Neoscona oaxacensis

Current valid name

Neoscona oaxacensis (Keyserling) (family Araneidae)

Recognition and diagnostic features

Large bulbous abdomen, many spines on its legs. Lateral eyes very far from median eyes. Much variation in coloration, ventral surface of abdomen with central black square bordered laterally by 4 white dots or 2 comma-shaped marks, often has coffee bean pattern on dorsum of abdomen.

Related or similar species

Metepeira arizonica

Spider

Body lengths when mature: male: 6.3 - 12.7 mm, female: 8.9 - 18.0 mm

Although immatures should resemble mature adults, there is tremendous variation in coloration that can cause uncertainty.

Egg sac

Description: Loosely made egg sac in a cavity of a folded leaf, massive number of eggs neatly arranged in a tight pattern, eggs not loose like in other sacs, 14.4 ± 3.1 mm wide, 20.6 ± 1.0 mm long

Number of eggs per sac: 898 ± 141.6

Size of egg: 0.81 ± 0.051 mm

Time of year eggs are likely to be laid: July for first generation, September to October for second generation after the harvest season is mostly over

Distribution

In California: throughout much of the state

Elsewhere: southwestern U.S. states through Central America into Peru

Native to North America

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

Biology

Nocturnal orb weaving spider, often stringing a large orb web between rows such that field workers put sticks on their tractors to intercept the webs and knock the spiders down. Hides in grape bunches. May have two generations in the Central Valley, which is atypical for the species (usually one generation per year). Generally completes life cycle in about 6 months then dies by winter. Can be very large.

Status in table grapes

Level of Incidence: common

Level of Concern in New Zealand: WPNZ (May 2010) nr, BORIC (Dec 2011) R, MAF-BPRA (2002) nr (coding definition)

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

Level of Medical importance: minor, however, because it is a large spider, a bite would be painful due to mechanical fang penetration of skin

Common name

Western garden orbweaver for species, orb weavers for family

Taxonomic history

Fairly stable, especially considering the amazing coloration variations this spider can exhibit.

Selected references

Berman, J. D., and H. W. Levi. 1971. The orb weaver genus Neoscona in North America (Araneae: Araneidae). Bull. Mus. Comp. Zool. 141: 465-500.

Pascoe, F. H. 1980. A study of Neoscona oaxacensis (Araneae: Araneidae) in commercial avocado orchards in San Diego County, California. Calif. Avocado Soc 1980 Yearbook 64: 153-186.