Brook Floater vs Cobweb Spiders

Alasmidonta varicosa compared with Parasteatoda tepidariorum

Key Differences

• Brook Floater is Vulnerable while Cobweb Spiders is Least Concern.

Taxonomic Classification

Rank	Brook Floater	Cobweb Spiders
Kingdom same	Animalia (Animals)	Animalia (Animals)
Phylum	Mollusca (Mollusks)	Arthropoda (Arthropods)
Class	Bivalvia (Bivalvia)	Arachnida (Arachnids)
Order	Unionida (Unionida)	Araneae (Araneae)
Family	Unionidae	Theridiidae
Genus	Alasmidonta	Parasteatoda
Species	Alasmidonta varicosa	Parasteatoda tepidariorum

Evolutionary Relationship

Brook Floater and Cobweb Spiders share a common ancestor at the Kingdom level: Animalia. (Animals)

Conservation Status

Brook Floater

VU — Vulnerable

Cobweb Spiders

LC — Least Concern

Physical Characteristics

Attribute	Brook Floater	Cobweb Spiders
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Brook Floater

Habitat

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

Range

Found in United States. Currently classified as Vulnerable on the IUCN Red List, this species faces significant conservation challenges across its range.

Cobweb Spiders

Habitat

Typically found in terrestrial habitats from forests to deserts.

Range

Widely distributed across Africa (South Africa), Asia (Taiwan), Europe (7 countries), North America (Canada, United States), and South America (Colombia).

Brook Floater

The Brook Floater (Alasmidonta varicosa) is a species in the genus Alasmidonta. It is currently classified as Vulnerable on the IUCN Red List. Native to North America, inhabiting ecosystems characteristic of the region.

Cobweb Spiders

The common house spider (Parasteatoda tepidariorum) is one of the most cosmopolitan of all spider species, having followed human civilization to virtually every inhabited corner of the globe. A member of the family Theridiidae, this small to medium-sized spider—females reaching 5–8 millimeters, males somewhat smaller—constructs the characteristic messy, three-dimensional cobwebs in sheltered corners of buildings, under eaves, in cellars, and in other human-modified structures worldwide. Originally native to North and South America, the species has spread through commerce and human transport to Europe, Asia, Africa, and beyond, where it thrives in the stable temperature and prey-rich conditions provided by human habitation. The web design is deceptively effective: irregular sticky threads radiate in all directions from a silk retreat, ensnaring flies, mosquitoes, ants, and other arthropods that blunder into the structure. Females are long-lived—surviving several years—and produce multiple egg sacs containing hundreds of eggs during a lifetime, contributing to the species' population resilience. Parasteatoda tepidariorum has become an important laboratory model organism for arachnid developmental biology, with its genome sequenced to facilitate studies of spider gene expression, venom evolution, and silk production. It is broadly classified as Least Concern given its cosmopolitan distribution and remarkable adaptation to anthropogenic environments.

Shared Countries

Both species can be found in 1 countries:

🇺🇸 United States