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Leucauge venusta (Walckenaer) - Leucauge argyrobapta

Leucauge venusta (Walckenaer) - Leucauge argyrobapta
Zimlich Zone, Mobile, Mobile County, Alabama, USA
July 29, 2012
Leucauge venusta (Walckenaer)
Det. Lohn and Jane Balaban, 2012

Coll. sweeping during BG Gathering_2012
Spmn deposited in the TAMUIC

Any thought that
this might not be a Leucauge? My spider expert here in Kansas thinks it is not that genus at all, but is also not sure what it is. If it is well under 5 mm his guess is a member of Theridion or related...but cautions that group has been subdivided recently into more genera. It is a beautiful specimen!

Maybe the female indication on this specimen threw him? I don't see how we can know whether this is male or female at this instar. Were this a known female at under 5mm, I'd agree that it couldn't be L. venusta.

Mike, just FYI, it is typical for immature spiders to resemble the adult female, but for adult males to suddenly take a different pattern with the penultimate or final molt.

Don't know how well your expert can see the image,
but we can clearly see the proximal cluster of trichobothria on femur four that is the hallmark of this species for us. Hadn't heard that other species have that, but...

Yup, Leucauge
Agreed. I didn't notice the trichobothria earlier. I had to drop a det label in one of these today and found myself confirming the diagnosis first. According to Levi's 1980 paper revising various subfamilies of 'Tetragnathinae': "Close to Leucauge are two genera, Alcimosphenus (with two species in the West Indies) and the neotropical Mecynometa. Both also have the rows of trichobothria on the fourth femur." Platnick's catalog does not report either of these last two genera to occur in the U.S.

That leaves us with L. venusta or L. argyra, the latter of which is only reported from Florida. Curiously, SONA indicates that there is only one species of Leucauge in the U.S., L. venusta, while at the same time indicating that Levi's 1980 paper is the most recent revision for the species, and that paper distinguishes L. venusta and L. arygra from Florida.

I think the only room for doubt comes from the fact that these keys are made to work for adult specimens, not juveniles, so it's possible that a closely related genus could also exhibit these characters as juveniles but not as adults. If I knew of even one photo that gave a good explanation for how they knew a spider with this abdominal pattern was a juvenile L. venusta, I'd be 100% convinced of the placement in Leucauge, giving a much higher probability to L venusta over L. argyra. (I wish BG let us filter by det method - e.g. demonstrated offspring of definitive L. venusta.)

We don't know when Plesiometa
got put back into Leucauge. There was certainly a time when we had one species of Leucauge, L. venusta, and one species of Plesiometa, P. argyra. But now they are both Leucauge and we're not sure when that happened relative to the publication of the SONA manual. We certainly had argyra here on BugGuide under Plesiometa for a number of years.

I don't know one from another. Maybe Mike could take a closer look at the specimen under a microscope. It could very well be the species listed, just wanted to bring up the possibility. :-)

I'm open to all suggestions...
Thanks, Mike

Moved - it does resemble Leucauge venusta...

Leucauge venusta - female
Note the dark edging to the carapace...

May actually be Tetragnathidae
Leucauge venusta

but we don't know how to confirm that :(

Interesting that! It looks identical to the 2nd thumb you posted. How did we come to know that this is the immature L. venusta pattern? It makes sense that Theridiids and orbweavers could look so similar as immatures -- Theridiids evolved from orbweavers.

Moved from Spiders.

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