Everybody who has exercised in short sprints has used their phosphagen system. This system provides the quickest route to producing energy, in the form of ATP, without oxygen consumption. Both vertebrates and invertebrates have forms of this system; creatine phosphate in vertebrates and phosphoarginine in invertebrates. Phosphoarginine plays an important role in maintaining cellular energy levels by providing a buffer during periods of energy fluxes and low ATP supply. Therefore, it is employed during periods of low oxygen availability. In Schistocera americana, growth occurs from one instar to the next; however, it also occurs within an instar. During this intramolt period, the relative tracheal system decreases in size. It is thought that this is due to the rapid expansion of tissues while the peripheral structures remain stationary. Assuming the atmospheric oxygen levels remain the same in the grasshopper’s environment, in the later stages of an instar it will no longer be able to obtain as much oxygen, and ATP production from aerobic respiration will decrease. To determine if late stage grasshoppers relied more on their phosphagen system, I measured levels of phosphoarginine and arginine at the beginning and end of the 6th instar. This was done using reverse phase liquid chromatography mass spectrometry (LC-MS). I hypothesized that animals in the later stages of an instar would have a higher concentration of arginine than animals in the early stages of an instar, indicating that the consumption of phosphoarginine to produce ATP increases in later stage grasshoppers to compensate for a decrease in aerobic respiration.