A Tibial Gland Scent-Trail and Trail-Laying Behavior in the AntCrematogaster AshmeadiMayr
Psyche: A Journal of Entomology
IN2"RODUC'I'ION Wasmann (I899) speculated that ants might lay odor trails by using: their feet. But with the exception of a challenge by Brun (I914) the footprint hypothesis was laid dormant. In all ant species thus far analysed, trail-substances originate from the ga.ster of the ant, whether the instrument is the sting, as in the Myrmicinae, the anus, as in the stingless Ponerinae, Dorylinae and Formicinae, or the posterior border of the sixth abdominal sternite as in Dolichoderina.e (Wilson
... oderina.e (Wilson I963, Gabba 967). The myrmicine ant, Crematogaster ashmeadi, obviously builds up scent trails for communication. However, the gasters of workers are never seen to touch the substrate, not even when a new trail is being established. The workers often erect the abdomen upward and, especially when excited, they even bend it forward superimposed to the thorax so that they take on the superficial appearance of a little spider rather than an ant. Their sting is often protruded, but it never touches the. ground. Goetsch (934) observed the peculiarity of the trail-laying o.f the Mediterranean species Crematogaster scutellaris. He also noticed that they never touch the substrate with their abdomen. He describes the behavior of trail-laying workers as the t:ollowing: "The ant performs a kind of dancing step folding its hindlegs". He suspected the pheromone source to be somewhere in the gaster and claimed that the trail substance is possibly released as a vapor, the hindlegs functioning to support the gaster at a fixed heig:ht above the ground. The described behavior is compatible with my observations, in (7. ashmeadi, but our interpretations differ greatly. The dancing step of the hindlegs, in fact, is a description of trail-laying by footprints. It will now be shown that a physMogically functional system of trail-laying has evolved in C. ashmeadi that involves the hindlegs, a system which early naturalists were thinking about without having seen it.