Symbols are objects, characters, figures, and colors used to represent abstract ideas or concepts.
Onions symbolize a positive and healing factor in the novel. Sam, a character of good will and intelligence, loves onions and helps to cure sick people with the onion remedies that he makes. The onions allow Stanley and Zero to regain their health and rest before attempting to break free of the oppression of Camp Green Lake. The onions also help Stanley and Zero avoid bites from the deadly yellow- spotted lizards that frequent Camp Green Lake.
Yellow-spotted lizards represent the deadly aspects of Camp Green Lake. They invaded the area after the life-giving lake dried up and they present a deadly threat to all humans at the camp. It was a yellow-spotted lizard that killed Kate Barlow and it is yellow-spotted lizards that threaten Stanley and Zero while they are digging for Stanley's great-grandfather's suitcase. The reason Stanley and Zero survive is because they have eaten so many onions (a positive and life-affirming symbol) that the lizards, who do not like onion blood, do not wish to bite them.
The boys at Camp Green Lake are made to dig holes in the desert sand all day under the hot sun, and their fruitless labor mirrors that of a prison system. The officials at the camp claim that the juvenile delinquent campers are digging to “build character” and teach them discipline, but unbeknownst to the boys, they’re really searching for Kissin’ Kate’s treasure. The boys are not, in fact, learning to improve themselves or become better members of society at Camp Green Lake. They’re doing free work for The Warden, who set up the camp as a scheme to attract unpaid labor for her own nefarious purposes. Camp Green Lake is a microcosm of the carceral state, and the holes that the boys are made to dig represent the penal labor that prisoners are forced to do as part of their sentences. That labor is not only often underpaid or completely unpaid, but it does little to help reform prisoners or prepare them to integrate back into society as better-functioning community members. Just like prisoners are used for free labor, the boys of Camp Green Lake are used as treasure hunters, and none of the staff at Camp Green Lake actually care about reforming them.