Please help with insect identity.

[The Backlash Cometh]

About the same place where I was attacked by a couple horseflies a month ago, I saw a strange insect collecting what looked like green caterpillars and depositing them in a crevice between two rocks. What surprised me was how efficiently she was collecting the caterpillars. In a period of five minutes, she had brought three victims into her lair and left to get more. Unfortunately for her, it was bad timing because I was working the area and I knew that she was on a fatal collision. Let's just say that by the end of the day, the flying insect was dead. Not my choice, but, it was something I couldn't avoid. Anyway, I was curious if the bug was the reason why my gulf fritillery caterpillars are disappearing from the vine. The insect is all black and isn't as long as a wasp. Its body was rich with yellow pollen. What was it and what were the green caterpillars or green tube-like larvae it was carrying?

Oh, and would horseflies ever make a home out of a crack between two rocks?

[Blue Gardener]

1. Can you get a picture?

That might help. There is insect identification information on the Iowa State extension service website that might help. I'll see if I have time to look over the weekend.

[Blue Gardener]

2. Can't find it on the Extension Service website

But I ran across this website that might be helpful:

http://www.whatsthatbug.com/index.html