Photos by Patty Gillespie.

August 1, 2023

A Burning Question About Bees

Researcher Brenna Decker and landowner Jim Gillespie discuss bees in a prairie. The grasses are taller than the people. And it is a sunny, summer day.
Researcher Brenna Decker and landowner Jim Gillespie discuss bees in a prairie. Photo by Patty Gillespie.

“The thing to do when a sweat bee lands on you is to lightly touch its back,” spoke the gray-haired man with a mischievous smile. The young woman, upon whose arm the bee had landed, knew he was just pulling her leg. She raised her arm to near her face and with a puff of air shoved the bee off. The landowner, Jim Gillespie, and the researcher from the University of Illinois entomology department, Brenna Decker, had met at a restored prairie because both wanted to know how native bee populations respond to land management strategies that include prescribed burns of varied timing.


Decker’s research necessitated that the study’s sites met certain criteria. 1) Land units must measure about three hectares each, must lie adjacent to one another and must exhibit similar topography and vegetative composition. 2) Each unit must represent a restored prairie maintained by a management plan which includes a prescribed fire schedule. 3) That schedule must reflect the implementation of growing-season burns and dormant-season burns. Certain units were required to have been affected by prescribed fire conducted in late summer. Other units were to have been burned during February or March.

In April when Decker had been examining one of the potential study units, a prairie where a dormant-season burn had been conducted in February, she observed that plants were sprouting from bare ground amongst charred plant residue. While noticing young spiderwort plants, she envisioned future blooms of bright blue providing nectar for a bumblebee queen, newly emerged from its underground burrow where it had survived the winter alone.

A rattlesnake master plant being to grow in a field of grass that had been previously burned. It is spring time in the photo so not much vegetation has emerged yet, just a few blades of grass.
Green vegetation appears shortly after a spring dormant season burn. Photo by Patty Gillespie.

Decker saw the linear, serrated leaves of sprouting rattlesnake master and envisioned its globular clusters of little white flowers attracting the attention of small bees starting in late June and continuing through early August. The small bees of Halictus and Lasioglossum would visit those flowers.

Interspersed among short grassy clumps of bluestem were emerging white indigo stems looking like asparagus and showy tick trefoil sprouts looking like baby bean plants. She found partridge pea (another of the Fabaceae family) emerging at this site; its blooms would still be providing fresh pollen and nectar at the end of her sampling season in August.

On that April day while Decker had been investigating another unit, she had had to look more closely to find sprouting wildflowers. Eight months earlier, in August, prescribed fire had traveled through the green prairie vegetation and thatch of that unit. There, grass had grown after the fire and before frost, and so thick short-standing dead stems of grass required her to look closely. She saw young forbs, many of which were the same species as those she had observed in the other unit. Decker thought to herself, “Perfect!”

Proceeding (The Finding of Bees)

Decker’s research would require that she passively and actively sample bees and systematically observe ground cover and floral composition.

Procedure: Starting in early May, then once monthly, at stations situated along 100-meter transects, Decker places colorful bowls containing a detergent-and-water solution at ground level and at one-meter high. For eight hours the soapy water would act to trap bees as they land. For the capture of larger bees, she positions vane traps.

Brenna Decker sets up a bee collection unit with three bright;y colored dishes filled with soapy water.
Brenna Decker sets up a bee collection unit. Photo by Patty Gillespie.

In the morning and again in the afternoon, Decker with a hand-held aerial net searches and collects bees at flowers for one half hour.

Also, Decker establishes random quadrants, where she observes dead plant material, live vegetation, mosses, and bare soil and estimates percentages for the evaluation of potential nesting habitat. By counting inflorescences within the quadrants, Decker determines flower density.

Back at the lab, Decker identifies the collected bees and compiles information about the prairie sites.

And, Bees Abound

In August, out on a prairie during one of Decker’s research days, Gillespie and Decker were pondering the burning question. In consideration of prescribed burning, how does variation in the burn season affect bee populations in prairies?

Making their way through big bluestem grass, they arrived at one of the collecting stations amongst a patch of mountain mint (Pycnanthemum spp.). A spicy fragrance filled the air. Decker said, “During my survey I recorded 15 flowering species in your restored prairies. I discovered that mountain mint is very commonly used as a nectary.”

A bee covered in pollen gathers nectar from a sunflower.
Photo by Patty Gillespie.

While a small brassy bee was making a nuisance of itself, attempting to gather salt from human skin, Decker mentioned that she had found more than 50 different bee species. “So far, the most common has been Lagioglossum versatum – like this little brassy nuisance!”

As Decker and Gillespie conversed, several bees were gathering pollen from the red stamen of the petite yellow blooms of partridge pea (Chamaecrista fasciculata). Decker pointed to one. “Notice its long antennae. Genus: Melissodes. It’s a male. Females of this species have normal antennae, short like most bees.”

“I’ve been seeing a species in the family Andrenidae, ground-nesting bees or mining bees, which seem to avoid areas with too much thatch on the ground, ” Decker noted. “Their habitat must include bare patches of soil. Fire facilitates that.”

Gillespie’s Revelations

Gillespie told Decker that for years his family’s management strategies for their 150 acres of restored prairies had included only prescribed fires in late winter or early spring. “Dormant-season controlled burning was implemented on an every-third-or-fourth-year rotation. And, sowing seed of native species became an after-the-burn springtime ritual.”

A bee with pollen-covered legs rests on a purple coneflower.
A bee gathers nectar on a purple coneflower. Photo by Patty Gillespie.

Gillespie added, “I am concerned about the impact of burns on the animals of the prairie. It seems to me that during late winter, when it is unlikely that a deep snow or a severe cold snap will ensue, the need for wildlife shelter lessens. Ground-nesting birds are not yet laying eggs, and reptiles and amphibians are not yet emerging from hibernation.” He commented that most enigmatic to him was the influence of fire upon insects in consideration of the seasonality of their metamorphic stages.

In 2014 Gillespie researched the advisability of implementing growing-season burns. Studies had indicated that the controlled burns which were being conducted in August (when prairie grasses are green and wildflowers are colorful) were proving to be effective in establishing prairie habitat.

Green in the Mix

Gillespie modified his prairie management plan. “The character of the growing-season burn was a surprise; its efficacy, also! When we entered growing-season burns into our rotation, we began to see improvement in our family’s prairies, even those that were most threatened. Native prairie plants are dominating, strongly competing with invasive herbaceous plants such as Canada goldenrod or sericea lespedeza. Woody encroachment is being stopped. There’s marked reduction in the number of exotic shrubs such as autumn olive.”

Readily discernable is a botanical community’s response to a schedule of prescribed burns, but not so the zoological community’s. Gillespie hoped Decker’s findings would prove to be a window for enlightenment.

Bee Aware

The burning question on Gillespie’s mind was posed to Decker, “So, how do prairie burns of varied timing affect bee population?”

Decker explained that her conclusion was that the timing of a particular burn has little influence upon the bee community. “However, you should be aware that those populations of bees utilizing burned prairies as habitat will be stable only if there is a nearby prairie or forest habitat that has been left unburned for a period, at least for a year,” Decker said.

Apiarian research suggests that there exists a correlation between enhanced diversity in native bee populations and enhanced diversity in native prairie plants brought about by prescribed burning. “Bee numbers grow because burns maintain prairie habitat.”

Gillespie’s response – “That’s what we were hoping to hear!”

For years, Patty Gillespie shared her enthusiasm for language and nature and got paid for it at a public school and at a nature center. Now she plays outdoors as often as she can and writes for the sheer joy of it.

Readings and Conversations Having Influenced the Gillespie Family’s Management Strategies

Vaughn, Allison J. (2014) Prescribed fire in Missouri. Missouri Natural Areas Newsletter 14:1- 3.

Sericea Lespedeza Control

Gardner, Don (2006) Prairie restoration management: art or science, Illinois Steward, University of Illinois Extension 15: 20-24.

Robert Gillespie, Missouri Department of Conservation Southeast Region’s Biologist (2014) Conversations: Scenarios and successes of prescribed burn regimes including growing-season burns conducted by MDC personnel in Missouri, MDC Southeast Regional Office, Cape Girardeau, MO.

Nancy Coutant and Janice Coons. EIU instructors and professors (2008 – 2012) Conversations: Effects of chemicals produced during simulations of prescribed fires on native prairie plants’ seed germination and various prairie management topics. Biology Department, Eastern Illinois University, Charleston, IL.

Students at EIU (2008 -2010) Posters and presentations: Effects of chemicals produced during simulations of prescribed fires on native prairie plants’ seed germination and other prairie management topics. Biology Department, Eastern Illinois University, Charleston, IL.

Brenna Decker (July 14, 2017) Pamphlet and presentation: Bee Walk at Ballard Nature Center. Effects of burn timing on native bee communities within prairies. Entomology Department. University of Illinois Urbana Champaign.

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