104 



from the surrounding slopes. At the same time, burrowing animals, 

 particularly the crawfish, also bury debris and work over the soil. In 

 the Charleston area this community was developed at Station I, d, and 

 in part at I, g. 



The representative animals of this community are those living in 

 the water, such as the prairie crawfish, Cambanis gracilis (PI. 

 XXXVI), the snail Galba iimhilicata, and such insects as the nine- 

 spot dragon-fly, Lihelliila pnlchclla (PI. XXXVIII, fig. 2), and the 

 giant mosquito, Psorophora ciliata, whose immature stages are spent 

 in the water. In addition to these are other representative species 

 whose presence is, to an important degree, conditioned by the pres- 

 ence of certain kinds of vegetation — such species, for example, as 

 those which feed upon the dogbane (Apocynum), the brilliantly col- 

 ored beetle Chrysochus auratns; upon milkweed, the milkweed bugs 

 Lyg(Tus kalmii and Oncopelhis fasciatus (PI. XL, figs, i and 3), and 

 the milkweed beetle Tetraopcs; and, finally, the rather varied series of 

 flower visitors feeding upon pollen or nectar, such as the soldier-beetle 

 (Chaitliognatlms pennsyhanicus), Euphoria sepiilchralis, and several 

 species of butterflies, moths, bees and wasps, including the honey-bee, 

 bumblebees, and carpenter-bee (Xylocopa zirginica) , and the common 

 rusty digger-wasp (C Morion ichneiimoneiim) . Visiting the same flow- 

 ers, but of predaceous habit, were found the ambush spider (Misuviena 

 aleatoria) and the ambush bug (Phymata fascia ta). Small insects 

 were preyed upon by the dragon-flies (Lihcllula pulchclla) , and the 

 dragon-flies in turn were entangled in the webs of the garden spider 

 (Argiope aurantia). 



No animals were taken on the flags, but Needham ('00) has made 

 an important study of the population inhabitating flags at Lake Forest, 

 Illinois, and shows that it is an extensive one. He gives an excellent 

 example showing how the injury by one insect paves the way for a 

 train or succession of others. For example : the ortalid fly Chcctopsis 

 anea Wied. (PI. XVIII, fig. i), bores into the stem of the buds and 

 causes them to decay (Cf. Forbes, '05, p. 164; Walton, Ent. News, 

 Vol. 19. p. 298. 1908). This condition affords a favorable habitat for 

 a pomace-fly (DrosopJiila plialerata Meig.*), an oscinid (Oscinis 

 coxcndix Fitch, Plate XVIII, figures 3 and 4), a beetle, parasitic 

 Hymenoptera, and, after the decaying buds were overgrown by fungus 

 threads, the bibionid fly Scatopse pulicaria Loew. This paper by Need- 

 ham is one of the very few in which the population of a plant has been 

 studied as a biotic community. Forbes ('90, pp. 68-69; 02» P- 444) 

 has shown that snout-beetles (Sphenophorus ochreiis Lee, Plate 



*Mr. J. E. Mallocli informs me that D. phalerata is not an American species. 



