A newly published study in the Journal of Neurophysiology reveals how blow flies (Calliphora vicina)—despite their minimal body weight—reliably detect forces through specialized sensory organs in their legs. The research offers new insights into insect biomechanics and presents promising applications for the design of next-generation walking robots.

Researchers at Marshall University and West Virginia University examined the behavior of campaniform sensilla—strain-detecting sense organs in the fly’s hindleg tibia—and how they encode mechanical forces during posture and movement. Experiments showed that these sensors are highly sensitive not only to the magnitude of force but also to the rate at which it changes. Even very small, transient decreases in force strongly inhibited the sensors’ firing.

“Force sensing plays a crucial role in balance and locomotion,” said Sasha Zill, Ph.D., professor of biomedical sciences at the Marshall University Joan C. Edwards School of Medicine and lead author of the study. “Our findings show that even lightweight insects, such as blow flies, need to monitor both force magnitude and dynamics, and they do so in surprisingly sophisticated ways.”

The study found that campaniform sensilla in blow flies detect both the strength and rate of force application, with sensory responses showing hysteresis and sensitivity to even brief decreases in force. A mathematical model developed for larger insects accurately replicated these responses, supporting the idea that force detection is a universal, scalable strategy across species—one that aids in muscle control and balance and could inform the design of more stable, adaptable walking robots.

“This modeling approach could help us better understand sensory tuning across animals and improve robotic locomotion by mimicking how real sensory systems respond to force, bridging biological insight with practical engineering applications in biomechanics and robotics,” Zill said.

Additional authors on the study were Sumaiya Chaudhry and Hibba Chaudhry of the Marshall University Joan C. Edwards School of Medicine and Nicholas Szczecinski, Ph.D., of West Virginia University Department of Mechanical and Aerospace Engineering.