SWAMP FOREST COMMUNITIES 191 



and others) and under the loosened bark are centipedes (Lithobius), milli- 

 pedes (Polydesmus), and beetle larvae (Pyrochroidae) which are flattened. 



While we have no actual records of mammals in such situations, 

 doubtless the varying hare (Lepus americanus Erx.) which frequents 

 marshy woods with thickets such as the buttonbush, the common shrew, 

 which nests under logs, and the mink (Mustela vison lutreocephala Harlan), 

 all have been visitors if not residents in such situations in the past. The 

 wood-duck, the woodcock, and prothonotary warbler often nest in such 

 woods. 



Field stratum: The field stratum is inhabited by small flies, such 

 as crane-flies, midges, and mosquitoes (Chironomidae and Culicidae), 

 occasional spiders, such as Theridium frondeum, parasitic hymenoptera 

 (Pimpla inquisitor Say, Ichneumon mendax Cress.) and the scorpion-fly 

 (Panorpa), which breeds in the ground. 



Shrub stratum : The shrubs consist chiefly of buttonbushes and low- 

 hanging grapevines. The vines frequently have conspicuous insect 

 galls. One called the grapevine apple gall, because of its shape, is due 

 to the larva of a small fly (Cecidomyia vitis-pomum W and R) (137); 

 another which is a pointed tube on the leaf is due to Cecidomyia viticola. 

 Wartlike galls on the under side of the leaves are due to Phylloxera 

 vastratrix PL (Fig. 277, p. 273) (150), an aphid which, when introduced 

 into France, threatened to destroy the vine industry. These occur only 

 on the vines on high ground where the roots, upon which a part of the 

 life of the aphids is spent, are out of water. Several grape insects, includ- 

 ing the fulgorid bug (Ormenis pruinosa Say), have been taken. 



Tree stratum: The tree stratum of this girdle has not been studied, 

 because the study of the tree stratum in general is difficult. The white 

 ash is, however, attacked by many insects. Felt (137) and Packard (154) 

 record a number. One of the most difficult groups to secure is the 

 " borers" of the solid wood or sapwood of trunk and twigs. These are 

 chiefly beetle larvae, especially the Cerambycidae (155), or long-hprned 

 beetles. The larvae of these are legless and only slightly larger at the 

 anterior end. Another prominent family is the metallic wood-borers or 

 Buprestidae (155). The larvae of these are also legless and may be dis- 

 tinguished from the preceding by a broad, flattened enlargement just 

 behind the head. The ecology of these two families alone is a subject 

 for a work the size of this volume (see 137 and 154). The four-marked 

 borer (Eburia quadrigeminata Say) is said to occur on the ash through- 

 out Indiana (156). The elm and basswood likewise have many borers, 

 some in common with the ash. 



