Sensorimotor transformations underlying spider web-making

The geometric complexity and stereotypy of spider webs have long generated interest in their algorithmic origin. Web-making is especially amenable to comprehensive modeling because both the input and output of this behavior consist of the web itself, which can be specified completely in terms of its geometry. However, quantitative analyses have been sparse due to the difficulty of recording web-making in real-time. In recent computational work, we demonstrated that the stages of this behavior are generated by distinct and stereotyped motor sequences, but the sensorimotor and internal state mechanisms that generate these observed sequences remain unknown. Here, we present an assay and algorithms for real-time tracking of limb movements and web structure produced by the orb-weaver Uloborus diversus. We capture tactile interactions between spider and web and identify sensory cues triggering motor actions. Due to the conjugate relationship between leg movements and web geometry, these sensorimotor rules can be reanalyzed in terms of the effect their accompanying geometrical transformations have on web fitness. With parallel efforts in our group to establish calcium imaging in this small spider, it may offer a tractable model for the study of complex and likely cognitive behaviors.