There are many different species, but flea beetle adults are small (about 0.125 inch or 1 mm long), shiny, hard beetles with enlarged hind legs that allow them to jump like fleas when disturbed. Different species vary in color and markings.
Adults do most of the damage by feeding on leaves, creating holes. Most serious damage is done when plants are seedlings; older plants are more tolerant although outer leaves can show damage.
Read more about flea beetles.
Leafminer adults are small black and yellow flies. Larvae are yellowish maggots that feed beneath the leaf surface leaving tunnels.
Read more about leafminers in the vegetable garden.