Performance of early instar monarch butterflies (Danaus plexippus L.) on nine milkweed species native to Iowa

Authors: POCIUS, VICTORIA - Iowa State University; DEBINSKI, DIANE - Iowa State University; Bidne, Keith; Hellmich Ii, Richard; HUNTER, FRANCES - Iowa State University

Submitted to: Journal of Lepidopterists Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/3/2017
Publication Date: 9/7/2017
Citation: Pocius, V.M., Debinski, D.M., Bidne, K.G., Hellmich II, R.L., Hunter, F.K. 2017. Performance of early instar monarch butterflies (Danaus plexippus L.) on nine milkweed species native to Iowa. Journal of Lepidopterists Society. 71(3):153-161. https://doi.org/10.18473/lepi.71i3.a5.
DOI: https://doi.org/10.18473/lepi.71i3.a5

Interpretive Summary: The population of monarch butterflies east of the Rocky Mountains has experienced a significant decline over the past two decades due to many factors including loss of habitat. Thus, habitat restoration within the summer breeding range is crucial to boost population numbers. Monarch butterfly caterpillars (or larvae) use milkweeds as their only host plant. However, larval preferences among milkweed species are not well documented. We examined larval survival and feeding on nine milkweed species native to Iowa, because this region is a conservation priority area within the summer breeding range. Our goal was to compare how monarch larvae would survive and grow on nine different milkweed species with overlapping ranges. Species examined included Asclepias exaltata (Poke Milkweed), A. hirtella (Tall Green Milkweed), A. incarnata (Swamp Milkweed), A. speciosa (Showy Milkweed), A. sullivantii (Prairie Milkweed), A. syriaca (Common Milkweed), A. tuberosa (Butterfly Milkweed), A. verticillata (Whorled Milkweed), and C. laeve (Honeyvine Milkweed). In laboratory and greenhouse experiments, larval survival on all nine milkweed species did not differ. Larvae that fed on C. laeve plants were an instar behind larvae that fed on any other species, while larvae that fed on A. verticillata weighed more than larvae that fed on any other species. Our results show that all nine milkweed species are suitable hosts for monarch larvae. Thus, restoration efforts including a diversity of milkweed species could benefit monarchs in their summer range. This information is useful to all groups interested in restoring habitat for monarch butterflies.

Technical Abstract: Over the past two decades, the population of monarch butterflies east of the Rocky Mountains has experienced a significant decline. Habitat restoration within the summer breeding range is crucial to boost population numbers. Monarch butterfly larvae use milkweeds as their only host plant. However, larval preferences among milkweed species are not well documented. We examined larval survival and feeding on nine milkweed species native to Iowa, because this region is a conservation priority area within the summer breeding range. Our goal was to compare how monarch larvae would survive and grow on nine different milkweed species with overlapping ranges. Species examined included Asclepias exaltata (Poke Milkweed), A. hirtella (Tall Green Milkweed), A. incarnata (Swamp Milkweed), A. speciosa (Showy Milkweed), A. sullivantii (Prairie Milkweed), A. syriaca (Common Milkweed), A. tuberosa (Butterfly Milkweed), A. verticillata (Whorled Milkweed), and C. laeve (Honeyvine Milkweed). In laboratory and greenhouse experiments, larval survival on all nine milkweed species did not differ. Larvae that fed on C. laeve plants were an instar behind larvae that fed on any other species, while larvae that fed on A. verticillata weighed more than larvae that fed on any other species. Our results show that all nine milkweed species are suitable hosts for monarch larvae. Thus, restoration efforts including a diversity of milkweed species could benefit monarchs in their summer range.