While visiting Side Cut Metropark near Maumee, Ohio last month, I came across this common oblique syrphid fly (Diptera: Syrphidae: Allograpta obliqua) visiting a mullein foxglove (Dasistoma macrophylla, Scrophulariaceae). Like other adult syrphid flies, common oblique syrphids often feed on nectar and pollen. These common and widespread insects are regarded as important pollination agents for a number of plants (Weems 2000).
Adults of this species are also fond of eating the sugary honeydew secreted by aphids. They often visit aphids in order to lay their eggs in proximity to them (Weems 2000). When their eggs hatch, the young larvae eat the aphids themselves. Since aphids are often destructive pests of crops, this species and several others have potential as biological control agents (Bugg 2008).
Bugg, R.L. 2008. Flower Flies (Syrphidae) and Other Biological Control Agents for Aphids in Vegetable Crops. Publication 8285. University of California Division of Agriculture and National Resources.
Weems, H.V. 2000. A Hover Fly, Allograpta obliqua (Say) (Insecta: Diptera: Syrphidae). DPI Entomology Circular 106. Entomology and Nematology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida.