Growing native plants in urban gardens is often promoted as a possible means of increasing lepidopteran populations. However, the efficacy of such efforts has not been well studied. Lepidopterans vary widely in their ability to survive in cities, and the few previous studies of caterpillar abundance or biomass across an urban-rural gradient have yielded mixed results. We placed clay caterpillar models in native plant gardens to assess whether the attack rate on these models varied with degree of urbanization (percent impervious surface within 1 km radius of each garden), and whether responses differed across predator taxa. We also examined how garden characteristics (plant biovolume density, plant species richness) affected probability of attack. Overall, attack rates on these models decreased with increasing impervious surface, although predator taxa varied in their sometimes complex responses. For parasitoid wasps, which accounted for 47% of all attacks, increasing biovolume density increased attack probability at impervious surface levels below 35%, but decreased the probability of attack at higher levels of impervious surface. In contrast, probabilities of attack by both predatory wasps and vertebrates decreased with increasing percent impervious surface, but did not vary with impervious surface for ants and spiders. Predation on caterpillars in urban gardens may be lower than in rural ones; however, this potential increase in survival may be a result of declines in some predator taxa, such as predatory wasps and insectivorous birds. More studies across an urban gradient are needed to measure factors other than predation that influence caterpillar survival in gardens.

通常建议在城市花园中种植本地植物，作为增加鳞翅目种群的可能手段。但是，这种努力的功效尚未得到很好的研究。鳞翅目动物在城市中生存的能力差异很大，而先前关于城乡梯度上的毛毛虫丰度或生物量的研究很少。我们将粘土毛毛虫模型放置在原生植物花园中，以评估这些模型的攻击率是否随城市化程度（每个花园1 km半径内的不透水百分比）的变化而变化，以及不同食肉类群的反应是否不同。我们还检查了花园特征（植物生物量密度，植物物种丰富度）如何影响侵袭概率。总体而言，这些模型的攻击率会随着不透水面的增加而降低，尽管捕食者的类群有时反应复杂，但差异很大。对于寄生虫类黄蜂（占所有攻击的47％），增加生物体积密度可增加在35％以下的不透水表面水平时的攻击机率，但会降低在不透水表面较高水平时的攻击机率。相反，掠食性黄蜂和脊椎动物的攻击概率随着不透水表面百分比的增加而降低，但对于蚂蚁和蜘蛛而言，不透水表面没有变化。城市花园中的毛毛虫捕食率可能低于农村地区的毛虫；但是，这种潜在的生存增加可能是某些捕食类群（例如掠食性黄蜂和食虫鸟）数量下降的结果。除掠食性因素外，还需要进行更多关于城市梯度的研究，这些因素会影响花园中毛虫的生存。