We want to introduce you to a predatory insect that you will find in your cropping systems, and it’s a fly! Predatory gall midges belong to the Cecidomyiidae family and undergo complete metamorphosis from egg through three larval instars, pupa, and finally, the adult stage (Figure 1). This insect overwinters as larvae in cocoons in the soil and pupates during spring. While all life stages of this insect may not be easy to identify, they are beneficial to have around.
Figure 1. Predatory gall midge life cycle (design by Sheyla Zablah).
The larvae are carnivorous, feeding on aphids, making them predators in agricultural fields and high tunnels. In the recent Insect Spotlight on Syrphid Flies (Issue 737), we noted that the larvae of predatory gall midges are occasionally mistaken for syrphid larvae. While both of these organisms are true flies belonging to the order Diptera, there are significant differences in the appearance of adults and larvae. Adults are characterized by long, hairy legs and distinct wing venation (Figure 2), which are very different from the bee mimics that adult syrphid flies resemble. Similar to syrphids, adult midge flies feed on pollen and live for a short period of time. The larval stage may be confused with syrphid flies. However, predatory gall midge larvae are more brightly colored (yellow, orange, and red) and have less distinct segmentation between body parts (Figure 3). Species such as Aphidoletes aphidimyza are natural enemies that effectively suppress pest aphid populations, typically emerging in late spring and summer. During recent farm visits, our lab has observed a significant population of these midges inside high tunnels infested with aphids.
Figure 2. Adult predatory gall midge (Photo by John Obermeyer).
Figure 3. Predatory gall midge larva (Photo by John Obermeyer).
Aphidoletes aphidimyza larvae are also commercially available through various beneficial insect suppliers such as Biobest, Biobee, Arbico, and Koppert. Additionally, they can naturally establish themselves in aphid-infested crops.
Predatory gall midges, Aphidoletes aphidimyza, are important predators in IPM, offering biological control of aphid populations in agricultural settings! Keep an eye out for this beneficial insect.