cobweb spiders vs Common Sun Beetle

Steatoda grossa compared with Amara aenea

Taxonomic Classification

Rank	cobweb spiders	Common Sun 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 aenea

Evolutionary Relationship

cobweb spiders and Common Sun Beetle share a common ancestor at the Phylum level: Arthropoda. (Arthropods)

Conservation Status

cobweb spiders

LC — Least Concern

Common Sun Beetle

LC — Least Concern

Physical Characteristics

Attribute	cobweb spiders	Common Sun 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 Sun Beetle

Habitat

Typically found in virtually all terrestrial and freshwater habitats.

Range

Found across Europe (7 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 Sun Beetle

<em>Amara aenea</em>, the common sun beetle, is a carabid ground beetle in the family Carabidae, order Coleoptera. It is broadly distributed across Europe and has been introduced to North America, typically inhabiting open, sunny habitats such as arable fields, grasslands, sandy heathlands, and disturbed ground with sparse vegetation. Adults are omnivorous, feeding on seeds, small invertebrates, and plant material, and are considered important predators of weed seeds in agricultural systems. <em>Amara aenea</em> is surface-active during warm, dry conditions, typically exhibiting peak activity in late spring and summer. Like many carabid beetles, it is nocturnal and shelters under stones and debris during the day. Larvae develop in the soil, where they also feed on organic matter and small invertebrates. Biological traits including precise adult lifespan, body length measurements, and detailed prey preferences remain poorly documented at the species level. The species is assessed as Least Concern by the IUCN, reflecting its wide distribution, high adaptability to disturbed environments, and no significant known threats to global population status.

Shared Countries

Both species can be found in 7 countries:

🇧🇪 Belgium 🇨🇦 Canada 🇩🇰 Denmark 🇵🇹 Portugal 🇪🇸 Spain 🇸🇪 Sweden 🇺🇸 United States