A virtual robot to model the use of regenerated legs in a web-building spider

The garden cross orb-spider, Araneus diadematus, shows behavioural response s to leg loss and regeneration that are reflected in the geometry of the we b's capture spiral. We created a virtual spider robot that mimicked the web construction behaviour of thus handicapped real spiders. We used this appr oach to test the correctness and consistency of hypotheses about orb web co nstruction. The behaviour of our virtual robot was implemented in a rule-ba sed system supervising behaviour patterns that communicated with the robot' s sensors and motors. By building the typical web of a nonhandicapped spide r our first model failed and led to new observations on real spiders. We re alized that in addition to leg position, leg posture could also be of impor tance. The implementation of this new hypothesis greatly improved the resul ts of our simulation of a handicapped spider. Now simulated webs, like the real webs of handicapped spiders, had significantly more gaps in successive spiral turns compared with webs of nonhandicapped spiders. Moreover, webs built by the improved virtual spiders intercepted prey as well as the digit ized real webs. However, the main factors that affected web interception fr equency were prey size, size of capture area and individual variance; havin g a regenerated leg, surprisingly, was relatively unimportant for this trai t. (C) 1999 The Association for the Study of Animal Behaviour.