The Crazy Snake Worm (Amynthas agrestis, Figure A1) is an aggressively invasive earthworm that hails from Korea and Japan. Most earthworm species found in Vermont have probably come into North America by early colonial trading with Europe. These worms are in the family of Lumbricidae. The new invaders are from East Asia and are in the earthworm family Megascolecidae. There are several Amynthas species in the North East. These species are usually called Jumper worms (Alabama Jumpers), Wrigglers (Jersey Wrigglers) or Snake Worms. It is difficult to differentiate among these species by looking at their external appearance. One needs to look at the internal organs of these worms to tell which species they are. The only Amynthas species found in Vermont to this date are Amynthas agrestis.
These worms are very aggressive invaders that change forest structure and the
decomposer community in the affected forests. This may have long range effects on these forests (Figure A2) including a reduction in forest regeneration. Just imagine a world without maple syrup … Because of the devastating effect on the forest floor vegetation, some other organisms such as ground nesting birds are affected as their nests are no longer hidden from nest predators. Our lab is trying to find where these earthworms are in Vermont although we frequently stumble upon them by chance. The range of this earthworm in Vermont as we know is shown in Figure A3. We ask for your help to find as many places that have been invaded as possible: if you have seen them at your house or a forest near you let us know
by adding a blog comment which should include an address or the coordinates of where you have seen them. At your home look at mulched flower beds, compost piles, and adjacent woods. Other places where you might find them are nurseries and mulched beds in your local park, community garden and parking lot. I found them in the oddest places. For example, they were happily snaking around in mulched beds of a parking lot in Colchester and the ornamental beds of the Williston I89S rest stop. And yes, I have them at my house too and curse them every time I buy more mulch for my ornamental beds. They love mulch and go through it as though there was not tomorrow. Eventually you get wise and stop feeding them that mulch. Yes, they can decompose woody mulch. They stimulate the production of lignin decomposing enzymes (Figure A4). You even see them in decomposing logs.
Here is when to look for them: The best time to find them is from end of June to mid-October (Figure A5). That is when they are most abundant. They hatch in April around these parts when temperatures have risen above 50 F for the first time but you won’t be able to see their tell-tale saddle or clitellum that stretches all the way around the circumference of their body (Figure A1) until they are adults. You can tell them even when they are still juveniles and don’t have that saddle. They tend to squirm a lot, move like snakes and sometimes lose their tails in an attempt to get away from you.
April 7 and 8, 2014: Last week we collected temperature data at the horticultural Research Center (University of Vermont) in South Burlington. Soil temperatures stayed at or below 0 C from January 25 to April 1, 2014 (blue line, Figure A6) even though there were large swings in ambient temperature (red line). This was probably due to snow cover. Unlike in other years, the soil was frozen. Ice reached to a depth of approximately 4 cm.
April 8, 2014. We went to an Amynthas-invaded forest site in Huntington where, to our surprise, we found a lot of potential hatchlings which are now being incubated in the lab at 15 C. We found them in the leaf litter both under snow and patches where the snow had already melted. Soils were still frozen and temperatures in the leaf litter were 4 C and under the snow 1 C. Ambient temperatures at 2:30 pm were 9 C. The suspected hatchlings were in water films on and between leaves. Pictures below shows Korkmaz Belliturk and Josef Gorres at Huntington today (picture credit: Naomi Cunningham).
February 12, 2014. We counted the hatchlings from Huntington. We found 111 potential hatchlings on leaves collected from 6 quadrats that were 20 by 20 cm in size. That translates into approximately 400 hatchlings per square meter or 40 per square foot. Since collection of these hatchlings they have been growing in the cool temperature incubator. On February 10 we surveyed the invasion site at the Horticultural Research Center at UVM. We only found 1 potential hatchling in 5 plots of 30 cm X 30 cm area. This site was dryer than Huntington.
May 19, 2018. Here are some readings on the ecology of pheretimoid earthworms which includes Amynthas: Selected Amynthas Resources MISN
We are now back in the field season, collecting cocoons and hatchlings from the woodlands. As usual there is another bumper year of Amynthas earthworms expected in the woodlands we are surveying.
Here is a map of confirmed Amynthas sightings in the Northeast. Your Amynthas populations is likely not on it since only scientist confirmed sites are shown.
As you can see pheretimoids are quite widely spread in the region. Confirmed pheretimoid locations are shown as a circle on the map. You notice clusters of confirmed locations on the map. This indicates that there is a research group working on these earthworms in that area. Active groups are at the University of Wisconsin, University of Minnesota, Cornell University, Colgate University, Johns Hopkins University, University of Massachusetts, and of course here at the University of Vermont.
When looking at populations of earthworms we are frequently just looking at the worms that we can see. There also is a more cryptic side of the population: cocoons. Cocoons are small, between 2 and 4 mm in size and difficult to see in the soil. You have to extract them laboriously (hmph!). But after you extract the scientific loot is great, you learn that there may be a couple of thousand cocoons per square meter, and that at any time of the year part of that cryptic cocoon population is ready to hatch. In an experiment started in June 2016 we buried in our woodland soils cocoons (contained laundry type bags) produced in 2015 and inspected them every month. We removed any hatchlings so there would be no additional cocoon production. Well, the outcome of it was that in July 2017 about 20% of the buried cocoons were still viable. — Bad — The cocoons may last through several winters which would make controlling these earthworms even harder. We have to repeat this experiment to make sure that our conclusions from that first experiment are valid. If they are then we are dealing with a cocoon bank that acts like a seed bank.
On cocoons, check out this paper: 2017 Biological Invasions (in press).
It says that these worms hatch in the winter when temperatures are high (e.g. January thaw).
Here is a picture of a cocoon. the picture was taken by Maryam Nouri-Aiin, my current graduate student.