House crickets were hypothesized to have a higher metabolic rate than sand fiddler crabs, indicated by higher CO2 production. However, experiments measuring CO2 levels from samples of each species found that crickets produced significantly more CO2 per gram than crabs over three six-minute tests. This refuted the hypothesis and suggested crickets have a higher metabolic rate and energy needs than crabs. Limitations included a small sample size and potential stress from prior handling of test animals.