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Genus Theridion

Theridion male - Theridion - male Spider - Theridion spider - Theridion - female Spider - Theridion Cobweb Spider - Theridion kawea - female Spider - Theridion albidum - female Theridion female - Theridion - female Unidentified tiny spider - Theridion
Classification
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Chelicerata (Chelicerates)
Class Arachnida (Arachnids)
Order Araneae (Spiders)
Infraorder Araneomorphae (True Spiders)
No Taxon (Entelegynae)
Family Theridiidae (Cobweb Spiders)
Genus Theridion
Numbers
65 species in our area(1)
Range
65 species in our area(1), but the world spider catalog lists the following 54. More detailed ranges will be given when time allows.

T. aeolium - USA
T. agrifoliae - BC, CA, OR, WA
T. albidum - AL, CT, IL, IN, KY, LA, ON, MA, MD, MO, MN, NJ, NY, PA, TN, VA, WI, WV
T. arizonense - AZ, NM
T. australe AL, DE, GA, LA, MD, MS, NC, NJ, TX, Mexico
T. californicum - BC, CA, OR, WA
T. cameronense - very southern tip of TX, Mexico
T. cheimatos - FL, GA, OH, TN
T. cinctipes - TX, Mexico
T. cochise - USA
T. cowlesae - southern CA
T. cynicum - TX, Mexico
T. differens - widespread across the US, Canada
T. dilutum - southwestern US - AZ, CA, NV, TX, UT, Mexico
T. dividuum - southeastern USA - AL, NC, SC, TX
T. dulcineum - AL, GA, MD, TN
T. ellicottense - USA
T. flavonotatum - southeastern US, AL, FL, GA, OH, KY, LA, MS, MD, NC, SC, TN, TX
T. frondeum - AL, BC, IA, IL, ND, NF, ON, QC, SK, TX, WA & the entire northeastern US
T. geminipunctum - very southeastern CA
T. gertschi - USA
T. glaucescens - LA, NE, TX, then WI south to MS & all the states east of that line, very southeastern Canada
T. goodnightorum - AZ, CA, CO, NM, TX, UT, WY, Mexico
T. hemerobium - CA, CT, IL, MA, MI, MN, NJ, NY, WI, very southeastern Canada
T. hidalgo - mid to southern TX, Mexico
T. intritum - USA - AL, FL, GA
T. istokpoga - FL
T. kawea - southwestern USA - CA, UT, Mexico
T. lawrencei - CA, ID, OR, WA
T. leechi - BC, CA, CO, ID, NV, OR, UT, WA, WY
T. leviorum - USA
T. llano - USA - central & southern TX
T. melanostictum - USA, Canada
T. melanurum - BC, CA, ID, OR, WA
T. michelbacheri - CA, MT, OR, WA
T. morulum = T. jeanae - AZ
T. murarium - widespread across the US, also in southern Canada
T. myersi - FL, TX, Mexico
T. neomexicanum - AZ, BC, CA, CO, ID, MT, NM, OR, UT, WA
T. neshamini - GA, IL, NC, PA, VA
T. orlando - FL, GA,
T. pennsylvanicum - AL, CT, FL, IL, MD, MO, NC, NJ, TN,
T. petraeum - Holarctic, mostly northern states - CA, WA, ID, ND, UT, CO, NE, NY, ME
T. pictum - Holarctic, across Canada & ID, MA, ME, MI, MT, NH, NY, SD, UT, WI, WY
T. positivum - very southern TX
T. punctipes - CA, OR, WA
T. rabuni - USA - CA, CO, DE, GA, MD, NC, NE, NJ, SC, SD, TX, UT
T. saanichum - coastal CA, OR, WA, AB, Alaska (mostly a coastal species)
T. sardis - USA - SC, GA
T. submissum - AZ, NM, TX, Mexico
T. timpanogos - UT
T. transgressum - AZ, CO, NM, UT, Mexico
T. varians - WA & BC
T. yuma - USA



Texas species:
T. australe Banks, 1899
T. cameronense Levi, 1957
T. cinctipes Banks, 1898
T. cynicum Gertsch & Mulaik, 1936
T. differens Emerton, 1882
T. dilutum Levi, 1957
T. dividuum Gertsch & Archer, 1942
T. flavonotatum Becker, 1879
T. frondeum Hentz, 1850
T. glaucescens Becker, 1879
T. goodnightorum Levi, 1957
T. hidalgo Levi, 1957
T. llano Levi, 1957
T. murarium Emerton, 1882
T. myersi Levi, 1957
T. positivum Chamberlin, 1924
T. rabuni Chamberlin & Ivie, 1944
T. submissum Gertsch & Davis, 1936
Remarks
One tropical species (T. nigroannulatum) is social, but it is found in Ecuador & Peru.

From Levi 1957a, the males with mastidia on the chelicerae just below the clypeus are:

P. pictipes
T. neomexicanum
T. californicum
T. frondeum
T. albidium
T. agrifoliae

T. albidium is mentioned as having a small mastidion, but in the second shot here it looks pretty big. Besides T. frondeum and P. pictipes, the others are more western in distribution. From the maps, T. frondeum seems to have the northern market cornered. The most northeastern data point for P. pictipes is in southern SC. ~ Kyron Sept. 16, 2013
See Also


Enoplognatha have the four bottom eyes almost straight across, with very little space between the top and the bottom eye rows. In Theridion, the bottom row have a slight downward curve, with more of a gap between the rows:
  Theridion           Enoplognatha


Also in E. ovata the carapace has a dark border line. That line is often missing in Theridion species.

  Arctachaea - Very round carapace


Print References
Levi 1957(2)
Internet References
Peggy Dorris Survey List - AR spp. with state records
digitallibrary.amnh.org - descriptions of edinburgensis, expulsum, cynicum, insulsum, realisticum, redemptum, detractum, & schullei
Works Cited
1.Spiders of North America: An Identification Manual
D. Ubick, P. Paquin, P.E. Cushing and V. Roth (eds). 2005. American Arachnological Society.
2.The spider genera Enoplognatha, Theridion, and Paidisca in America north of Mexico (Araneae, Theridiidae)
H.W. Levi. 1957. Bulletin of the American Museum of Natural History 112, article 1, 123 p.