The scorpion is the crest of the Alacrán family. Family crests hark back to antiquity (just think of medieval knights or feudal landlords), and yet today many groups (good and bad) have logos and families have a crest that has symbolic meaning for their house or family. So In The House of the Scorpion, the word ‘house’ refers to the Alacrán family, while the actual scorpion is the symbol that El Patrón has chosen to represent that family.
The question may come up in the reader’s mind as to why the scorpion was chosen by El Patrón to represent his family in the first place. After all, scorpions are not usually viewed in a positive light as they can be quite dangerous due to being venomous (which can be lethal, depending upon the species). Scorpions are often associated with desert regions, and Opium is situated in a desert. The scorpion is therefore an appropriate symbol for El Patrón – a dangerous, desert creature.