The leaves of the carnivorous Sarracenia purpurea (Purple Pitcher Plant) provide habitat for obligate insects. Within the pitchers of this plant, Metriocnemus knabi (Pitcher Plant Midge) larvae coexist with Wyeomyia smithii (Pitcher Plant Mosquito) larvae. No other mosquito species has been reported to utilize this habitat in the presence of the midge. We tested whether the midge larvae were responsible for the elimination of other mosquito species. We introduced 1 Aedes triseriatus (Eastern Treehole Mosquito) larva, into each of 90 different pitchers. After 45–75 minutes, we extracted the fluid from the Purple Pitcher Plant and counted mosquito and midge larvae. Although 98% of pitchers contained Pitcher Plant Mosquito larvae, we did not detect 61 of the Eastern Treehole Mosquito larvae. Of the 29 surviving introduced larvae, we found 13 (45%) in pitchers that had no midge larvae. Drier than normal conditions in 2012 provided the opportunity to investigate Purple Pitcher Plant leaves devoid of water and obligate insect larvae, and the potential for foreign mosquito larvae to colonize unoccupied pitchers. We found Pitcher Plant Midge or Pitcher Plant Mosquito larvae within 13 days following the addition of water. We observed no foreign mosquito larvae. The inquiline larvae did not develop when we added water to dry pitchers in the laboratory, suggesting that oviposition by Pitcher Plant Midge and Pither Plant Mosquito adults occurred after a rainfall event. During dry conditions, shaded Purple Pitcher Plants retained some fluids, and adults likely completed their life cycle in these plants. However, severe, prolonged drought may eliminate Purple Pitcher Plant inquilines and potentially make the pitchers available for exotic mosquito larvae.