The use of spatial cues for structural guideline orientation inTapinoma sessile andCamponotus pennsylvanicus (Hymenoptera: Formicidae)

Camponotus pennsylvanicus(DeGeer) and Tapinoma sessile(Say) exploit structural elements as guide-lines in their topographic orientation. This research documents the response of T. sessileand C. pennsylvanicusto a series of thigmotactic, gravitational, chemotactic, and phototactic cues while utilizing structural guidelines. Adherence to these guidelines is more pronounced on vertical than on horizontal surfaces and more pronounced in darkness than in daylight. Orientation switches from a crestline on the horizontal to a groove on the vertical. Light and odor trails serve an important role as distance cues in structural guideline orientation. The hierarchy of orientation cues and the adaptive significance of these ant's exploitation of structural guidelines are discussed.