These robots have a neural network, which is modeled after the nervous systems of silkworm moths. The robot can search for the pheromone and trace its flow to reach the odor source like a real silkworm moth.

References :
Sumito Nagasawa, Ryohei Kanzaki, Isao Shimoyama, “An Evaluation Method for Insect Sensorimotor Models Using an Insect-Size Mobile Robot,” 2001 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS '01), pp. 551-556, Hawaii, USA, Oct. 29-Nov. 3, 2001. [Proceedings]

Ryohei Kanzaki, Sumito Nagasawa,Isao Shimoyama, “Neural Basis of Odor-Source Searching Behavior in Insect Brain Systems Evaluated with a Mobile Robot,” Chemical Senses, vol. 30, Suppl. 1, pp. i285-i286, 2005. [Paper]