It turns out to be the larva of a lacewing. This what the adult looks like.
The larvae have powerful jaws that are hidden under the bits of debris that they stick to their back. They have been observed sticking bits of the animals they consume onto their backs in order to infiltrate undetected the places where these bugs are found. Here is a newly-hatched larva before it begins to stick on its camouflage. The things that look like antlers are really its jaws.
The larvae are considered beneficial insects as they feed upon insects that are destructive to crops and garden plants. They are especially fond of aphids.