, which are claimed by 

 many to be original inhabitants of the true prairie. Upwards of a 

 dozen species of Orthoptera are found in true prairie in considerable 

 numbers, Melanoplus dawsoni Scud, occurring from Alberta south to 

 Missouri. 



The Coleoptera of the grassland include such forms as the so-called 

 cucumber beetle {Diabrotica 12-punctata Fabr.) and various others 

 that feed on forbs, decaying material or excrement {Aphodius distinc- 

 tus INIull.), or are predatory, as the lady beetle {Hippodamia conver- 

 gcns Guer) . However, the common and abundant species do not ordi- 

 narily feed directly on the grasses. Lepidoptera are more or less 

 abundant, but in general are not grass feeders, though significant in 

 the pollination of many subdominants. The extended studies of Hen- 

 drickson (1930) showed that only one species {Cercyonis alope olym- 

 pus Edw.) was found persistently in the Iowa prairies. 



Diptera are always abundant, but their relations are little known. 

 Notable among them are the long-legged flies, several species of the 

 genus Dolicopus being common or abundant. Syrphus flies, whose 

 larvae feed on aphids, and robber flies such as Asilus and Promachus, 

 abound; the latter prey on flying insects, picking them up with great 

 dexterity and often taking forms larger than themselves. Hendrickson 

 found them most abundant in an Andropogon community. 



The Hymenoptera are represented chiefly by the ants, which con- 

 stitute important coactors by gathering both plant and animal food, 

 and also produce important reactions in moving soil. In Hendrickson's 

 study the species were found to differ sharply with changes in the 

 grasses present. Halictus, Bombus, and Andrena are usually the abun- 

 dant bees of grassland. Thysanura and Collembola occur in prairie 

 soil and work on decaying vegetation. Earthworms are usually abun- 

 dant; the small white forms are nearly always present, as are small 

 zonitid and pupid snails of minute size. Both enter into the food of 

 birds, and the snails sometimes serve as carriers of bird parasites. 



