Golden Orbweaver snares Horse Fly. Also Filmy Dome Spider

Black and Yellow Orb Weaver (male and female?)
Location: Milton, DE
August 7, 2011 9:27 pm
Heya Bugman!
My boyfriend and I found this gorgeous Orb Weaver while vacationing in Delaware this weekend. While we were taking photos of her, that black flying insect (any idea what it is?) got caught in her web. She was lightning-fast and had him wrapped up in seconds! A few hours later, we saw her snacking on her tasty meal. Bug on bug carnage!
We also caught a glimpse of a smaller spider nearby with similar coloring. The male, perhaps? Hoping you can identify that guy for us! Thanks!
Signature: Bruce and Ren

Hi again Bruce and Ren,
The Black and Yellow Orbweaver, Argiope aurantia, has several other common names and we generally prefer the name Golden Orbweaver.  That Fly looks awfully familiar, but we have been unable to correctly identify it at the time of posting.  It doesn’t match any of the Horse Flies we checked on BugGuide, nor could we match it to any Mydas Flies.  We will continue to research its identity.  We cannot say for certain if the smaller spider is a male, but this large female Golden Orbweaver looks to be filling with eggs.

As we were responding, we noticed you sent additional images and the smaller spider does appear to be a male Argiope aurantia.

Eric Eaton assists with Horse Fly identification
Daniel:
It is definitely a large female horse fly, maybe Tabanus atratus.  The “white” abdomen could be an artifact of the reflection of intense sunlight.
Eric

Hey again Daniel!
Horse fly makes definite sense to us. They’re everywhere near the beach in Delaware, as my very bitten up legs and arms can attest to!  And Eric’s theory of intense sunlight is spot-on.  Another picture we have shows nothing but black on the abdomen, so it’s entirely likely that I just caught the right angle to have the sun shining off the shiny part of the fly’s abdomen.  As for the spiders, we’re shocked!  We were speculating that it might be the male due to the similar coloring, but he was so small we nearly missed him and his web.  It’s hard to believe such a large spider and such a tiny spider are different genders of the same species!  Do the males make the stabillimentum as well?  We didn’t notice one in his web.  We really appreciate your help with identifying our interesting critters.  And thanks again for your amazing website!
Bruce and Ren

Hi again Bruce and Ren,
This BugGuide image nicely illustrates the size difference between the sexes of the Golden Orbweaver.  In most species of Orbweavers, the female is the larger of the pair, and in some species the size difference is noticeably great.  We have not seen any photos of male Golden Orbweavers with a stabilimentum.

Correction:  September 30, 2012
We just received a comment that made a correction to part of our identification.  The spider we believed to be a male Golden Orbweaver is actually a Filmy Dome Spider, Neriene radiata, which we verified on BugGuide, especially this image.