2 QO 



PRAIRIE COMMUNITIES 



usual leader of the clan. On the great plains these united 

 and formed the larger herds of 20,000 to 4,000,000 or more, 

 which have been described by travelers. The males aided 

 in defending the young. The cowbird is said to have fol- 

 lowed the herds constantly. 



b) Field stratum. The lepidopterous larvae are similar 

 to those of the low prairie, but much less numer- 

 ous. The hymenoptera are represented by Bom- 

 bus separatus, and many of those recorded on the 

 low prairie. The adult of the parasite (Tiphia 

 mdgaris) of the May-beetle larva 

 (Figs. 296-97) occurs commonly. 

 Several species of aphids (Figs. 

 298-300) occur, especially on the 



milkweeds and thistles. 

 These are commonly at- 

 tended by ants, which 

 stroke them and secure the honey dew from 

 the posterior ends of their alimentary canals. 

 The aphids reprcduce rapidly, the young being 

 born in rapid succession at a very ad- 

 vanced state of development. They 

 begin sucking the juices of the plant 

 at once. Several small parasitic 

 hymenoptera (braconids) (Fig. 

 299) lay their eggs in the bodies 

 of the aphids. These finally kill 

 the aphids, whose bodies with 



FIG. 298. A viviparous grain louse (Macrosiphum granaria Kirby) with her 

 newly born young on a barley leaf (after Washburn, Bull. 108, Minn. Agr. Exp. Sta., 

 Fig. 2, p. 262). 



