A previous study of the crab spider Misumenoides formosipes showed that males guard immature females that are close to their adult molt. The limited number of immature females relative to the number of searching males, results in male-male conflicts to gain access to mates. Game theory, as applied to animal conflicts, predicts that opponents will settle contests without further escalation by assessing asymmetries in resource holding power. Size asymmetries are considered to be a likely cue for such assessments. In staged contests on flowers between differently-sized opponents, large males displaced smaller guarding males in 80% of the trials, with little or no escalation. Males sometimes used leg autotomization as a means of escape from opponents. In staged contests between equally-sized males, one if which was missing a raptorial front leg while the other had its legs intact, the two types of males won with equal probability. Analyses of ice. formosipes behavior have been based on the assumption that they exhibit first-male sperm priority. I describe preliminary work using a unique application of DNA fingerprinting technology to test that assumption.