Ability of the Blind Snake, Leptotyphlops dulcis, to Follow Pheromone Trails of Army Ants, Neiv amyrmex nigrescens and N. opacithorax

Abstract

On three occasions blind snakes were observed crawling in nocturnal raiding columns of N. nigrescens without feeding on the ants or their prey.2 Neither snakes nor ants seemed disturbed, although a fourth snake following a vacated ant trail was attacked when placed in a raiding column. The latter snake and one of those found in raiding columns (assumed conditioned), along with a blind snake found unassociated with ants (assumed unconditioned), were tested on N. nigrescens and N. opacithorax pheromone and distilled water trails in the laboratory. Conditioned snakes followed the pheromone trails in a significant number of experiments; the unconditioned snake did not. Head-neck rearing, thought to be olfactory orientation behavior, was observed in trail following. Because blind snakes smell army ant trails, are known to feed on ant brood, and were heading toward army ant nests in half the field observations, pheromone trail following may be selectively advantageous for the snakes in locating a large food supply at the ant nest site. Blind snakes (Leptotyphlops dulcis) are primarily fossorial but sometimes crawl or secrete themselves on the ground surface, especial- ly during nights of favorable temperature-moisture conditions (Burt, 1935; McCoy, 1960). They feed on ant eggs, larvae, pupae, and ter- mites which they locate by olfactory cues (Gehlbach, unpublished observ.; Reid and Lott, 1963). Although army ants of the genus Neivamyrmex (Formicidae, Dorylinae) are largely subterranean in nesting habits, workers of N. nigrescens often extend raiding columns more than 50 m along the ground surface in search of the brood of other ants. During such forays and colony migrations, the ants orient themselves by depositing and following pheromone trails (Schneirla,