Pupae of Aedes triseriatus were collected from discarded automobile tires and trees holes in St. Joseph Co., Indiana. Peak pupation occurred about 2-3 weeks earlier in discarded tires than in tree holes, probably due to the higher water temperatures in tires. Unshaded and shaded tires produced 42% and 133% as many males and 20% and 91% as many females as tree holes, respectively. There was a decline in body size of adults from shaded tires towards the end of the summer, probably owing to depletion of nutrients and thus increased intraspecific larval competition. Transovarially infected females emerging from discarded tires may initiate La Crosse encephalitis virus amplification as much as a month earlier than females from tree holes.