The rear fangs of these snakes are large for the size of the snake. Various collectors have been bitten, and several reports of the effect of the poison have been published. The snakes are aggressive and bite constantly while being handled. A field companion, Dale L. Hoyt, was bitten on the forefinger by a specimen of C. l. lineatus and immediately felt a burning sensation. The finger swelled, much as it would if stung by a wasp, but it returned to normal size in about twenty-four hours. Ditmars (1931:legend pl. 27) reported immediate burning pain and a localized swelling, an inch in diameter and half an inch high, which lasted for several hours. Mertens (1952b:83) reported merely that the hand of the gardener at the Instituto Tropical in San Salvador bled strongly for a full hour. Edward H. Taylor was bitten by a specimen of Conophis vittatus (Taylor and Smith, 1939:252); pain and swelling lasted for some time. Taylor (personal communication) is still troubled by damage incurred by that bite, which apparently resulted in mechanical damage to the second joint of the middle finger, for the joint swells when the finger is used or exercised. William E. Duellman (personal communication) was bitten on the hand in July, 1956. There was immediate pain and localized swelling, both of which disappeared several hours later.
TAXONOMIC RELATIONSHIPS AND EVOLUTION
The genus Conophis is known only from the Recent. Except that Conophis belongs to the subfamily xenodontinae and probably is of New World origin, little is known about the relationships of the genus. Auffenberg (1958) described a new genus and species of fossil colubrid snake from the Miocene of Montana as Dryinoides oxyrhachis and compared it with several recent genera. This specimen, of which there is a relatively complete skull and a series of vertebrae, seems most closely to resemble a specimen of Conophis lineatus dunni (UF 7657) from Honduras, with which it was compared in basic osteology. The two genera could be related, for the progenitors of Conophis possibly inhabited much of North America in the Miocene.
Another possibility is that the main stock of the xenodontines reached South America in earliest Tertiary times, and that the formation of the Panamanian and Colombian seaways that separated South America and Central America from the Late Paleocene to the middle of the Pliocene left the Conophis stock isolated in Middle America where members of the genus dispersed through semi-arid habitats.
Turning our attention now to the species within the genus, instead of the genus as a whole, Conophis vittatus is readily set apart from other members of the genus on the basis of the universal presence of seven supralabials. In basic coloration it also differs, having no stripe on the 1st scale-row, or spots on the venter, and a maximum of four broad stripes on the body. The other species appear to be more closely related; these make up the C. lineatus-group. Conophis nevermanni differs so much from the other species that it might be placed in a separate group. Nevertheless, the basic striped pattern, which is masked by the increased melanism of many specimens, indicates that nevermanni is more closely related to the lineatus-group than to vittatus. The lineatus-group, thus, consists of pulcher, nevermanni and the three subspecies of lineatus. In this group the color pattern is characterized by the high frequency of ventral spotting, darkening of part of the supralabials, dark pigmentation on the 1st scale-row, and more than four dark stripes on the body of adults. Conophis lineatus concolor, on which the dark pigmentation on the body apparently is secondarily lost, is an exception.
If differences in color pattern be used as an indication of the relationships between the species and subspecies of the genus Conophis, I would consider C. vittatus the most divergent unit. The subspecies of lineatus closely resemble one another and, as a unit, resemble pulcher from which they differ primarily in the position of the dorsalmost stripes. Conophis nevermanni is more divergent than is pulcher from the species lineatus, but probably is not so far removed from lineatus as is vittatus.
In the light of what has been pointed out immediately above with respect to resemblances of, and differences between, the species, an hypothesis to account for their formation and for their presence in the areas where they are today is the following: Concurrent with climatic fluctuations in the Late Pliocene and Pleistocene, the northernmost population differentiated into the species vittatus, and has subsequently spread north and west from the region of Tehuantepec, México. During the same period nevermanni became isolated in northern Costa Rica.
The species pulcher probably differentiated from the remaining lineatus stock during the Early Pleistocene orogenic upheaval in Guatemala. The pulcher stock was isolated on the Pacific Coastal slopes of Guatemala, while lineatus moved through the subhumid corridor of northern Middle America into México and southward toward Costa Rica (Stuart, 1954a). In the Late Pleistocene and Recent, pulcher moved back across the central Guatemalan highlands occupying its present range in northern Middle America. Primarily because of the formation of unsuitable habitat (wet forest) that presently separates the geographic ranges of populations of lineatus, this species differentiated into three subspecies.