Haha, to be honest that's what I pictured in class when we were talking about it. I avoided describing it on the exam though for obvious reasons.
And damn...my brain has obviously dimmed some as well seeing as how I just wrote a huge explanation for a question that you didn't actually ask. The much simpler answer to the actual question you asked is no, they do not extend their proboscis when they land on anything. But they do extend it every time their antennae encounter sugary/sweet foods.
Dennis