Like all true bugs, ambush bugs undergo simple metamorphosis, from egg through nymph and adult stages. Clusters of eggs are laid by overwintered females when the weather warms in springtime.  After hatching, nymphs undergo from 4-7 molts, shedding their exoskeleton as they grow, eventually reaching the adult stage.

Ambush bugs are often lumped in with another family, the Reduviidae, which are commonly called Assassin Bugs. Both Phymatidae and Reduviidae are distinguished from other families by their short, 3-segmented rostrum (rostellum), or beak. The beak is used variously to pierce, inject poison into, and suck juices out of prey. Bugs in other families have 4-segmented rostrums more often adapted to simply sucking fluids from plant tissue.

Ambush bugs can fly, but do so poorly, and generally only between adjacent flowering plants. I've never seen one do it.

There is anecdotal evidence some bugs in these two families can inflict painful bites on humans; in particular, the wheel bug, so-called for the peculiar structure on its thorax resembling an involute gear or radial saw blade.  (I can't help but wonder if this common name only evolved after the invention of those two somewhat esoteric items.)