Uloborus diversus

Distinguished from other orb-weaving families by the presence of a cribellum and calamistrum (cribellate silk production system) versus the sticky, glue-studded silk of ecribellate orb-weavers. Within Uloboridae, U. diversus is separable from congeners by its desert distribution and typical brown coloration with longitudinal abdominal mottling; however, considerable phenotypic variability has led to many junior synonyms. The reduced, horizontal orb web with possible linear or auxiliary spiral stabilimentum differs from the triangular sector webs of Hyptiotes. Examination of male pedipalps and female epigynum required for definitive species identification.

Desert regions of the southwestern United States and Mexico. Constructed webs have been observed in greenhouses, at culvert openings, and in various outdoor situations suggesting adaptability to human-modified environments within arid zones.

Southwestern United States and Mexico. Records from Mexico and USA (GBIF).

Females construct small, flattened, papery egg sacs typically positioned near the periphery of the web; multiple sacs may be arranged in a row. Spiderlings hatch and immediately build orb webs, but these differ from adult webs: they possess additional radii and retain the auxiliary spiral at the hub because hatchlings lack cribellum and calamistrum. After the second molt, spiderlings develop these structures and transition to "normal" cribellate web architecture.

Constructs relatively small, horizontal orb webs that may incorporate a stabilimentum—either as an auxiliary spiral or a linear band through the web center. Lacks venom glands; subdues prey through extensive silk wrapping and constriction that compresses softer body parts and may break appendages, potentially causing asphyxiation as silk dries and tightens. Web construction is slow and methodical, with cribellate silk drawn through the cribellum and "fluffed" using the calamistrum.

Predator of small flying insects; cribellate silk may incidentally capture larger insects (such as butterflies in greenhouse environments) without successful subjugation, potentially interfering with their flight and feeding.

Important model species for scientific research on spider silk protein (spidroin) evolution and the neurobiology of orb-web building behavior. Subject of a 2.15-Gbp chromosome-level genome assembly. Non-venomous; harmless to humans.

• Hyptiotes cavatusAlso in family Uloboridae and lacks venom glands, but constructs triangular sector webs rather than complete orbs, and is primarily eastern North American in distribution.
• Uloborus glomosusCongeneric cribellate orb-weaver with similar morphology and web structure, but differs in geographic distribution and specific genitalic characters; males are rarely observed.
• Argiope spp.Ecribellate orb-weavers that construct webs with stabilimenta, but use sticky glue-studded silk rather than cribellate hackled silk, and possess venom glands.
• Cyclosa spp.Ecribellate orb-weavers that may incorporate stabilimenta and debris into webs; differ in silk type (sticky, not cribellate) and presence of venom.

• cribellate
• orb-weaver
• non-venomous
• model organism
• desert
• genome
• neurobiology
• silk
• Uloboridae
• hackled orb-weaver
• stabilimentum

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Bembicid Holdings | Entomology Research Museum
• Bug Eric: Spider Sunday: Featherlegged Orb-weavers
• Bug Eric: Spider Sunday: Triangle Spiders
• A three-dimensional immunofluorescence atlas of the brain of the hackled-orb weaver spider, Uloborus diversus.
• A three-dimensional immunofluorescence atlas of the brain of the hackled-orb weaver spider, Uloborus diversus.