Blood feeding insects such as the “kissing bug”, Rhodnius prolixus create a high volume of oxygen radicals when the blood meal is metabolized. Oxygen radicals can damage cell membranes if in high enough concentration and must be neutralized. The neutralization process involves the reaction of the oxygen radical with an oxygen scavenger.
Mammalian blood contains copious amounts of the protein hemoglobin. Metabolism of the protein creates nitrogenous waste that can be excreted in the form of uric acid but some is retained. Uric acid is a scavenger of oxygen radicals. Rhodnius maintains high levels (about 5 mM) of uric acid in its hemolymph. Uric acid is responsible for neutralizing almost all of the oxygen radicals. The product of the reaction of oxygen with uric acid can be excreted. Using uric acid for protection against oxygen radicals makes certain that not all goes to waste.