cobweb spiders vs Common Kidney-Vetch

Steatoda grossa compared with Anthyllis vulneraria

Key Differences

cobweb spiders is Least Concern while Common Kidney-Vetch is Vulnerable.

Taxonomic Classification

Rank	cobweb spiders	Common Kidney-Vetch
Kingdom	Animalia (Animals)	Plantae (Plants)
Phylum	Arthropoda (Arthropods)	Magnoliophyta (Flowering Plants)
Class	Arachnida (Arachnids)	Magnoliopsida (Dicots)
Order	Araneae (Araneae)	Fabales (Legumes & Allies)
Family	Theridiidae	Fabaceae
Genus	Steatoda	Anthyllis
Species	Steatoda grossa	Anthyllis vulneraria

Conservation Status

cobweb spiders

LC — Least Concern

Common Kidney-Vetch

VU — Vulnerable

Physical Characteristics

Attribute	cobweb spiders	Common Kidney-Vetch
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 Kidney-Vetch

Habitat

Found across multiple habitat types including tropical and subtropical moist broadleaf forests, temperate broadleaf and mixed forests, and temperate coniferous forests, among 6 distinct biome types spanning the Indomalayan and Oceanian and Palearctic realms. Populations are also found in montane and highland environments at higher elevations.

Range

Widely distributed across Africa (Libya), Asia (Japan), Europe (9 countries), North America (Canada, United States), and Oceania and the Pacific (Australia). Currently classified as Vulnerable on the IUCN Red List, this species faces significant conservation challenges across its range.

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 Kidney-Vetch

Common Kidney-Vetch (<em>Anthyllis vulneraria</em>) is a flowering plant in the legume family Fabaceae, assessed as Vulnerable on the IUCN Red List due to habitat degradation and agricultural intensification across parts of its range. It is widely distributed across Africa (Libya), Asia (Japan), Europe (nine countries), North America (Canada and the United States), and Oceania (Australia), occupying six distinct biome types and occurring within the Indomalayan and Oceanian biogeographic realms. The species typically grows in dry, calcareous grasslands, coastal cliffs, sand dunes, and rocky slopes, often favoring nutrient-poor soils. It is an important larval food plant for certain butterfly species, particularly the Small Blue butterfly in Europe, and contributes to soil fertility through nitrogen fixation via root nodules. Its cheerful yellow, orange, or red flower heads make it a recognizable component of chalk and limestone grassland communities. Biological traits of this species remain poorly documented in the scientific literature.