Tiny Black Bugs - Fruit Flies or Fungus Gnats?

In lieu of a dog or cat, we have various insects living at our house. Most prominent lately have been these tiny black flying things. But they're too small and too active to really get a decent picture. But this week I found one floating in a little water at the bottom of a cup on the table. These guys sometimes seem to come home with bananas and they like any kitchen scraps we haven't covered well before taking them out to the compost. And we're at the season change time when our backyard compost takes its winter break and we haven't quite gotten used to the garbage disposal yet.

But with a picture in hand, I finally called Cooperative Extension to see if I could identify the little critters. Because they liked the fruit he thought they might be fruit flies, but when he saw the picture he called to say they were Fungus Gnats.

He sent me a link to the Colorado State  Extension site where I learned:

Fungus gnats (Bradysia species) – also known as dark-winged fungus gnats, are small, mosquito-like insects often found in homes and offices, usually in the vicinity of houseplants. They are considered a nuisance when present in noticeable numbers, but the adults are harmless insects that do not bite. Fungus gnat larvae develop in the growing medium of houseplants and are considered minor pests of houseplants. . .

They are really small, I took another picture with a grain of uncooked rice floating next to it.

The most important strategy to minimize fungus gnat problems associated with houseplants is to allow the growing medium to dry between watering, especially the top 1 to 2 inches. The dry-growing medium will decrease survival of any eggs laid and/or larvae that hatch from the eggs as well as reduce the attractiveness of the growing medium to egg-laying adult females. In addition, it is recommended to re-pot every so often, particularly when the growing medium has “broken down” and is retaining too much moisture. Furthermore, be sure to remove any containers with an abundance of decaying plant matter such as decayed bulbs and roots, which provide an excellent food source for fungus gnat larvae. . .

 Want to see if there are larvae growing in your potted plant soil?  But do you really want to find these guys?  (The larvae picture - on a potato - is from the Colorado State site.)

"An effective means of detecting the presence of fungus gnat larvae is to insert 1/4 inch slices or wedges of potato into the growing medium. Larvae will migrate to the potato and start feeding within a few days. The potato slices should be turned over to look for larvae present on the underside."

And the fruit fly?  That looks totally different.  Picture and text are from an Oklahoma State webpage

Life Cycle: Female fruit flies lay their eggs on the surface of rotting fruits and vegetables. Each female may lay as many as 500 eggs. These eggs hatch into larvae which molt twice before becoming fully grown. The larvae feed on the yeast organisms and fungi growing in infested material, and through their feeding efforts, they soon turn their food into a semi-liquid "mess." When the full-grown larvae are ready to pupate, they leave the food material for dryer areas. Complete development from egg to adult under summer conditions may be completed in 8 to 10 days. Mating takes place soon after adult emergence, usually within a few hours, and egg laying begins about 24 hours later.

There's a lot more on the links if you want to know more.