The hemlock looper, Lambdina fiscellaria, is a major defoliator of coniferous forests. As looper larvae are known for their wandering habits, we determined the underlying behavioral mechanisms that enable them to orient in the environment. First, we quantified the response of all larval stages to light or gravity, and to both stimuli tested simultaneously. Second, we evaluated the combined effect of substrate texture and light on the selection of pupation sites by wandering mature larvae (4th instar +10 days). We found that light attracted neonates and newly molted larvae of all stages, but response indices decreased significantly between the second and third larval stages. In a 45° inclined tube, larvae showed a geonegative response that remained relatively constant from one stage to the next. No synergy between the two stimuli was observed when a light source was placed on top of the inclined tube. In contrast, when the light source was placed at the base, the light signal dominated the gravity stimulus. Finally, wandering larvae were indifferent to unidirectional light and reacted positively to gravity. They preferred to pupate in a dark environment, a choice that could be modulated by positive photokinesis. Their final selection of a pupation site also involved physical contact with the substrate, which resembles positive thigmokinesis. The ecological significance of these results is discussed in relation to the spatial distribution of the various larval stages on host trees.

毒铁loop，Lambdina fiscellaria，是针叶林的主要落叶树。由于loop鱼幼虫以其流浪习惯而闻名，我们确定了使它们能够在环境中定向的潜在行为机制。首先，我们量化了所有幼虫阶段对光或重力的响应，以及对同时测试的两种刺激的响应。其次，我们通过游荡成熟的幼虫（四龄+10天）评估了基质质地和光照对化脓位点选择的综合作用。我们发现光吸引了所有阶段的新生儿和新蜕变的幼虫，但是响应指数在第二和第三幼虫阶段之间显着下降。在45°倾斜的试管中，幼虫显示出负向性反应，从一个阶段到下一个阶段都保持相对恒定。当将光源放置在倾斜管的顶部时，未观察到两个刺激之间的协同作用。相反，当将光源放置在基座上时，光信号在重力刺激中占主导地位。最后，徘徊的幼虫对单向光无动于衷，并对重力产生积极的反应。他们更喜欢在黑暗的环境中化脓，而这种选择可以通过正向光动力学调节。他们最后对化脓位点的选择还涉及与底物的物理接触，这类似于阳性的硫代木激酶。讨论了这些结果的生态意义，涉及寄主树上各个幼虫阶段的空间分布。徘徊的幼虫对单向光无动于衷，并且对重力有积极的反应。他们更喜欢在黑暗的环境中化脓，而这种选择可以通过正向光动力学调节。他们最后对化脓位点的选择还涉及与底物的物理接触，这类似于阳性的硫代木激酶。讨论了这些结果的生态意义，涉及寄主树上各个幼虫阶段的空间分布。徘徊的幼虫对单向光无动于衷，并且对重力有积极的反应。他们更喜欢在黑暗的环境中化脓，而这种选择可以通过正向光动力学调节。他们最后对化脓位点的选择还涉及与底物的物理接触，这类似于阳性的硫代木激酶。讨论了这些结果的生态意义，涉及寄主树上各个幼虫阶段的空间分布。