September is more than the return of school days and fall colors in Michigan — it’s also the peak of yellowjacket season.

And this year, they are especially aggressive and likely to sting. Entomologists tell Bridge Michigan that yellowjackets develop a sweet tooth in August, making them more likely to sting.

To defend yourself, sprays are most effective in the morning or evening. Your best bet is to leave them alone and give them space. Swatting at them will just agitate them, and stepping on one releases an odor that attracts more yellowjackets.

Most of them nest underground, but colonies of as many as 5,000 of them can be found in trees, shrubs, wood piles, and houses.