Flies and other insects use incoherent motion (parallax) to the front and sides to measure distances and identify obstacles during translation. Although additional depth information could be drawn from below, there is no experimental proof that they use it. The finding that blowflies encode motion disparities in their ventral visual fields suggests this may be an important region for depth information. We used a virtual flight arena to measure fruit fly responses to optic flow. The stimuli appeared below (n = 51) or above the fly (n = 44), at different speeds, with or without parallax cues. Dorsal parallax does not affect responses, and similar motion disparities in rotation have no effect anywhere in the visual field. But responses to strong ventral sideslip (206° s-1) change drastically depending on the presence or absence of parallax. Ventral parallax could help resolve ambiguities in cluttered motion fields, and enhance corrective responses to nearby objects.

中文翻译：

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腹侧运动视差可增强果蝇转向视觉侧滑的能力。

苍蝇和其他昆虫使用前后不连贯的运动（视差）来测量距离并在平移过程中识别障碍物。尽管可以从下面得出其他深度信息，但是没有实验证明它们在使用它。蝇类在其腹侧视野中编码运动差异的发现表明，这可能是深度信息的重要区域。我们使用虚拟飞行场来测量果蝇对光流的响应。在有或没有视差提示的情况下，刺激以不同的速度出现在下方（n = 51）或上方（n = 44）。背面视差不影响响应，并且类似的旋转运动视差在视野中的任何位置均不起作用。但是，对视力强的腹侧滑坡（206°s-1）的反应会根据视差的存在或不存在而发生剧烈变化。