. Animal communities in temperate America : as illustrated in the Chicago region; a study in animal ecology. Animal ecology; Zoology -- Illinois Chicago. COTTONWOOD ASSOCIATION 225 d) Tree stratum.—The cottonwood is attacked by many borers. The most characteristic is Pledrodera scalator, which is not common. There are few leaf-feeders excepting two gall aphids; the petiole gall is due to the work of Pemphigus populicaulis, and the terminal gall to Pemphigus vagabundus (137). These occur on the cottonwoods along the lake rarely, being more abundant farther inland, where they are protected from
. Animal communities in temperate America : as illustrated in the Chicago region; a study in animal ecology. Animal ecology; Zoology -- Illinois Chicago. COTTONWOOD ASSOCIATION 225 d) Tree stratum.—The cottonwood is attacked by many borers. The most characteristic is Pledrodera scalator, which is not common. There are few leaf-feeders excepting two gall aphids; the petiole gall is due to the work of Pemphigus populicaulis, and the terminal gall to Pemphigus vagabundus (137). These occur on the cottonwoods along the lake rarely, being more abundant farther inland, where they are protected from the severity of winter. The osprey nests in trees, and the tree-swallow in the dead ones. We have noted that this association often arises through the burying of the preceding one. Deposition of sand is the chief cause of succession up to this point. When cottonwoods and grasses begin to grow and digger- wasps begin to burrow, organic mat- ter is continually added to the soil. The grasses die down from time to time, the roots and leaves of the shrubs and other plants add humus. The myriads of digger-wasps which go elsewhere (probably commonly to the beach) for the animals with which to store their nests add a large amount of organic matter at a depth of a few inches. The grasses bind the dune sand; the conditions become favorable for other plants, stage the bunch-grass and seedlings of pines Fig. 189.—The long-horned locust (Psinidia fenestralis) (after Lugger). At such a 4. TRANSITION BELT (Station 58; Table L) (Fig. 190) (115, 170) The stage of mixed pine seedlings, old cottonwoods, and the begin- ning of the bunch-grass constitutes a well-marked belt. Along the shore, from Indiana Harbor to Gary, there was formerly a ridge upon which the lakeward-facing side supported the typical community of the cottonwoods and the landward side the transitional belt. When one crosses to the landward side of such a ridge he notes a change in the animals. The white tiger-beetles
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Keywords: ., bookcentury1900, bookcollectionbiodive, booksubjectanimalecology
