if that spider bagged that fly from it's web it is an awesome demonstration of how venom can be quite toxic to inverts and pose no danger to verts. it is sometimes hard for me to convey how complicated the whole venom situation is
Yeah, I see what you mean. From that angle it sort of does resemble a Zygiella.
These immature A. marmoreus are all over my yard, and some adults are out now, too. The big ones tackle equally large prey. I usually see them wrap up whatever falls into their web, but I came across one large adult female that had a big bumblebee by the back of the thorax. The bee was unwrapped and struggling, but the spider held on until it stopped moving.
Here's a picture of it (a little blurry, because I didn't use a flash and the struggling bee and a slight wind caused the web to sway a bit):
Normally, as you know, an orb weaver will spin its prey like a top between its back legs and wrap the prey as it goes around and around. What was funny about the little spider in the top picture was the fly was too big for this, so the spider was running circles around the fly, sort of like a hamster on a treadmill, in order to wrap it up! Too bad I didn't get that on video.