cobweb spiders vs Common harp ground beetle

Steatoda grossa compared with Amara communis

Taxonomic Classification

Rank	cobweb spiders	Common harp ground beetle
Kingdom same	Animalia (Animals)	Animalia (Animals)
Phylum same	Arthropoda (Arthropods)	Arthropoda (Arthropods)
Class	Arachnida (Arachnids)	Insecta (Insects)
Order	Araneae (Araneae)	Coleoptera (Beetles)
Family	Theridiidae	Carabidae
Genus	Steatoda	Amara
Species	Steatoda grossa	Amara communis

Evolutionary Relationship

cobweb spiders and Common harp ground beetle share a common ancestor at the Phylum level: Arthropoda. (Arthropods)

Conservation Status

cobweb spiders

LC — Least Concern

Common harp ground beetle

LC — Least Concern

Physical Characteristics

Attribute	cobweb spiders	Common harp ground beetle
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 harp ground beetle

Habitat

Typically found in virtually all terrestrial and freshwater habitats.

Range

Found across Europe (5 countries) and North America (Canada, United States).

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 harp ground beetle

The common harp ground beetle, <em>Amara communis</em>, is an insect belonging to the order Coleoptera, family Carabidae, the ground beetles. This species is distributed across Europe and North America, indicating a wide Holarctic range. Ground beetles of the genus Amara are typically found in a variety of terrestrial habitats including grasslands, agricultural fields, woodland margins, and disturbed areas. Members of this genus are generally omnivorous or seed-feeding, and some are known to consume weed seeds, giving them potential ecological significance in agroecosystems. <em>Amara communis</em> is assessed as Least Concern on the IUCN Red List, reflecting stable populations across its range. No dietary information has been provided specifically for this species in current records. Biological traits of this species remain poorly documented in the scientific literature.

Shared Countries

Both species can be found in 5 countries:

🇧🇪 Belgium 🇨🇦 Canada 🇩🇰 Denmark 🇸🇪 Sweden 🇺🇸 United States