Theridion melanurum
adult female, live |
adult male, live |
adult male, dead |
female genitalia; epigynum |
male genitalia; palp, lateral view |
male genitalia; palp, ventral view |
grape size comparison with adult spiders; male (left), female (right) |
spiderling, live |
spiderlings, dead; dorsal (left), ventral (right) |
egg sac |
egg sac with scale (cm) |
eggs |
Current valid name
Theridion melanurum Hahn (family Theridiidae)
Recognition and diagnostic features
Small, dark brown with globose abdomen.
Related or similar species
Theridion dilutum, immatures of Latrodectus hesperus, Cryptachaea porteri.
Spider
Body lengths when mature: male: 2.8 - 4.6 mm, female: 3.0 - 4.8 mm
Immatures resemble miniature adults.
Egg sac
Description: spherical ball of bicolored tan-brown eggs very loosely covered with tannish silk, egg sac color caused by egg color, 3.06 ± 0.52 mm diameter
Number of eggs per sac: 57.91 ± 36.75
Size of egg: 0.55 ± 0.027 mm
Time of year eggs are likely to be laid: prior to harvest season
Distribution
In California: mostly along coastal regions throughout state
Elsewhere: eastern half of Washington and Oregon, British Columbia, Europe, North Africa, Siberia
This may be a naturally Holarctic species, and may be native to North America.
This species may not have been transported or become established outside of its range, but it is unclear whether it is a naturally Holarctic species.
Biology
Small cobweb weaving spider. Makes webs on grape leaves. Found in grape bunches. Female guards egg sac.
Status in table grapes
Level of Incidence: very 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: none
Common name
None for species, combfoot spiders for family
Taxonomic history
Stable
Selected references
Levi, H. W. 1957. The spider genera Enoplognatha, Theridion, and Paidisca in America north of Mexico. Bull. Amer. Mus. Nat. Hist. 112: 1-124.