Ask Us Anything Q&A - AGM 2020

Author

Charlie Bell

Charlie Bell is the Membership Officer for the Earthworm Society of Britain (ESB). For the 2020 virtual AGM she hosted a Q&A session where she invited members to 'Ask Us Anything' (about earthworms) and the ESB sourced answers from our society officers and earthworm experts.

What sort of microscope do you use to look at earthworms?

We use a low-power (sometimes called a ‘dissecting’) stereo microscope.  With the option of just 10x magnification- those starting at 20x can be too much for our larger earthworms. These range in price from around £100 to many thousands of pounds, but a basic model is usually adequate for earthworm identification.  Good lighting is sometimes more important than a good microscope!  For earthworm identification it is helpful to have a light source both below and above your earthworm – these can either be built into the microscope or used separately. The ability to change the angle of the top light is also important, to allow you to better see certain features.  A cheap LED desk lamp is often just as good as a specialist microscope light. More information about microscopes for recording earthworms is available in our Earthworm Recorders Handbook.

For example, the ones we typically use in the courses we run in partnership with the Field Studies Council are this type:

Dissecting microscope diagram
FSC BioLinks project microscope (c) Field Studies Council

Is there a non-fatal / non-harmful way to immobilise earthworms for identification under the microscope? For example, can you pop them in the fridge or freezer?

Currently the only way of reliably identifying earthworms involves looking at them under a microscope and counting which segments various extremely small features occur on.  Live earthworms wriggle from side to side and also expand and contract in length and width, making this extremely difficult to do on a live specimen.  Because of this, earthworms are typically killed and preserved in alcohol before identification can occur.  We have trialled a number of different ways of restraining earthworms, for example trapping them between a thin layer of clingfilm and a Perspex tray and using carbonated water, but in all cases the earthworm continues to move making identification very difficult.  It may also cause distress and discomfort to the earthworm to restrain them in this way.  We also trialled the use of macro photography to capture images of earthworms in order to identify them, but this also proved difficult, and not really viable as a field technique.  A recent trial of both these methods of identifying earthworms proved accurate only about 50% of the time.

We will continue to explore alternatives to preservation in alcohol, and it may be that advances in digital photography, knowledge about earthworms or even DNA sampling will mean that non-fatal techniques can be adopted in the future. More information about the reasons for this can be found in our Earthworm Recorders Handbook.

Earthworm cast (c) Vicky Gilson
Earthworm cast (c) Vicky Gilson

Do earthworms produce “poo” as a defence mechanism?

We’ve not seen any references to this, and are not sure if this would put any predators off. Earthworms probably just “poo” more as they are disturbed as they move faster and therefore what’s within their digestive track gets expelled faster! However, there is so much we don’t yet know about earthworm behaviour, that who knows!

Worms do have some known defence mechanisms, these include the dropping of their tails for some species and the release of foul smelling liquids.

What earthworms should I use to aid composting? How can I make my compost bin a good place for worms, and is it harmful to the worms to use a compost accelerator?

The species of composting earthworm you’re most likely to find in the UK are Eisenia fetida (also known as the Tiger Worm or the Brandling Worm) and Dendrobaena veneta. They are native to the UK so if you build a composting system they tend to arrive of their own accord, as long as there is a route into and out of your compost bin.

Try and ensure your compost system is roughly 50/50 ‘green’ and ‘brown’ waste.

There are numerous types of compost accelerators, anything naturally high in nitrogen will speed up the breakdown of waste.  This creates heat though, and  the earthworms can get caught and overheat. Also the acidity produced in the breakdown of compost waste can cause the pH to drop to anything around 4.5 and ammonia builds up, which can be fatal to earthworms.  It’d be more ideal to compost and vermicompost side by side, offering them refuge or a reasonable escape route to cooler conditions.

My compost worms have disappeared as the summer progresses and there appears to be an ants’ nest with many flying ants.  Is there any connection?   I know the worms will return as I add to the composter but how? Are the eggs in the composter waiting to grow?

Compost worms may disappear if the compost bin is too dry, to hot, or too acidic.  They’ll start to get uncomfortable after the temperature of the medium reaches 30°C.  It’s important to ensure there is an escape route out of the compost bin, so the worms can retreat to find more comfortable conditions.

If there are ants it means to compost bin is too dry.  Damping down and agitating the medium will disperse the ant’s nest.  In future, maybe add a bit water along with some soaked cardboard or paper, to keep it damp.

The worms will have left plenty of cocoons in the compost that will hatch whenever conditions are ideal and the worms surrounding the system will sense the improving conditions and soon move back in.

Do others have shared observations of earthworms in human biosolid produced soil?

Human faeces used in composting is known as "Humanure" and there are people that swear by it. Composting human or animal faeces obviously comes with risks if a suitable composting system is not used so it's worth seeking more specific advice in the Worm Composting UK - (Worm Farming, Vermicomposting & Vermiculture) Facebook group or referring to The Humanure Handbook.

Will you be holding field events again soon?  If so, where?

Earthworm field sampling
Earthworm field sampling (c) Vicky Gilson

The ESB has suspended our training courses and field events due to the Coronavirus pandemic. We’re keeping this under review, and will release a statement through our members newsletter, website and social media when events are resuming. Unfortunately, we don’t have a date for this yet but it is unlikely that there will be any change until next year at the earliest. In the meantime we recommend keeping an eye on our website and look out for newsletters that will announce any virtual events that we are hosting… like the upcoming SuperComposters UK Virtual Meetup on World Earthworm Day!

Regarding where events will be scheduled… we really don’t know the answer to this yet either. It’s likely that we’ll have events in London, Berkshire and Shropshire as we deliver these in partnership with the FSC BioLinks project. For other locations we rely on being hosted by other organisations that have microscope and teaching facilities.

How can I use worms to improve a new lawn on clayey, rubbly soil?

Try and break up compacted soil to help earthworms move in.  The addition of a thin layer of compost on top of the lawn will also help, as it provides food for earthworms and can help improve the soil structure.

The addition of calcium carbonate too can help improve clay soils, and adding some wood chip can also help.

For more discussion on this it may be worth joining the Worm Composting UK - (Worm Farming, Vermicomposting & Vermiculture) Facebook group and putting your questions to this helpful and knowledgeable community.