It's almost spring. Once again, my plants are prey to slugs. Damp overcast yet warmer days provide the ideal environment for these slimy shell-less mollusks. Their stealth but obvious presence is unmistakable. Hiding by day, foraging by night slugs slide across the smooth leaves of succulents, chewing erratic holes. Up and over the daffodils they glide, nipping off tender petal tips and leaving behind their tell-tale silvery mucous trail. Most gardeners agree that slugs have little chance of redeeming their repulsive reputation.

 

But during World War I, this common but destructive garden pest saved countless American soldiers who themselves were falling prey to mustard gas. In 1917, when the Germans first used this deadly chemical weapon, troops had difficulty detecting it when entering a contaminated area or during a direct attack. The gas lingered in the trenches for days, especially during cold temperatures.

 

Hydrochloric acid is produced when mustard gas comes in contact with moisture. Lung membranes are damaged. Severe respiratory complications follow. Thousands of soldiers were either incapacitated or died from exposure, along with horses and dogs — the military working animals also stationed on the Western Front.

 

Then along came the slug — thanks to Dr. Paul Bartsch, a curator in the Division of Mollusks at the U.S. National Museum (currently the National Museum of Natural History). Curious why slugs (Limax maximus) in the furnace room of his home were sensitive to the fumes, he studied and tested their olfactory capabilities, discovering their extraordinary ability to protect the lung membrane by closing the breathing aperture. He also learned that their tentacles were so sensitive to smell they could detect the scent of fungi in gardens and in the woods.

 

According to the Smithsonian Institution Archives, Dr. Bartsch's slugs were three times more sensitive than humans to mustard gas, reacting at levels of one particle per 10-12 million by compressing their bodies and closing off their breathing pores, then surviving the gas attacks without a problem — unlike the often fatal response of humans, horses and dogs.

 

As a result, the U. S. Army in June of 1918, enlisted ordinary garden slugs to fight in the trenches. They were carried in by the troops. During their five-month tour of duty, these gas-detecting heroes saved thousands of lives by alerting soldiers to the presence of mustard gas. By observing the slugs' compressed bodies, soldiers could put on gas masks before they had any hint of this dangerous chemical weapon.

 

For further information on slugs, check out the following:

 

“Serpents, Slugs and Science: The Interesting Career of Paul Bartsch” at: 
https://siarchives.si.edu/blog/serpents-slugs-and-science-interesting-career-paul-bartsch

“Snails and Slugs,” Pest Notes, Publication 7427, at http://ipm.ucanr.edu/PDF/PESTNOTES/pnsnailsslugs.pdf