Taxonomy, Natural History, and Zoogeography of the Rainbow Snake, Farancia erytrogramma (Palisot de Beauvois)

Abstract

The rainbow snake has been listed generally as Abastor erythrogrammus (Latreille), 1802. However, on zoological grounds genus Abastor Gray, 1849, must be synonymized with Farancia Gray, 1842. The original spelling of specific name, erytrogrammus, al- though etymologically poor, was not an inadvertent error, and should not be emended to erythrogrammus. The author of name ery- trogrammus was not Latreille but Palisot de Beauvois, whose Memoire sur les Serpents was inserted in Sonnini and Latreille's Histoire Naturelle des Reptiles. This work dates from 1801, not 1802. The rainbow snake should therefore stand as Farancia erytrogramma (Palisot de Beauvois), 1801; type locality l'Amerique septentrionale, restricted by Harper, 1940, to the lower Cooper River, in vicinity of Charles- ton, S. C. A later restriction of type locality to Alachua County, Florida, is unacceptable. Two subspecies are recognized. Farancia e. erytrogramma ranges from extreme southeastern Louisiana and central Mississippi eastward into northern Florida, and thence northward through Atlantic Coastal Plain to extreme southern Maryland. F. e. seminola, new sub- species, is known only from Glades County, Florida, its range being disjunct from that of F. e. erytrogramma by more than 150 miles. Two saltwater populations of F. e. erytrogramma have been found, indi- viduals thereof differing in color from inland specimens. Farancia e. erytrogramma is ecologically separated from sympatric F. a. abacura, former inhabiting alkaline (calcareous) to circum- neutral streams, latter frequenting acidic streams, ponds, and bogs. F. erytrogramma, as an adult, feeds almost entirely upon common eel, Anguilla rostrata, while adult F. abacura prey upon eel-like sala- manders, Siren and Amphiuma. Farancia e. erytrogramma lives in submerged roots of bald-cypress trees or beneath submerged man-made structures. In north-central Florida, specimens are most active in March, June, and October; but species is fairly active all year in that area, and peaks of activity are not high as compared with those of most terrestrial snakes. Nests, eggs, and thermal relations of rainbow snake are described. Known enemies include indigo snake (Drymarchon), hawks, and commercial collectors. There is sexual dimorphism not only in ventral and subcaudal counts, but also in ventral spotting. Females exceed males in maximum size. The South American snake, Pseudoeryx plicatilis (Linnaeus), is similar to Farancia in many anatomical features as well as in habits. The similarity reflects relationship, not parallelism. Both genera are thought to have been derived from a Mexican ancestor, now extinct. The distribution of Farancia-like snakes, as well as speciation and subspeciation within Farancia, are largely explicable in terms of Pliocene and Pleistocene geology and climate.