A queen bumblebee can birth males—called drones—on her own. But only after a male fertilizes her eggs can she produce female bees. This is crucial, because drones are essentially layabouts. It’s the women, the worker bees, that do all the foraging to sustain a colony. So inside a mating cage, Strange places a queen bumblebee, and on the other side a drone infected with Nosema bombi. Already this fungus has spreads down the bee’s throat, has rooted itself in the gut where the spores “proliferate like crazy,” according to Strange.

There the fungus swells in the soft tissue between the bumblebee’s organs until the drone grows so plump it can’t bend its abdomen to mate with the queen. Without fertilization, the queen can only birth more males. Without females, future colonies starve.

It’s devastating for bees, and perplexing for scientists, because the oddest part of Nosema bombi is that it’s lived alongside bumblebees for centuries.

“We still don’t know why this fungus went from being not so bad, to really bad for certain bees,” Strange told me.

Answering that question might determine if the rusty-patched bumblebee survives. And because this is the first bee in the continental U.S. to get federal protection, whatever plan entomologist come up with will undoubtedly shape how conservationists protect other pollinators, even honeybees, which have been ravaged by similarly mysterious die-offs. In the case of the honeybees, it’s estimated that the U.S. lost 44 percent of the population last year, caused by the not-yet-fully understood colony collapse disorder. There are several theories about why the bees leave seemingly healthy hives and never return, and some of these theories include the spread of disease or parasites, similar to what may have devastated the rusty-patched bumblebee. So many entomologists and conservationists see protecting the rusty-patched bumblebee not as a fight for one species, but the beginning of a much larger battle to rescue all pollinators. Drawing a protection plan like this has never been tried before, and it presents several novel problems. Right now, the most perplexing is why—if Nosema bombi is to blame for the decline of the rusty-patched bumblebee and its close relatives—did it suddenly became so lethal?

Collectively bees pollinate about 30 percent of the world’s food. Much of that is done by honeybees, which is why most of the news and panic about the massive bee losses has focused on European honeybees that are not indigenous to the U.S.

Bumblebees do not make honey. The some 50 American species mostly pollinate wildflowers, as does the rusty-patched bumblebee. It gets its name from a rust-colored square on its back, which is distinct to the species, but it generally shares common bumblebee traits: They’re more plump than honeybees, their bodies often covered in a thick fuzz, and they’re one of the few insects able to regulate body temperature. All of this allows them to live in higher altitude alpine environments, which makes them critical to the plants and animals that live there. Bumblebees are also distinct in that each year nearly their entire colony, comprised of hundreds of bumblebees, dies.

(The Xerces Society)

In the early spring a queen emerges from her hibernation hole dug beneath a few centimeters of soft soil and searches for an unused rodent den, a dead tree, even a heap of grass clippings to begin her colony. To build it she gathers pollen and creates waxen pots laden with eggs. The first born are previously fertilized worker bees that find food and build up the colony until survival efforts turn to needs for expansion sometime in the late summer. Now the queen lays the colony’s reproductive members: more queens and the male drone bumblebees. The males will leave the colony in search of other queens, never to return, and when winter comes again every bumblebee but the queens die.