Insect Floral Visitors of Ptelea trifoliata (Rutaceae) in Iowa, United States

Ptelea trifoliata L., is a North American tree that supports insect communities through floral rewards. Our objectives were to determine the importance of insects as pollinators of P. trifoliata; describe the community of floral visiting insects of P. trifoliata in Iowa, where no such information was available; and to note insect preferences for male or female flowers. Over two years, inflorescences on 13 trees were covered with mesh bags before blooming and the amount of fruit produced was compared to uncovered inflorescences from the same trees. In one year, insects were collected from male and female trees with an insect vacuum every 3 h between 7 am and 7 pm from four sites in Iowa, USA between 30 May and 16 June 2020. In 2019 and 2020, almost no fruit set occurred from inflorescences covered with mesh bags while an average of 51.2 fruits formed on unbagged inflorescences (P < 0.0001), suggesting insects larger than the 600 µm pore diameters mesh were responsible for pollination of P. trifoliata. Insects from five orders, 49 families, and at least 109 species were collected. Most insects were Hymentoptera (48.3%) or Diptera (28.2%). Male flowers attracted 62.3% of all insects collected. Since most of the insects found visiting P. trifoliata were not bees, the floral rewards of the flowers may be a valuable resource for a wide variety of insects in the central United States.