Syrphid flies are a wonderful, dedicated members of your Garden Patrol. They are hardworking and report for duty starting very early in spring. So you want to be sure to have early blooming flowers and weeds, trees, and shrubs around your garden.
I'm having aphid problems on my tomato and pepper seedlings that were started inside because the spring thaw brought invading ants who brought their aphids to pasture on my seedlings. My indoor Garden Patrol of ladybugs and occasional aphid mummy maker wasps have been keeping them under control but not entirely, and I have been occasionally helping by picking them off with moistened bamboo skewer.
Now that the weather has been warm enough to harden the tomato seedlings off, they have been spending occasional overnights outside... And yesterday morning, when I was tsk, tsking over the aphids, I noticed a hoverfly making stops and reaching with the tip of her abdomen in the classic ovipositing motion. Later, as I was closely inspecting the seedlings, I noticed these
https://zebrachipscri.tamu.edu/image-gal ... predators/
Here's one more link : https://mint.ippc.orst.edu/syrphid.htm