Non-stucco block walls are very common in the southwest; and they are typically constructed with expansion gaps at intersections and at support towers. These gaps provides scorpions (and their prey) great places hide during the day.
While you’re hunting, be sure to check corners and tower-gaps because you’ll often find scorpions hanging out nearby. If you DO see one, be prepared to move quickly because they will often dart back into the gap at the first sign of danger.