The Spider Family Nesticidae (Araneae) in North America, Central America, and the West Indies

Gertsch, Willis

ABSTRACT: A systematic review of the spiders of the family Nesticidae from North America, Central America, and the West Indies is presented with analyses of their features and relationships. The sedentary nesticids spin small tangled webs in dark places beneath ground objects, in leaf and other detritus, in underground spaces, and especially in many parts of caves. Three genera and more than 50 species are now known from the area under consideration. The exclusively American genus Gaucelmus, with five species, ranges from our southeastern states and Texas southward through Mexico and much of Central America. Most Gaucelmus are cavernicoles, but only one species, cavernicola of Jamaica, is somewhat modified by cave existence. The worldwide genus Nesticus is strongly represented in North America where the distribution of its 40 species is disjunct. The European Nesticus cellulanus, introduced into North America by trade many years ago, occurs sparingly from New York to Maine and Nova Scotia. Two distinct species represent the West Indies, one from Cuba and the other from Hispaniola. The continental Nesticus occur in three widely separated enclaves: the southern Appalachian mountains, the Pacific Northwest, and eastern Mexico. A large and rich fauna of 24 species (representative of the rejected genus Ivesia) ranges in Appalachia from Kentucky and West Virginia through the parallel ranges into central Alabama. These form a distinctive series with specialized paracymbia and interesting tegular fragmentation of the male palpi. Most are cavernicoles, and some have the eyes reduced in size or obsolete: five of these, furtivus, barri, stygius, jonesi, and georgia, are claimed to be troglobites; four others, dilutus, valentinei, barrowsi, and holsingeri, also probably deserve this classification. This fauna of Appalachia was probably derived from a single basic stock that fragmented during the long history of the region. All the cavernicoles are allopatric, living in single caves or cave systems. The second center for endemic Nesticus in the United States is the coastal and Sierra Nevada area from...