Spathius galinae wasps will be used to fight emerald ash borer infestations. U.S. Department of Agriculture (USDA) Agricultural Research Service (ARS)/Flickr Wasps don't exactly win popularity contests, so why is the federal government releasing millions of them in 24 states — on purpose?

First of all, these aren't what you think of when you think of wasps. They're tiny, they aren't yellow, and they don't sting humans.

These wasps are actually on our side: a bug army deployed in a desperate attempt to save our dying trees.

The US Department of Agriculture hopes that these special wasps will be a key ally in the fight against emerald ash borers, invasive beetles whose larvae have destroyed trees across vast swaths of northern and eastern America in just a few decades.

Scientists don't want to douse half the country in pesticides, so they're trying a craftier approach by enlisting the emerald ash borers' natural enemies. This isn't the first time the government has tried this clever strategy, but the effort has never reached across so many states at once.

The USDA found four types of wasps to try against the emerald ash borers. They all lay their eggs inside borer eggs or larvae, killing them before they turn into wood-munching beetles. Government scientists spent some time figuring out how to make these wasps happy before their deployment and made sure that the wasps wouldn't go after anything besides emerald ash borers.

Once released, the wasps will track down emerald ash borers by sniffing at ash trees — they can actually smell the difference between healthy trees and infected ones. Each wasp will zero in on a target by feeling out the vibrations the beetle larva causes as it roots through the tree. Then, the wasp lays its eggs on the baby emerald ash borer. When the wasp eggs hatch, the baby wasps will feed off the emerald ash borer, killing it.

While the wasps can't save trees that are already damaged, they can — scientists hope — reduce emerald ash borer populations enough to protect trees that are healthy.

An emerald ash borer larva. Mike Groll/AP

Why make such a fuss about some bugs? It turns out that the 8 billion commercial timber trees those pesky beetles want to destroy are worth about $280 billion, all told. Replacing all of the ash trees we've planted in cities and towns would be another $25 billion.

The wasps won't be fighting emerald ash borers alone, though. Woodpeckers, which enjoy a nice snack of borer larvae, are another key ally.