The role of a non-native host plant in altering the seasonal dynamics of Danaus plexippus (Lepidoptera: Nymphalidae) development.

Insect herbivores often experience seasonal fluctuation in food availability, which plays important role in signaling diapause and/or migration. However, the introduction of non-native plants with different seasonal phenologies has the potential to disrupt these dynamics. Some evidence suggests that this may be a developing issue for the annual migration of the monarch butterfly Danaus plexippus (Linnaeus) (Lepidoptera: Nymphalidae). The tropical milkweed Asclepias curassavica (Linnaeus) (Gentianales: Apocynaceae), which does not seasonally senesce to the same extent or rate as native milkweed host plants, has recently been introduced into the North American mainland population. Here, we report an experimental comparison of monarch developmental success when reared on A. curassavica and the native A. incarnata (Linnaeus) (Gentianales: Apocynaceae) in the summer and fall. We found that A. curassavica facilitates monarch development later into their typical migratory and over-wintering season, despite several prolonged periods where the temperature was below requirements for growth and development.