Broom Flat-body vs cobweb spiders

Agonopterix scopariella compared with Steatoda grossa

Key Differences

• Broom Flat-body is Near Threatened while cobweb spiders is Least Concern.

Taxonomic Classification

Rank	Broom Flat-body	cobweb spiders
Kingdom same	Animalia (Animals)	Animalia (Animals)
Phylum same	Arthropoda (Arthropods)	Arthropoda (Arthropods)
Class	Insecta (Insects)	Arachnida (Arachnids)
Order	Lepidoptera (Butterflies & Moths)	Araneae (Araneae)
Family	Depressariidae	Theridiidae
Genus	Agonopterix	Steatoda
Species	Agonopterix scopariella	Steatoda grossa

Evolutionary Relationship

Broom Flat-body and cobweb spiders share a common ancestor at the Phylum level: Arthropoda. (Arthropods)

Conservation Status

Broom Flat-body

NT — Near Threatened

cobweb spiders

LC — Least Concern

Physical Characteristics

Attribute	Broom Flat-body	cobweb spiders
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Broom Flat-body

Habitat

Typically found in virtually all terrestrial and freshwater habitats.

Range

Distributed across Belgium, Denmark, Norway, Portugal, and Sweden. Listed as Near Threatened, this species requires ongoing monitoring to prevent population decline.

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).

Broom Flat-body

The Broom Flat-Body (Agonopterix scopariella) is a species in the genus Agonopterix. It is currently classified as Near Threatened on the IUCN Red List. Typically found in virtually all terrestrial and freshwater habitats.

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.

Shared Countries

Both species can be found in 4 countries:

🇧🇪 Belgium 🇩🇰 Denmark 🇵🇹 Portugal 🇸🇪 Sweden