cobweb spiders vs common greasewort

Steatoda grossa compared with Aneura pinguis

Taxonomic Classification

Rank	cobweb spiders	common greasewort
Kingdom	Animalia (Animals)	Plantae (Plants)
Phylum	Arthropoda (Arthropods)	Marchantiophyta (liverwort)
Class	Arachnida (Arachnids)	Jungermanniopsida (Jungermanniopsida)
Order	Araneae (Araneae)	Metzgeriales (Metzgeriales)
Family	Theridiidae	Aneuraceae
Genus	Steatoda	Aneura
Species	Steatoda grossa	Aneura pinguis

Conservation Status

cobweb spiders

LC — Least Concern

common greasewort

LC — Least Concern

Physical Characteristics

Attribute	cobweb spiders	common greasewort
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

cobweb spiders

Habitat

Typically found in terrestrial habitats from forests to deserts.

Range

Widely distributed across Africa (South Africa), Europe (29 countries), North America (Canada, United States), and South America (Ecuador).

common greasewort

Habitat

Native to Asia and Europe and North America, inhabiting ecosystems characteristic of the region.

Range

Widely distributed across Asia (Taiwan), Europe (6 countries), North America (United States), and South America (Brazil, Colombia).

cobweb spiders

The false black widow (Steatoda grossa) is a cosmopolitan cobweb spider in the family Theridiidae, often mistaken for the true black widow due to its similarly dark, globose abdomen, though it lacks the red hourglass marking. Females reach 6–10 millimeters in body length and display a deep purplish-brown to nearly black coloration with faint pale markings on the dorsal abdomen. Originally native to western Europe, Steatoda grossa has spread globally through human commerce, establishing populations in Australia, New Zealand, North America, and other regions where it thrives in human structures including homes, sheds, and outbuildings. The spider constructs a persistent, tangled cobweb in sheltered corners and recesses, where it captures woodlice, ants, beetles, and other arthropods—notably targeting invertebrates that many other spiders avoid. The venom of S. grossa causes steatodism, a syndrome of localized pain, sweating, and systemic discomfort that is rarely serious but can cause significant distress. Interestingly, the antivenin produced for Latrodectus (true widow) spider bites has been shown to effectively treat Steatoda envenomations, underscoring the phylogenetic relatedness of these genera. Females produce several egg sacs during a season, each containing dozens of eggs wrapped in distinctive silken cocoons. The species is classified as Least Concern given its expanding global distribution facilitated by human activity.

common greasewort

<em>Aneura pinguis</em>, commonly known as common greasewort, is a liverwort belonging to the genus Aneura within the family Aneuraceae. This cryptogamic plant inhabits ecosystems across Asia, Europe, and North America, thriving in moist or waterlogged environments. Its range encompasses Taiwan in Asia, six European countries, the United States in North America, and Brazil and Colombia in South America, indicating a broad geographic distribution across multiple continents. Common greasewort is assessed as Least Concern on the IUCN Red List. The species typically forms flat, ribbon-like thalli in damp habitats such as stream banks, wet rocks, and boggy ground. Biological traits of this species remain poorly documented in the scientific literature.