Just using this as a place to gather my thoughts for now, based on
digitallibrary.amnh.org - PDF Article, The fulva group of the spider genus Steatoda (Araneae, Theridiidae). Gertsch, 1960.
biodiversitylibrary.org - PDF Article, Spider Genera Crustulina and Steatoda. Levi, 1957.
albomaculata - Southern Canada to central Mexico.
grossa - coastal species, purplish abdomen
transversa - southern CA, AZ & TX, Carapace, legs orange-brown. Abdomen purplish with white spots. Closest pattern/image we have to the drawing is
triangulosa - Widespread in the United States.
S. variata - UT, AZ, CO, NM, western TX, Mexico. Pg. 26 Gertsch 1960. We are going to have issues separating this from A. pulcher where they overlap in AZ. The leg banding in A. pulcher may be key, but not sure at this point. - Pattern variable, color variable (orange carapace & reddish abdomen in UT, AZ and southward reddish brown carapace with blackish abdomen), a single median row of large dorsal spots (with small frontal paired ones often absent) separates this from the similar S. punctulata, longer legs in both sexes. Also easily mistaken for S. washona, but S. washona is a foothill/mountain species while S. variata is a desert species. The two spotted variation is found in the eastern range and the mid-dorsal spotted variation is found in the west. Best match I can find to the mid-dorsal spotted variation in Levi 1957 is
The best matches for Gertsch, 1960 are
(but not supposed to be found in CA) So what is that?
- variata china - very southern tip of TX
S. variata - Males resemble females but the spotting on the abdomen becomes indistinct in masculine males.
A. americana -
A. fulva - Pattern stable, species abundant & widespread. Very similar to A. pulcher. First spot is longer than wide in A. fulva & wider than long in A. pulcher.
A. medialis - misidentified in Levi 1957 (actually S. variata). See pg. 9 of Gertsch 1960. One variation of S. variata looks like A. medialis with the paired dots at the top of the mid-dosal spots. However, the paired spots appear to be smaller and higher in A. medialis. Also A. medialis only has one pair of paired spots while S. variata may have multiple pairs. Closest image we have that match Gertsch's drawings are:
A. pulcher - Relatively large spots of the middle line form a distinct band in average specimens, sometimes the white may take over the entire abdomen. Bright orange to dusky brown carapace with dusky radiating lines. Legs may show bands. Abdomen varies from reddish to black. The frontal spot is present, but never paired as in S. variata.
A. americana - Fairly distinct compared to the other species.
A. fulva - Pattern stable, species abundant & widespread.
A. medialis -
A. pulcher - Males usually have black abdomens with distinct narrow, dentate band running back to caudal end, but the side spots are usually reduced or missing.