Question
QUESTION: I have four bugs that look like caterpillars.  They are about 1/2 in long with ecru hairs or horns at both ends and the body are green with a red mark in the middle of it. They are on the underside of the leaf.

ANSWER: There are hundreds of different looking caterpillars in many different parts of the world. As I don't know where you garden, I wouldn't be able to tell you what it is. If it isn't eating the leaves then it is a good bug.

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QUESTION: I live in Virginia Beach, Virginia. I am suspecting that they may be gypsy moth larvae but cannot be sure.  The leaf I put in with  them in a jar is totally consumed.  Your thoughts.  Thank you!.

Answer
Gypsy moths are leaf eaters, and though they only feed for about 40 days, the results can damage a lot. They prefer Oak leaves, but they can survive on many other types of tree and shrub leave and will eat  anything that is green. Gypsy moth caterpillars feed at night to avoid being preyed upon by birds. During the day the caterpillars crawl down the tree to hide, and this is when they are most visible to humans. When populations are high, gypsy moth caterpillars feed non-stop, day and night. They take about 40 days before they spin a cocoon to become a moth. You might be wise to check and see what else they are munching on in your garden. Here is a photo and info on the gypsy moth caterpillars.
http://en.wikipedia.org/wiki/Gypsy_moth