Laboratory refugia preferences of the brown widow spider,Latrodectus geometricus(Araneae: Theridiidae)

Urban Environments Aid Invasion of Brown Widows (Theridiidae: Latrodectus geometricus) in North America, Constraining Regions of Overlap and Mitigating Potential Impact on Native Widows

“…An experimental study found that L. geometricus prefer websites with deep cavities and 30 • or 90 • angles, a prominent feature of urban architecture, because these angles fit the conical retreats of L. geometricus web structures (Vetter et al, 2016). Unlike black widows, they also prefer web-sites that have been previously occupied by conspecifics (Vetter et al, 2016).…”

“…An experimental study found that L. geometricus prefer websites with deep cavities and 30 • or 90 • angles, a prominent feature of urban architecture, because these angles fit the conical retreats of L. geometricus web structures (Vetter et al, 2016). Unlike black widows, they also prefer web-sites that have been previously occupied by conspecifics (Vetter et al, 2016). In the field, brown widows are often found under objects with minimal but strong material cover that contain 30 • /90 angles, such as between fencing, in gaps of objects like trash bin handles, and under tables and chairs with solid tops (Vetter et al, 2012).…”

“…North America is also home to four native widow species: western (L. hesperus), southern (L. mactans), northern (L. variolus), and red (L. bishopi) widows. Black and brown widows are large-range, generalist predators, and generally prefer low, dark corners of low-traffic areas of residences to build their distinctive tangle-web shelters (Vetter et al, 2016). Latrodectus geometricus almost exclusively reside in the presence of humans, including in their native range, whereas black widows opportunistically use urban structures for shelter while maintaining populations in their native habitats (Lamoral, 1968;Johnson et al, 2012;Schraft et al, 2021).…”

“…Latrodectus geometricus almost exclusively reside in the presence of humans, including in their native range, whereas black widows opportunistically use urban structures for shelter while maintaining populations in their native habitats (Lamoral, 1968;Johnson et al, 2012;Schraft et al, 2021). Previous experimental studies have demonstrated that L. geometricus show significant preference for establishing tangle-web refugia on rough surfaces and tight spaces with acute, 30 • angles that are more frequently observed in urban architecture than in nature (Gutiérrez-Fonseca and Ortiz-Rivas, 2014;Vetter et al, 2016). Unlike their relatives, red widows (L. bishopi) do not live with humans at all, and are endemic to sand pine scrub habitats in Florida where they build retreats almost exclusively on saw palmetto (Serenoa repens) (Carrel, 2001;Carrel and Deyrup, 2014).…”

Climatic niche overlap models reveal niche partitioning among black widow spiders and potential ecological impacts of invasive brown widows in North America

“…Given the chance of negative encounters, there is possible risk of ecological impact in the long-term, depending on synergistic factors like colonization/ propagule pressure, biotic resistance, or enemy release (Ricciardi et al 2013). However, L. geometricus' preference for urban habitats may limit potential impact on non-urban widow populations: differences in diet or microhabitats, such as an apparent preference for human-made structures as web-building sites (Vetter et al 2016), might allow L. geometricus to co-occur with L. hesperus and L. mactans despite climatic niche overlap. Our previous work has also shown that L. geometricus prefers urban environments over non-urban environments, in contrast to their native congeners (Sadir and Marske 2021).…”