Quasisocial
Guides
Anelosimus
cobweb spiders
Anelosimus is a genus of cobweb spiders (Theridiidae) renowned as a model system for studying the evolution of sociality in arachnids. The genus contains approximately 75 species exhibiting the full spectrum of social organization, from solitary to highly social (quasisocial). Eight quasisocial species have been documented, more than any other spider genus. Social species such as Anelosimus eximius form massive communal webs housing tens of thousands of individuals, while solitary species occur at higher altitudes and latitudes. The genus is cosmopolitan, with significant diversity in the Americas, Madagascar, and Australasia.
Xylosandrus germanus
black stem borer, alnus ambrosia beetle, black timber bark beetle
Xylosandrus germanus is a tiny ambrosia beetle native to eastern Asia that has become a significant invasive pest in Europe and North America. Females, which are flight-capable and substantially larger than the flightless males, excavate galleries in stressed or recently dead woody plants to cultivate fungal gardens. The species exhibits a quasisocial structure with foundress females performing distinct behavioral roles that shift from gallery construction and brood care to entrance-blocking as the colony matures. Its rapid spread—tens of kilometers per year in some regions—is facilitated by climate change, global timber trade, and an unusual reproductive system where single foundresses can establish populations through sib-mating.