Tibiotarsal-chaetotaxy
Guides
Willemia
Willemia is a genus of springtails (Collembola) in the family Hypogastruridae comprising at least 40 described species. Species occupy diverse habitats including sandy substrates (psammophily) and loam soils, with some inhabiting harsh environments such as polar regions, high mountains, and deserts. Phylogenetic studies indicate that psammophily is ancestral in this genus and has been lost twice independently, demonstrating that habitat specialization can be evolutionarily reversible. Species utilizing harsh environments tend to have low clade ranks and are concentrated on former Laurasian continents.