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For Insects, Spiders & Their Kin
For the United States & Canada
Anterodorsal view - Theridion murarium - female

Anterodorsal view - Theridion murarium - Female
Spring Creek (between 1st and 2nd bridge), Pennington County, South Dakota, USA
June 24, 2009
Size: 4.0 mm

Images of this individual: tag all
Anterodorsal view - Theridion murarium - female Ventral view of abdomen - Theridion murarium - female Dorsal view - Theridion murarium - female

Do you know if this species ranges south to FL?

Hi Jeff,

Yes, it's a truly widespread species, found throughout North America, even in Mexico --- "southern Canada south to Chiapas ... most common in eastern United States," Levi (1957a) writes; his map indicates several records for Florida (all on the Gulf side, for whatever reason).

Kaston writes that it is less common than differens, but that the three (differens, murarium, and glaucescens) are all very similar in size and abdominal pattern. Levi shows a similar distribution for differens and glaucescens, again with an eastern concentration (and including Florida).

I'll add one more image today.

have this species (or one maybe of the others you mentioned) around the house. Color and pattern very similar.

Anyway, this past August I witnessed an adult female feeding on a subadult L. geometricus! It seems their webs were adjacent, and the Theridion acted in the same manner as an Argyrodes when they subdue the host of a web while the host is feeding. The brown widow was busy consuming a cricket, and it must not have noticed the intruder. The Theridion was feeding from the widows hind leg, and did not even wrap it up. It is likely this could have been an act of desperation from a starving Theridion. I'm just baffled that the widow fell victim to it... and banging my head against the wall for not taking a picture even though I was on my way out.
That might have been a once in lifetime thing for me, but as long as both species stick around here, maybe I'll get lucky...

"Beware the cobweb spider..."
How did they compare by size?

sorry for the delay.

The widow was around 9mm BL, and the Theridion BL~4mm. There was a significant difference in size.