Over the past two decades, the population of monarch butterflies east of the Rocky Mountains has experienced a significant decline in overwintering numbers. Habitat restoration that includes planting milkweeds is essential to boost monarch numbers within the breeding range. Milkweeds are the only host plants for larval monarch butterflies, but female oviposition preference for different milkweed species, especially those with overlapping ranges, is not well documented. We examined the relative inclination to lay eggs on nine milkweed species native to Iowa (no choice), and oviposition preference (choice) among the four most commonly occurring Iowa species (Asclepias incarnata, Asclepias syriaca, Asclepias tuberosa, and Asclepias verticillata). In both experiments, eggs were counted daily for four days. The milkweeds tested were Asclepias exaltata (poke milkweed), Asclepias hirtella (tall green milkweed), A. incarnata (swamp milkweed), Asclepias speciosa (showy milkweed), Asclepias sullivantii (prairie milkweed), A. syriaca (common milkweed), A. tuberosa (butterfly milkweed), A. verticillata (whorled milkweed), and Cynanchum laeve (honeyvine milkweed). When females were given only a single species on which to lay eggs, there were significant differences among milkweed species in the average number of eggs laid; A. incarnata had the highest average egg count. When females were given a choice among A. incarnata, A. syriaca, A. tuberosa, and A. verticillata, there were also differences among milkweed species in the number of eggs laid; again, A. incarnata had the highest average number of eggs laid. Additionally, females laid more total eggs when four plants of different milkweed species were available than when there were four plants of a single milkweed species. Our results show that monarch butterflies will lay eggs on all nine milkweeds, but that there are clear preferences for some milkweed species over others.

The Iowa Monarch Conservation Consortium was established March 2015. Adding milkweeds to agricultural landscapes is one of many Consortium goals. In order to further monarch butterfly conservation efforts, scientists need more information about milkweed phenology and persistence on the landscape, and how monarchs are using these plants, because milkweeds now are absent from most agricultural fields. This is the second year of a study to examine both oviposition preference and larval survival on nine milkweed species endemic to Iowa. These data will be used as a baseline for informing monarch habitat conservation and restoration efforts across the Midwest.

The Iowa Monarch Conservation Consortium was established March 2015. Adding milkweeds to agricultural landscapes is one of many Consortium goals. In order to further monarch butterfly conservation efforts, scientists need more information about milkweed phenology and persistence on the landscape, and how monarchs are using these plants, because milkweeds now are absent from most agricultural fields. This is the second year of a study to examine both oviposition preference and larval survival on nine milkweed species endemic to Iowa. These data will be used as a baseline for informing monarch habitat conservation and restoration efforts across the Midwest.

The Iowa Monarch Conservation Consortium was established March 2015. Adding milkweeds to agricultural landscapes is one of many Consortium goals. In order to further monarch butterfly conservation efforts, scientists need more information about milkweed phenology and persistence on the landscape, and how monarchs are using these plants, because milkweeds now are absent from most agricultural fields. This is the second year of a study to examine both oviposition preference and larval survival on nine milkweed species endemic to Iowa. These data will be used as a baseline for informing monarch habitat conservation and restoration efforts across the Midwest.

The population of monarch butterflies east of the Rocky Mountains has experienced a significant decline over the past 20 yr. In order to increase monarch numbers in the breeding range, habitat restoration that includes planting milkweed plants is essential. Milkweeds in the genus Asclepias and Cynanchum are the only host plants for larval monarch butterflies in North America, but larval performance and survival across nine milkweeds native to the Midwest is not well documented. We examined development and survival of monarchs from first-instar larval stages to adulthood on nine milkweed species native to Iowa. The milkweeds included Asclepias exaltata (poke milkweed) (Gentianales: Apocynaceae), Asclepias hirtella (tall green milkweed) (Gentianales: Apocynaceae), Asclepias incarnata (swamp milkweed) (Gentianales: Apocynaceae), Asclepias speciosa (showy milkweed) (Gentianales: Apocynaceae), Asclepias sullivantii (prairie milkweed) (Gentianales: Apocynaceae), Asclepias syriaca (common milkweed) (Gentianales: Apocynaceae), Asclepias tuberosa (butterfly milkweed) (Gentianales: Apocynaceae), Asclepias verticillata (whorled milkweed) (Gentianales: Apocynaceae), and Cynanchum laeve (honey vine milkweed) (Gentianales: Apocynaceae). In greenhouse experiments, fewer larvae that fed on Asclepias hirtella and Asclepias sullivantii reached adulthood compared with larvae that fed on the other milkweed species. Monarch pupal width and adult dry mass differed among milkweeds, but larval duration (days), pupal duration (days), pupal mass, pupal length, and adult wet mass were not significantly different. Both the absolute and relative adult lipids were different among milkweed treatments; these differences are not fully explained by differences in adult dry mass. Monarch butterflies can survive on all nine milkweed species, but the expected survival probability varied from 30 to 75% among the nine milkweed species.

The Iowa Monarch Conservation Consortium was established March 2015. Adding milkweeds to agricultural landscapes is one of many Consortium goals. In order to further monarch butterfly conservation efforts, scientists need more information about milkweed phenology and persistence on the landscape, and how monarchs are using these plants, because milkweeds now are absent from most agricultural fields. This is the second year of a study to examine both oviposition preference and larval survival on nine milkweed species endemic to Iowa. These data will be used as a baseline for informing monarch habitat conservation and restoration efforts across the Midwest.

The Iowa Monarch Conservation Consortium was established March 2015. Adding milkweeds to agricultural landscapes is one of many Consortium goals. In order to further monarch butterfly conservation efforts, scientists need more information about milkweed phenology and persistence on the landscape, and how monarchs are using these plants, because milkweeds now are absent from most agricultural fields. This is the second year of a study to examine both oviposition preference and larval survival on nine milkweed species endemic to Iowa. These data will be used as a baseline for informing monarch habitat conservation and restoration efforts across the Midwest.

Over the past two decades, the population of monarch butterflies east of the Rocky Mountains has experienced a significant decline. Habitat restoration that includes milkweed plants is crucial to boost population numbers in the breeding range. Monarch butterfly larvae use milkweeds as their only host plant, but larval performance on different milkweed species is not well documented. We examined early instar survival and growth on nine milkweed species native to Iowa. These 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 Cynanchum laeve (honey vine 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 early instar larvae can survive on all nine milkweed species.

The Iowa Monarch Conservation Consortium was established March 2015. Adding milkweeds to agricultural landscapes is one of many Consortium goals. In order to further monarch butterfly conservation efforts, scientists need more information about milkweed phenology and persistence on the landscape, and how monarchs are using these plants, because milkweeds now are absent from most agricultural fields. This is the second year of a study to examine both oviposition preference and larval survival on nine milkweed species endemic to Iowa. These data will be used as a baseline for informing monarch habitat conservation and restoration efforts across the Midwest.

The Iowa Monarch Conservation Consortium was established March 2015. Adding milkweeds to agricultural landscapes is one of many Consortium goals. In order to further monarch butterfly conservation efforts, scientists need more information about milkweed phenology and persistence on the landscape, and how monarchs are using these plants, because milkweeds now are absent from most agricultural fields. This is the second year of a study to examine both oviposition preference and larval survival on nine milkweed species endemic to Iowa. These data will be used as a baseline for informing monarch habitat conservation and restoration efforts across the Midwest.