It’s an unremarkable door, really. Gray in color and built into the hillside beneath the greenhouses behind Birge Hall, it does not draw attention from passersby walking to and from classes. But in approaching the door, an odor is present — not an aroma, mind you, but an unpleasant reek.

The smell comes from the bodies. These animal carcasses are located in a hidden subterranean chamber known simply today as “The Bug Room.”

“They offered me a key to it,” said Jim, a maintenance worker whose daily rounds take him to the Birge Hall complex, “but I didn’t want one. I’ve been in there, but it’s not my favorite place to go. The smell can get to you.”

The mysterious door to The Bug Room conceals a remnant of an earlier time, a dungeon-like space with a gruesome contemporary function and a strange past.

In 1876, the federal government approached the university regents to request the construction of a magnetic observatory on campus. Professor John E. Davies, the University of Wisconsin’s Instructor of Agronomy and Physics, was to oversee the observatory.

The venture’s scientific purpose was to yield, “a continuous and reliable record of the variations in the direction and intensity of the earth’s magnetic force, by means of photographic self-registration.”

The proposal was soon acted upon.

UW president Bascom noted, “The interests of science, as well as state pride, dictated a prompt acceptance of the proposal.”

The next year saw the construction of the university’s first structure for a federal scientific-research project. Constructed underground by local mason James Livesey (who also built North Hall), the 16- by 18-foot vault with an arched brick ceiling was built for $1,200 from plans designed by architect D.R. Jones (who also designed campus’ Washburn Observatory).

Built entirely of masonry and waterproofed with hydraulic cement, the observatory was six feet below grade and surrounded by an outer wall that created a three-foot “dead air” space, or chamber within a chamber, intended to provide for a steady temperature. Only a handful of ventilator shafts above ground denoted the presence of the observatory. Similar observatories were built in Paris, Toronto and Greenwich, England.

Federal equipment filled the chamber in its early years. A self-recording magnetograph and a magnetic declinometer, instruments used to track the motion of a very precise and isolated pendulum, were used to generate data which was used by the Coast and Geodetic Survey Department to study sunspot activity and aurora effects, as well as in efforts to predict the weather.

Experiments went on for only 10 years, however, until in 1888, the U.S. Congress eliminated the Coast and Geodetic Survey Department after extensive corruption was discovered. The instruments were removed to Point Barrow, Ala., and the observatory became, according to the school newspaper at the time, “a campus curiosity.”

The old magnetic observatory, or “Old Met Lab,” did not sit idle forever, though. Dr. Harry Russell used the stable temperature of the structure for experiments in the curing of cheese in 1896. Later inventories listed the observatory as an oil-storage house and potato cellar. According to the book Buildings of the University of Wisconsin, the physical plant refers to the observatory as “The Root Cellar.”

The facility also holds a special place in the history of the professional chemistry fraternity, Alpha Chi Sigma. It was there in April of 1903 that the fraternity’s first new members were initiated. According to the UW Zoological Museum’s website, “The cool, secretive, and echo-ey atmosphere of the lab gave rise to fraternity lore that persists to the present day.”

Today, the fraternity no longer conducts ceremonies in the structure, however. After Birge Hall was constructed a short distance away in 1912, greenhouses were added right over the top of the chamber.

But back to the odor behind the door.

The year 1950 saw the renovation of the old observatory for utilization by the Department of Zoology at a cost of $4,134. Modern heat and a new door were added later. So were the bugs.

The University’s Zoological Museum currently uses the chamber for its “Dermestid Colony,” a collection of large stainless steel tanks that house masses of dermestid beetles. Museum staff members place skinned animal specimen carcasses in the tanks where the beetle larvae feed voraciously on the dead animal flesh for a few days or weeks until the skeleton is left remarkably clean. According to the museum’s website, “Only minor preparation is needed before the specimen can be cataloged into the museum’s research collections.”

Paula Holahan, the museum’s curator of mammals and birds, described the process.

“The bodies are put in boxes to keep the bones from getting mixed up. Paper toweling is put over the carcasses to simulate skin, which the beetles crawl under,” she said. “Each tank’s population varies. It can be in the thousands at times.”

The museum’s website also speaks of the need for “constant vigilance” to maintain proper temperature, humidity, cleanliness and food-availability for the beetles. Smell, however, is obviously not a major concern for the dermestids.

Students seeking a whiff of the enigmatic vault’s air will be disappointed too: The Bug Room is not open for public tours or use.

“We don’t do public tours due to the nature of the specimens in there,” said Holahan.