The narrator notes that lots of people don't believe in curses or yellow-spotted lizards, but in the case of the lizards, it doesn't matter if you believe or not if one bites you. The narrator explains that the yellow-spotted lizards are named for their spots, though the spots are their least obvious feature. They're between six and ten inches long with red-rimmed, yellow eyes. They have black teeth and white tongues. If anyone gets close enough to see the spots, they're as good as dead. The lizards live in holes and leap out to attack live prey. They also eat the shells of sunflower seeds.
The yellow-spotted lizards are another way that the novel suggests that nature requires respect: the lizards require humans to understand that they're dangerous and not to be messed with if they mean to survive. The mention that they eat sunflower seeds casts Mr. Sir's habit of spitting seeds into holes in an especially sinister light. Though it's unclear if he knows this, he is definitely attracting lizards to where the boys are digging.