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I was always wondering if brains all these spiders and flies have the capability to reconstruct the surroundings in 3D like mammals do, or their sophisticated eyes are only light and motions sensors. Observing e.g. fly evading flyswatter which resembles random walk, it's likely the latter.

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Their eyes are not going to have evolved past the point of providing any incremental benefit, and a fly is after all a simple critter who's main concern is finding a pile of shit to eat, and avoid being swatted by a cow's tail. I'd guess their eyes (& visual system) are perhaps better regarded as crude visual sensor rather than anything much like the visual system of an animal that benefits from recognizing whether that shitty ass belongs to a cow vs a tiger.

In general it may be the latter. Portia spiders in particular, though, will observe a target, observe their surroundings, then navigate a complex path around and through structures that block their vision of the target to reach a destination that will allow them to attack it. Suggesting very much that they form some kind of model of their surroundings, plan a path through it, and remember that path.

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