Biologist Gerardo Camilo and his team are collecting wild bees in St. Louis, Chicago, and Detroit to better understand why the number and variety of bee species are growing in cities.

In October, Camilo and his research team from Saint Louis University went to a local community garden on a mission. He moved slowly among the tall flowers, okra, and hot peppers as he stalked the bees. Ready with a net gripped tightly in his hand, Camilo trapped his prey then placed each specimen in a jar.

One bee was just slightly larger than a kidney bean and covered in so much pollen that Camilo didn't recognize the species.

"Wow!" he said. "What the hell are you?"

"I think it's a bumblebee," said graduate student Paige Muñiz. "Check out that orange pollen. She looks like a little candy corn."

Camilo says bees are losing habitat in rural areas and that's one reason they are moving to cities. Industrial agriculture has promoted the development of monocultures, a practice where farmers plant one crop over a large area.

That's not particularly welcoming for wild bees—especially the many species that are specialist. The squash bee, for example, prefers the pollen from squash plants. When a farmer who used to grow a variety of crops, such as squash, zucchini, and pumpkins, replaces them with a single crop, such as corn, that change forces bees to find food elsewhere.

"The expansion of monocultures has resulted in very little land left untouched," Camilo says. "The less area we have for native plants, the less habitat and the less resources we have for these beautiful, beautiful organisms."

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Bees collected from urban gardens. (Carolina Hidalgo/St. Louis Public Radio)

Wild bees also nest in the ground, which can make their homes vulnerable to intensive farming practices like tilling.

Ed Spevak, curator of invertebrates at the Saint Louis Zoo, says wild bees are worth saving and an underestimated powerhouse.

"Many of them are actually far better pollinators for a lot of our crops than honeybees are," Spevak said.

In St. Louis, Camilo discovered the largest variety of wild bees in low-income neighborhoods where people may not have the time or money to spend on pest control.

"You have 20 bucks in your pocket," Camilo says. "Are you going to buy pesticide for your sidewalk? No, your preoccupation is putting food on your table than meeting some aesthetic level that's irrelevant to your life."

North St. Louis has lots of vacant lots, full of messy, overgrown weeds.

"People would say it's unkempt because you have all this leftover vegetation," Camilo says. "Well, bees like that because it provides habitat, it provides refuge."

As plant variety declines on farms, potential bee habitats are flourishing in urban spaces. City residents are building community gardens, introducing more flowering plants, and that draws bees.

Recent research suggests that—with a few changes--urban and suburban spaces can be good homes for wild bees. A 2015 study led by conservation scientists in Massachusetts reported that mowing less frequently could attract more pollinators.

Camilo and his colleagues are sharing this information and their findings with St. Louis residents to encourage locals to change their gardening practices.

He also wants to show policymakers that cities can play a critical role in supporting wildlife.

"If we're going to be investing in a sustainable city, what does that look like?" Camilo says. "You know, in terms of food production, in terms of pollinators?

You can't have one without the other, he says.