The World on a Doorstep

Written by:  Joe Staton, PhD

One morning on the way to my intro biology class, I saw on the USCB library steps a large worm crawling around, just after a spring rain.  Not unusual in the Lowcountry, but I recognized it immediately as the large flatworm called the hammerhead worm.  I would say “commonly” called, but this species (Bipalium kewense) is introduced and is only recently common here and other places, from SC to California and as far away as Japan. 

 

Even though it originated in the tropics of Southeast Asia, the species name “kewense” (cu-WIN-see) stems from where the specimen described was originally found, the Royal Botanic (Kew) Gardens near London, England.   This species is the only large, terrestrial, free-living flatworm in North America.

 

Like many other introduced plants and insects, the desire for live exotic foods, plants and pets brings in directly or indirectly species than can “escape” into our local habitats and spread.  The flatworm has moved about with the trade in horticultural plants, and unfortunately, might ultimately be a threat to gardening and agriculture.  As we are crucially aware now of the impact of hive collapse syndrome in bees (Apis mellifera), these hammerhead worms prey on native earthworms, which are the creators of rich organic terrestrial soils that support flower and vegetable gardens, alike. 

 

Most non-biologists do not know that Darwin’s last book was dedicated to describing the importance of the actions of earthworms.   If the “hammerhead” populations increase by too much, they could be a real threat to horticulture hobbyists, nurseries, or even agricultural enterprises and our food supply. 

 

As a humorous aside, I showed the specimen to two of my non-biologist colleagues at USCB.  I exclaimed, “This is the largest free-living flatworm in America!”  They both said, completely seriously, “How do you know?” They then scoffed at me when I said, “Because I’m a zoologist!”  Both had taken me precisely at my word that the very specimen I was holding was possibly a record-breaker for the species.   I’ll do my darnedest not to cause such confusion again.