West Coast Lady Butterfly
Vanessa annabella
NatureServe conservation status
Global (G-rank): G5
State (S-rank): S3
Utah Wildlife Action Plan status
- SGCN
External links
General information
The West coast lady, Vanessa annabella, is a widespread western species that can be found in a variety of natural and anthropogenic habitats. This once ubiquitous butterfly is undergoing population declines that rival the monarch; long term data suggest this species is declining rapidly and consistently across much of its range and may soon be rare in many locations, with many extirpated populations.
Habitat
Open, often disturbed areas, wherever its larval hosts, the family Malvaceae and the genus Urtica, occur.
Food habits
Vanessa annabella is a moderate host specialist, with its caterpillars able to feed on plants only within the families Malvaceae and Urticaceae. These plants are found across a variety of habitats but typically require a shallow water table or nearby water source and occasional disturbances. Several of these plant species grow in areas where humans typically remove vegetation since they compete with agricultural crops or have other undesirable traits such as physical irritation and waterway blockages (e.g., as caused by Urtica dioica and U. urens) (Schellman and Shrestha 2008).
Vanessa annabella populations are known to use multiple nonnative species related to native plants as food plants for caterpillars. For V. annabella, nonnative plants include Malva neglecta, M. nicaeensis, M. parviflora, M. pusilla, M. sylvestris, and Urtica urens (Scott 1986).
Threats or limiting factors
Warming autumnal temperatures and habitat loss and degradation due to the use of pesticides are some of the driving forces behind this decline. V. annabella has been found to be consistently declining at multiple long term monitoring sites across its range.
Though it is native, the host plant U. dioica is considered invasive by the Invasive Plant Atlas of the United States and the U.S. Forest Service (United States and University of Georgia 2010; USFS 2022), and may be targeted for selective mechanical or chemical removal.
Malva neglecta in particular may be targeted as an undesirable plant in Utah and across the western United States (Lowry et al. 2014). While some of these nonnative host plant species have a broad geographic range, their undesirable status and preference for disturbed habitats make them prime targets for removal using mechanical means or herbicides in urban environments, transportation right-of-ways, and agricultural settings. These herbicide applications may directly remove potential caterpillar host plants and cause mortality in caterpillars if plants are killed mid-development.