Lookalikes
for Boxelder Bug
The closest twin is the western boxelder bug (Boisea rubrolineata), a nearly identical western species that also bears three red thoracic lines and gathers on homes in fall; range usually separates the two. Against other red-and-black insects, those three lengthwise thoracic lines are the reliable giveaway. Source: https://ipm.ucanr.edu/PMG/PESTNOTES/pn74114.html