The Orb-Weaving Spiders of the Chicago Area

Abstract

The spiders of the southern shores of Lake Michigan and vicinity have not been treated as a unit although Banks (1905), Elliott (1932) and others h-ave included parts of this area in lists of spiders of surrounding states. From 1932 to 1942, the author collected in the Chicago area (roughly including the drainages of the Illinois and Fox rivers) on more than 125 field trips, eacl of which averaged about one day in extent. As a result, over 300 species have been identified within about 50 miles of Chicago. Future papers will present the results of this collecting. The forty-one species of ecribellate orbweavers found in the area are included in three families-Epeiridae, Tetragnathidae, Theridiosomatide--all formerly included in the Argiopidae (or Epeiridae). The present annotated list is represented largely by specimens in the author's collection, but also inctudes specimens in the collections of the Chicago Natural History Museum, the Chicago Academy of Sciences, Northwestern University as well as some in the private collections of Drs. Sewall Wright, Robert E. Gregg and Mrs. Elizabeth Moffatt. The Chicago area may be considered a typical mid-western area with all types of habitats of such an area represented. Most conspicuous and unique is the Indiana-Michigan Sand Dunes area with its interesting series of biological communities. Various climax forest regions, prairies, flood plains, streams, lakes, tamarack bogs, and transitional areas are well represented. Most of the records in this paper are from material whose identification is certain and do not include the immature specimens which are difficult to determine. I have not examined the collections of Mrs. Moffatt but have included information of this worker from her unpublished manuscript on the spiders of the Chicago area written in 1925. Since the death of Mrs. Moffatt the location of her collection is unknown and verification of her species is impossible. However, since many of them are easily recognized from the accompanying photographs, and since many of them were personally checked by J. H. Emerton, and also since no species recorded in her paper is absent from the author's collection, it is reasonable to assume that their determination was valid. This paper is organized to serve not only as a check list but also as a key for identifying species found in the area. Therefore, it is recommended that anyone attempting to use the key should either be familiar with the use of spider keys or have access to Comstock's Spider Book, McCook's American Spiders and their Spinning Work, or Kaston's Spiders of Connecticut. Any one of these references has good discussions of key characters and most of the species concerned, though Kaston's book probably would be found to be the most useful.