What kind of insect is this

I saw this thing in my yard today it looked as if it was spraying something on my tree, It is huge and Im curious if it is poisonous or anything like that can someone please let me know what it is and what it can do? here is the link to a pic of it. 10points with the info =)

http://www.flickr.com/photos/58378023@N03/6067218922/in/photostream

That would be an Ichneumon Wasp...

http://tinylittlelife.org/?p=180

It looks dangerous!!! Most poisonous bugs have bright colors like yellow and black, just like the bug you saw. You should squish it!!!