PROC. BIOL. SOC. WASH. 102(3), 1989, pp. 651-697 ON THE CRAYFISH GENUS FALLICAMBARUS (DECAPODA: CAMBARIDAE) IN ARKANSAS, WITH NOTES ON THE FODIENS COMPLEX AND DESCRIPTIONS OF TWO NEW SPECIES Horton H. Hobbs, Jr. and Henry W. Robison Abstract.— The genus Fallicambarus, embracing 16 species of burrowing crayfishes, is represented in Arkansas by eight of them, five of which are mem-bers of the nominate subgenus and three assigned to the subgenus Creaserinus. A key is provided for the identification of the 16, the combined ranges of which extend from Ontario to southwestern Texas and southwestern Georgia, and from South Carolina to Maryland. Fallicambarus (F.) petilicarpus, a close rel-ative of F. (F.) dissitus, is described from Union County, Arkansas, and F. (C.) gilpini, related to F. (C) caesius, from Jefferson County, Arkansas. Data are presented for placing Fallicambarus (C) uhleri (Faxon) and F. (C.) hedgpethi (Hobbs) in the synonymy of F. (C.) fodiens (Cottle). For each of the species occurring in Arkansas, as a complete a synonymy as possible is offered along with a diagnosis of the species; also included are a statement of the range, a list of localities (also noted on spot maps) and specimens examined, color notes, size ranges of adults, and life history and ecological notes. Among the more interesting and least known of the crayfishes of Arkansas are eight species assigned to the genus Fallicambarus. Like all of their congeners, those occurring in Arkansas are seldom found in permanent bodies of water, and, as adults, only after rains or during floods do they frequent tem-porary pools or runoff. Throughout most of their lives, these crayfishes inhabit burrows that are excavated in areas where, for most of the year, the water table does not drop more than a meter or so beneath the surface (in Arkansas, such areas exposed to the sun often may be recognized by the presence of hydrophilic sedges). Turrets, sometimes in the form of slender chimneys, but more often irregular mounds of earthen pellets of a size proportional to that of the crayfish, mark the scattered burrows which, in many areas, may be seen in, or adjacent to, roadside ditches. Less frequently, clusters of mounds, or even entire fields studded with turrets signify the presence of large colonies of these crayfishes. Although seldom seen during daylight hours, on warm evenings individuals, with chelipeds extended, may be observed at the mouths of their lairs, sometimes perched at the top of a chimney, or, when the humidity is sufficiently high, and particularly follow-ing a shower, walking over the ground. Dur-ing the early spring and after rains, evidence of the presence of a crayfish in its domocile is provided by damp-to-wet pellets of soil recently deposited at openings to the bur-rows. Such signs of recent excavation are seen most frequently early in the day, before the pellets have become dry, but, if the weather is overcast, recent deposits may be found at almost any hour. At one time or another, there exist for most burrows constructed by members of the genus Fallicambarus more than one opening at the surface that lead into the sim-
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