A recapitulation of the Nearctic species of Centromerus Dahl (Araneida, Linyphiidae) with remarks on Tunagyna Debilis (Banks)

In any new region the knowledge of the spider fauna, or of any other group of organisms, has to go through three successive stages. In the beginning there is a period of descriptive activity with many new species recorded and named, in the past usually by several authors independently. In the Nearotic Region this stage may have ended for New England, but this is hardly true for the Far West and the southeastern part. In particular the names of Emerton, McCook, Keyserling, Banks, Petrunkevitch, Crosby, Bishop, Chamberlin, and Ivie, not to mention many others, are forever associated with this period. By building up large collections and giving their finds to the world they have laid the foundations of New World Arachnology. The second stage I would call the period devoted to regrouping and rearranging, and of summarizing local faunas. Older species have to be redescribed and furnished with illustrations. Many species have to be transferred to other genera, the genera have to be compared with those of other faunal regions. The following, third stage is that of the large revisions of smaller taxonomic units on a world-wide basis. North American arachnology, at least as regards the Linyphiidae, now seems to be in the second stage. Of course the stages outlined above are not sharply divided but grade into each other, and neither are all families on the same level. The Theridiidae are an example of a group that is much further advanced in this respect than most other groups. Ivie's work (1969) on Bathyphantes is a typical second stage revision. This paper on Centromerus is intended to function on that same second stage level. Centromerus was created by Dahl in 1886 for the reception of four