If you are seeing black and red bugs scurrying about near trees and buildings, they may be boxelder bugs. Boxelder bugs (Boisea rubrolineata) feed on the flowers, leaves and seedpods of female boxelder trees (Acer negundo) and occasionally are found on maple and ash, and sometimes on certain stone fruits and grapes.
Boxelder bug adult and nymphs. [J.K.Clark]
Boxelder bugs are often confused with other insects that look similar such as red-shouldered bugs, squash bugs, the bordered plant bug, and leaffooted bugs.
This insect doesn't usually cause significant damage to landscape plants, but when their numbers are high during fall, they can build up on outside walls or sometimes enter houses and may be considered a nuisance.
If you have a large spring population in your landscape, follow UC IPM's preventive practices now to stop them from becoming a problem later. Consult the UC IPM Pest Note: Boxelder Bug for more information.
Adult red-shouldered bug. [J. Gross]