Invasive paper wasp turns urban pollinator gardens into ecological traps for monarch butterfly larvae
Baker AM, Potter DA. Scientific reports, June 2020.
Read the paper Free to read · doi:10.1038/s41598-020-66621-6
What this paper is about
Urban gardeners are encouraged to plant milkweed, and the European paper wasp is abundant in cities. The wasp preys heavily on monarch caterpillars.
The result is an ecological trap: females lay on garden milkweed, and the caterpillars are eaten at a rate that makes the planting worse than useless at those sites.
Summarised here from the abstract below. Not the authors’ words.
Abstract
Invasive species can be particularly disruptive when they intersect with organisms of conservation concern. Stabilizing the declining eastern migratory population of monarch butterflies (Danaus plexippus) is projected to require extensive habitat restoration across multiple land use sectors including metropolitan areas. Numerous conservation programs encourage urban citizens to plant gardens with milkweeds, the obligate larval host plants of the monarch. Here, we show that predation by Polistes dominula, an invasive paper wasp that is particularly abundant in urban settings, can turn such sites into ecological traps for monarch larvae. Polistes dominula was the predominant paper wasp seen foraging in central Kentucky pollinator gardens. In 120 observed encounters with monarch larvae on milkweeds in gardens, most second to fourth instars were killed, whereas most fifth instars escaped by thrashing or dropping. The wasps bit and carried off second instars whole, whereas third and fourth instar kills were first gutted, then processed and carried away piecemeal. Predation on sentinel larvae was much higher in urban gardens than in rural settings. The wasps exploited ornamental butterfly "hibernation boxes" in pollinator gardens as nesting habitat. Polistes dominula is an under-recognized predator that may diminish the urban sector's contributions to monarch habitat restoration.
Abstract reproduced from the published paper, which is licensed CC BY. Copyright remains with the authors.
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Milkweed USA. (2026). Invasive paper wasp turns urban pollinator gardens into ecological traps for monarch butterfly larvae (listing). Retrieved DATE, from https://milkweedusa.com/research/invasive-paper-wasp-turns-urban-pollinator-gardens-into-ecological-2020/
"Invasive paper wasp turns urban pollinator gardens into ecological traps for monarch butterfly larvae (listing)." Milkweed USA, 2026, https://milkweedusa.com/research/invasive-paper-wasp-turns-urban-pollinator-gardens-into-ecological-2020/. Accessed DATE.
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@misc{milkweedusa_researchinvasivepaperwasptur,
title = {Invasive paper wasp turns urban pollinator gardens into ecological traps for monarch butterfly larvae (listing)},
author = {{Milkweed USA}},
year = {2026},
url = {https://milkweedusa.com/research/invasive-paper-wasp-turns-urban-pollinator-gardens-into-ecological-2020/},
note = {Accessed DATE}
}