Waters, J.S. & McGlynn, T.P.

Natural history observations and kinematics of strobing in Australian strobe ants, Opisthopsis haddoni (Hymenoptera: Formicidae)

The strobe ants of Australia (Opisthopsis spp.) move with a rapid staccato gait, appearing as if they are under a strobe light. This extraordinary behavior has long caught the attention of natural historians, but the mechanics of strobing locomotion are as enigmatic as its function. We used high-speed video to track the movements of strobing Opisthopsis haddoni eMery, 1893 and O. haddoni rufonigra Forel, 1910 ants to develop plausible explanations for the phenomenon. We found that strobing involves periodic bursts of rapid acceleration and deceleration. The ants engage in walking with an alternating tripod gait, punctuated by pauses, with a strobing cycle frequency of 5 - 7 Hz. While stopped, ants distinctly tap their antennae on the ground and raise them again before resuming their gait. The peak speeds of strobe ants, at 50 - 60 body lengths per second, are impressive but are only sustained for an infinitesimally short period of time, and overall average speeds are slower due to the prolonged pauses between strobe cycles. We posit that strobing behavior may have evolved as a form of camouflage to move without easy detection or as a tradeoff to maximize high-speed locomotory behavior within the constraints imposed by the spatial and temporal demands for neurosensory processing.