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Cavernicolous Pselaphid Beetles of the United States

Orlando Park
The American Midland Naturalist
Vol. 64, No. 1 (Jul., 1960), pp. 66-104
DOI: 10.2307/2422894
Stable URL: http://www.jstor.org/stable/2422894
Page Count: 39
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Cavernicolous Pselaphid Beetles of the United States
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Abstract

There are thirty-three described species of cavernicolous Pselaphidae, divided among six genera, and three tribes. This fauna is separated to species in a series of taxonomic keys, and assembled in a checklist which includes original citation and type locality for each species. Described as new are Arianops stygica, Batrisodes gemmoides, B. ferulifer, B. jocuvestus, B. clypeospecus, B. pannosus, B. tumoris, B. krekeleri, B. schneiderensis, Bythinopsis hubrichti, Machaerites croceus, M. eurous, and M. steevesi. A fungus, near the ascomycete genus Stilbum, is reported from B. clypeospecus. Dimorphism has been found in the males of Batrisodes pannosus. The subgenus Batriasymmodes, formerly in the genus Batrisodes, is raised to full generic status, with monstrosus (LeConte, 1850) as its genotype. New combinations resulting from the above action include: B. troglodytes, B. spelaeus and B. quisnamus. Three synonyms are formed: Batrisodes jeanneli (Park, 1951), B. reduncus (Park, 1956) and B. quisnamus (Park, 1951) are synonyms of Batriasymmodes quisnamus. In Machaerites the subgenus Subterrochus is described as new, with ferus (Park, 1951) as type of subgenus. The probable role of small fissures from, or between caves is emphasized in the dispersal of cavernicolous pselaphids. Seven major drainage systems have been utilized by this fauna. Of thirty-three taxa only two are found in more than one of these drainage systems. Twenty-two of these taxa, or about 67 percent, occupy one cave per taxon. Exceptions to these two generalizations are discussed, with special attention to two species of Batriasymmodes. Only one case is known in which more than one species in a given subgenus occupies the same cave. As a background for a discussion of phylogenesis of cavernicolous pselaphids, their epigean allies are discussed briefly in terms of habitat niches occupied, response to illumination and moisture, feeding preferenda, and nocturnalism. Cave penetration and evolution of cavernicoles are discussed in terms of (1) chance occupancy, and (2) a known instance of colonization of a given cave by the epigean Batrisodes globosus. There appear to be three levels of structural modification. The first of these includes the genera Batrisodes, Batriasymmodes, and Bythinopsis. Each of these genera have both extant cavernicolous and epigean species. All of the cavernicolous populations are modified in that there is a reduction in the ocular facet number in one or both sexes. The second group shows greater structural modification. Eyes are absent and metathoracic wings are usually absent. There is a tendency for elongation of appendages, paler integuments, and loss or size reduction in foveae. Here belong Machaerites (subgenera Speleochus and Subterrochus) and Arianops (subgenus Arispeleops). These cavernicoles belong to genera or subgenera which do not have epigean representatives, that is, divergence is at the generic or subgeneric level. Finally, the tribe Speleobamini has an admixture of basic structural features found in both branches of the subfamily Pselaphinae, that is, divergence is at the tribal group level. Here belongs Speleobama vana in which eyes, wings, vertexal, pronotal, and elytral foveae are absent, appendages are long and integument pale.

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