Uloborus diversus

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Current valid name

Uloborus diversus Marx (family Uloboridae)

Recognition and diagnostic features

Uniquely shaped abdomen, makes orb-web in horizontal or slanted plane.


Body lengths when mature: male: 2.4 mm (range 2.1 to 2.7), female: 4 mm (range 3.2 to 4.7)

Immatures resemble miniature adults.

Egg sac

Description: suspended in web, very odd shape with projections around perimeter and little spicules attached to surface, looks like a tanned cowhide or the cell body portion of a neuron

Number of eggs per sac: 29.8 ± 15.3

Size of egg: 0.74 ± 0.028 mm

Time of year eggs are likely to be laid: found in April


In California: most of state except northern counties

Elsewhere: Arizona, Utah, Nevada. Mexico

Native to North America

This species has not been transported or become established outside of its range.


Orb weavers. Often found around and inside homes. Often make a horizontal or slanted orb web, unlike the typically vertical orb web of the Araneidae. Extremely rare in grapes.

Status in table grapes

Level of Incidence: very rare

Level of Concern in New Zealand: WPNZ (May 2010) nr, BORIC (Dec 2011) nr (not listed), MAF-BPRA (2002) nr (coding definition)

Level of Concern in Australia: WPAU (2006) nr (coding definition)

Level of Medical importance: none, this is one of the unique spider families lacking venom glands

Common name

None for species, hackled orbweavers for family

Taxonomic history


Selected references

Muma, M. H., and W. J. Gertsch. 1964. The spider family Uloboridae in North America North of Mexico. Amer. Mus. Novit. #2196, 43 pp.