Crazy, snaky worms in your garden? Could be jumping worms, Amynthas spp.

 

Vigorous snake-like movements and a saddle-like pale white band called the clitellum encircling the body are diagnostic clues to the identity of jumping worms. Credit: Paula M. Shrewsbury, PhD

 

Last week we met hammerhead worms as they slithered around a landscape preying on hapless earthworms and mildly terrorizing homeowners and their pets. This week we once again depart from our usual six-legged theme to meet another invader from Asia which is now a pariah in our gardens and natural landscapes. Despite not having legs, these snaky wigglers go by the name of jumping worms. Jumping worms are not close kin to hammerhead worms, which belong to the clan of repulsive creatures including liver flukes and tapeworms. Jumping worms are annelids, relatives of more familiar non-native earthworms like nightcrawlers, those large soil dwellers we gathered after a rainstorm to use for fish bait. One of the most common species of earthworm is the European nightcrawler, Lumbricus terrestris. Its deep vertical burrows help aerate soil, facilitating gas exchange for the roots of plants. Its burrowing behavior helps to reduce soil compaction and allows water to infiltrate soil, thereby giving plants critical raw material for photosynthesis. Waste products excreted by earthworms, called castings, are rich in nutrients vital to plants and act as a natural fertilizer, improving soil structure and fertility. 

If worms in your garden behave more like snakes than slowly moving nightcrawlers, it’s a good bet that they are jumping worms. Wrangling them for fish bait can be challenging. Watch as one begins to drop its tail, a clever trick called autotomy which may help it escape from predators.

But not all worms create deep burrows in soil. Nor do they feed on soil and organic material underground, facilitating a slow steady release of nutrients to plants. Some worms make their living on the surface of the soil in what is called the epigeic zone. This is the realm of jumping worms, and several species have invaded North America dating back to the 1800s. One species of jumping worm, Amynthas agrestis, has been in Maryland since the 1930’s. Jumping worms also seem to be spreading throughout our nation. A report in 2021 enumerated 15 states with jumping worms. A peek at the current jumping worm map in iNaturalist indicates their presence in more than three dozen states. Jumping worms are highly active and slither with rapid snake-like movements when plucked from the soil. When harassed by humans and presumable predators, they will drop their tail segments in a feat called autotomy. The missing tail can be regenerated by the worm. This may give a would-be predator an appeasement snack while allowing the rest of the worm to escape and live another day.

Jumping worms produce coffee-ground-like excrement called worm castings. These appear on the surface of the soil and are another indicator of a jumping worm infestation. Paula M. Shrewsbury, PhD

What threat do jumping worms pose? Their ability to rapidly breakdown leaf litter at the soil surface and their lack of creating burrows in the soil dramatically alters the composition and subsurface nutrient content of soil. Soil infested with jumping worms tends to be drier with a consistency similar to coffee grounds. This radically changes the diversity and composition of micro and macro-organisms that live in the soil. As a result, well-established associations of microbes, plants, and animals in our forests and managed landscapes are disrupted. Scientists suggest that these perturbations disfavor our native flora and fauna and open the door for invasions of non-native species. Management of these invaders mirrors that of other soil borne invaders, including hammerhead worms. Jumping worms move in soil and soil amendments including mulch, so prevention is the key. When purchasing mulch be sure it has been processed, meaning that it has been heated to a temperature that will kill all life stages of jumping worms. Unprocessed mulch purchased in bags or bulk can be placed in the sun for several days in their bags or covered with plastic sheets if purchased in bulk. Several days of temperatures of 105 Fahrenheit or better will kill the worms and “cocoons” that harbor their eggs. Soil on tools, pails, or footwear may also transport eggs from one location to another, as will movement of plants from infested soils. When you find these snaky devils in your soil, bag them and destroy them by whatever means is your pleasure and dispose of them in the garbage. Don’t trade plants with others if your flower beds are infested. Anglers may also unwittingly move jumping worms if they purchased worms commercially for fishing. Purchasing something with a name like Alabama Jumper or Georgia Jumper is asking for trouble. Even if you buy good old nightcrawlers, when you are done fishing and left with a Styrofoam cup of dirt, please don’t leave it on the riverbank. It may contain eggs of jumping worms. Put it in a sealed plastic bag if you can and dispose of it in a garbage can.

To learn more about jumping worms, please click on this link:  https://extension.umd.edu/resource/invasive-jumping-worms

Acknowledgements

We thank Deak and Sheri for sharing their jumping worms which served as the inspiration for this episode. Dr. Shrewsbury was the worm wrangler and provided lovely images of worms. Our thanks to her. “Invasive Jumping Worms That Violently Thrash If Handled Now in at Least 15 U.S. States” by  Jason Murdock, “ Invasive Jumping Worms” by Christa Carignan, and “Jumping/Crazy/Snake Worms – Amynthas spp.” by  Tawny Simisky and Dr. Olga Kostromytska where consulted to prepare this episode.

Hammer time in the DMV: Hammerhead worms, Bipalium spp.

 

One look at a hammerhead worm lets you know how it got its name. Image credit: Kevin Ambrose

 

Ok, I know, this is supposed to be Bug of the Week, not Worm of the Week, but sometimes something so weird and creepy pops up that we need to spend some time on it. Last week a friend called and inquired if I had ever heard of hammerhead worms. I have heard of hammerhead sharks, hammerhead flies, and, of course M C Hammer from back in the day, but hammerhead worms, not so much. Turns out that a residence in northern Virginia is beset with creepy, slithering, predatory flatworms which make early morning forays to hunt and dine on unsuspecting earthworms, molluscs, and other small invertebrates in the landscape, as well as each other. These rascals from Asia are largely unseen in the lawn but clearly visible as they glide in slow motion across a driveway on a cool dewy morning.

In the damp warmth of a summer morning, hammerhead worms can be found on paved surfaces as they move about the landscape. Image credit: Kevin Ambrose

Attempts to capture and remove the worms results in spontaneous fracturing of their bodies. Is this the demise of these creepy invaders? Not at all. Here’s why not. My first encounter with the clan of flatworms, the Platyhelminthes, was in high school biology where we met cute cross-eyed planaria. We were encouraged to cut these creatures in half so we could observe the mysterious and baffling phenomenon of body part regeneration. That’s right, slice these little guys in half and they fully regenerate the complementary portions of each body part, a miraculous two from one deal. Well, as members of the flatworm clan, it turns out that hammerhead worms can also regenerate missing body parts. My friend reported the individual segments of his fractured hammerhead worms independently slithered off the driveway into the grass where we can assume that they regenerated missing parts and resumed their hunt for small invertebrates. Hammerhead worms lack true mouthparts and they don’t chomp prey with jaws as do beetles or wasps. These flatworms immobilize victims with a coating of sticky slime, evert part of their digestive tract, and plunge it into the prey, where they slurp up body fluids and small particles of tissue.

In a small Tupperware bowl filled with soil and earthworms, hammerhead worms reveal how they got their name and how they roll. Their genus, Bipalium, is Latin for two-shovel and their expanded head does indeed resemble a two-sided shovel or spade. Watch as one cruises the container, investigating soil with its expanded head. Awhile later, I found it caressing the carcass of an earthworm. Potent tetrodotoxin secreted by the worm may help it subdue prey. Soon thereafter the worm investigated the deflated remains of one of its kin. Hammerhead worms are cannibalistic. Worms courtesy of Kevin Ambrose.

While this was my first encounter with hammerhead worms, they have been here in the US since 1901. They are commonly found in greenhouses in more than 14 states. Beyond greenhouses, iNaturalist reports thousands of sightings of hammerhead worms throughout the US, including several here in the DMV. So be on the lookout for these slimy rascals and if you spot one, please add your sighting to iNaturalist and maybe report your find to the state Department of Agriculture.  

At 22 inches in length, this hammerhead worm takes first prize in the “how big can they get?” competition. Image credit: Kevin Ambrose

Oh, there is one last bit of creepy business associated with hammerhead worms. I had to wonder how this kind of slow-moving creature could assail and capture prey including more massive earthworms or slugs. In addition to super sticky slime, hammerhead worms have one more trick to subdue prey. They secrete potent, paralyzing tetrodotoxin, the same lethal toxin found in puffer fish. Tetrodotoxin is believed to incapacitate large prey so they can be consumed by the worm. This nasty toxin may also help the worm defend itself from its own predators. Domestic animals that contact or consume these worms may experience discomfort or illness and people who have handled the worm report skin irritations. So, heed the warning delivered by the Hammer back in the 90’s when he said “you can’t touch this.”    

To learn more about hammerhead worms in the DMV, please click on this link:  https://www.washingtonpost.com/weather/2023/07/22/hammerhead-worms-invasive-poisonous-dc/

Acknowledgements

Bug of the Week thanks Kevin Ambrose for sharing images and specimens of hammerhead worms that served as the inspiration for this episode. Articles used to prepare this story include the following: “Land Planarians, Bipalium kewense Moseley and Dolichoplana striata Moseley (Tricladida: Terricola)” by P. M. Choate and R. A. Dunn, “Confirmation and Distribution of Tetrodotoxin for the First Time in Terrestrial Invertebrates: Two Terrestrial Flatworm Species (Bipalium adventitium and Bipalium kewense) by Amber N. Stokes, Peter K. Ducey, Lorin Neuman-Lee, Charles T. Hanifin, Susannah S. French, Michael E. Pfrender, Edmund D. Brodie III, Edmund D. Brodie Jr., and “Hammerhead flatworm/Hammerhead slug” by the Texas Invasive Species Institute. We also thank Joan Hahn for introducing students to the wonders of flatworms and biology at Randolph High School.

My what ginormous jaws you have my dear: Elephant stag beetle Lucanus elaphus

 

With jaws almost as long as its body, the elephant stag beetle is the largest of its kind in the United States.

 

Other stag beetles with somewhat less impressive mandibles like this reddish-brown stag beetle also help recycle wood here in the DMV and around the nation.

Last July we met the pleasant reddish-brown stag beetle and learned about the male’s prodigious horns, battle gear used for combat with other male stag beetles to secure access to females and their breeding sites in decaying stumps and rotting wood. This week we meet the giant stag beetle discovered by an avid insect and nature lover in coastal Virginia. The rack on the male giant stag beetle simply dwarfs mandibular ornamentation of other stag beetles here in the DMV and throughout the United States. Stag beetles are relatives of rhinoceros beetles we met in a previous episode. Male rhinoceros beetles, like our indigenous Hercules beetle, also use prodigious horns on their head to battle competitors for access to females. Amazingly large horns on rhinoceros beetles and ridiculously giant jaws of stag beetles may confer a selective advantage in winning the favors of comely female beetles, hence the continued selective pressure for large weaponry.

Stag beetles dwell in damp forest woodlands where females seek moist decaying stumps or decomposing logs, often in low-lying undisturbed forests. Wet decaying wood serves as the favored location for female beetles to deposit eggs. Larvae, aka grubs, hatch from these eggs and develop over a period of one to two years as they consume lignified tissues of their woody hosts. Stag beetle larvae house a rich microbial community in their gut. These symbionts release nutrients locked in tough woody tissues, making these goodies available to support the growth and development of stag beetle grubs. Along with several other species of wood digesting insects, lucanid larvae play a critical role in recycling organic matter in forests around the world. Adult lucanid beetles are reported to dine on fermenting exudates of plants and sweet honeydew excreted by sap-sucking insects. As you will see in the video, they are also very fond of fruit. As a house guest and star of this episode, our elephant stag beetle demonstrated a particular preference for cherries over grapes and bananas. Lucky for us and him that cherries are in season. The important role of these forest recyclers is imperiled as natural forested lands disappear and become housing developments, business parks, or heavily managed landscapes. A close relative of our elephant stag beetle, the charismatic Lucanus cervus, has declined dramatically in some parts of Europe.  

Check out the jaws on a male reddish-brown stag beetle. Now look at the jaws on the largest stag beetle in the US, the elephant stag beetle. Wow! Watch as this handsome male explores the trunk of a maple tree. The ginormous mandibles are battle-gear used to combat other males for mating rights to female stag beetles. Before returning this one to the wild, I invited this guy in for a fruity snack. Watch as his tiny mouthparts beneath his jaws lap up juicy liquids. With grapes, bananas, and cherries on the menu, cherries turned out to be the winner. Good choice.

Armament such as gnarly teeth and forks help male stag beetles grapple with other males.

Stag beetles are noisy, somewhat clumsy fliers and they create quite a buzz as they zoom though the forest or zero in on your porch light at nighttime. If you are a bug geek like me, you might just want to hold one of these large stag beetles. Worried about those jaws? Well, my house guest did test his jaws on my index finger and although this resulted in a brief adrenaline rush, his jaws failed to break my skin or inflict any pain. Not recommending that you try this, just saying. Stag beetles have very sticky claws at the tips of their feet which enable them to climb trees and grip tightly to nosy humans. According to the Maryland Biodiversity Project, July is an excellent month to spot these fascinating creatures here in the DMV. Head for the forest to catch a glimpse of these giants of the beetle world.

Watch this amazing National Geographic video to see how stag beetles use their supersized jaws to defeat competitors and gain access to mates: https://www.youtube.com/watch?v=-VWFreC4onI

Acknowledgements

Bug of the Week thanks insect lover Jackie for sharing her handsome stag beetle with us. We consulted these references for this episode: “Stag beetles” by Eric P. Benson, “Divergence in Gut Bacterial Community Structure between Male and Female Stag Beetles Odontolabis fallaciosa (Coleoptera, Lucanidae)” by  Xia Wan, Yu Jiang, Yuyan Cao, Binghua Sun and Xingjia Xiang, “Insights into the ecology, genetics and distribution of Lucanus elaphus Fabricius (Coleoptera: Lucanidae), North America's giant stag beetle” by Michael Ulyshen, Louis  Zachos, John Stireman, Thomas Sheehan, and Ryan Garrick, and “Distribution of Lucanus elaphus Linnaeus (Coleoptera: Lucanidae) in North America” by C. L. Staines.