You can google 'worms string of pearls' for more than you want to read on this. Much discussion points to cold with a mis identified worm type that cannot handle quite as low a temperature as EF and over feeding.

I did not read enough to form any opinion myself though there are some active members here that have participated in these discussions for some year so maybe they will have some insight to offer but as mentioned these discussions go way back so there is tons of reading available. The first result in the search of the above terms is actually a thread here on GW.

Thanks a lot!
I am just going through the posts in the other thread and no one really knows. It seems to be some kind of random effect with a lot of possible but not clarified causes.
But I am glad that I am not the only one with the problem and that maybe there are some solutions out there... I just have to read more.

So, thanks a lot!

Horst Knotter: Horse Hockey! Sorry your nom de plume reminded me of a cross between Harry Potter and Colonel Potter.

1. That is the best photograph of string of pearls I have ever seen. Not so good for the worm.

2. "chalk in my box" rhymes real cool. Here we call it adding lime. The issue with that is worms can live in this pH and that pH. But what they can not live in is rapid change of pH. Better to just not add lime past adding this mornings egg shells. If one has to add lime they are not doing it right. Those who are adding lime please look away and just keep adding it. If it is working fine for you, if your worms are fine, I'm OK with it. We are talking fairly new bins here. Or at least fairly new worm keepers.

3. You should be getting mega replies here. I apologize. We humans have recently stood on the auction block, been looked over carefully for our generating clicks ability, they may have checked our teeth, been sold to total strangers and harvested. The majority of us are something or other and not posting here. I'm not posting so don't read my post. It is invisible and visible only by people with great pictures of string of pearls. We are not ignoring you new posters with issues we would love to assist you with, we are thinking they are bribing us with candy now but would prefer a more painful method in the future. We are their stock, their herd, their bread and butter, their slaves. We are a commodity. And Facebook vacuums all of our personal information but that is where all the cool posting is now, but still it vacuums and sells our information. So there vacuums too.

4: "no one really knows" Yes, people do know. I might not remember the exact answer. Yes, many have had the same issue to varying degrees. Yes, this is a topic for... some posting question board, somewhere, (We just do not know where yet. Lots of places frequently vacuum.)

5. nexev: valid points.

6. Horst Knotter: "Same of my worms look like pearl chains and they can no longer move the "infected" parts. Some segments of them look fine, and then there is a small not good-looking segment, again followed by a normal segment." Excellent verbal description of string of pearls.

7. Yes nexev they do say it is due to "over feeding". Good research. I'm guessing you would agree it is not over feeding but under bedding that is one of the contributors.

8. What is your bedding? How often do you add new bedding? Could corrigated cardboard be incorporated into the system? How large is the system? A small system could simple be turned into a cardboard box and the box put right back into the original bin. Sometimes at this point vermicoposters grab a tri pronged tool and go threw the bin bit by bit looking for survivors and removing excess food to add to their outdoor compost system. (Throw in a corner of the yard.)
Can you add a shred of cardboard egg carton, not plastic or styrofoam. Mixed with a shred of paper towel tubes. Not newspaper or office paper since I think it makes it worse because it clumps or has bleach or something.

9. Stop feeding. We are guessing the bin has enough food to last six months. Add bedding. Nice bedding. Fluffy bedding. Dry bedding. Is the bin wet?

10. You wrote a great post. Sorry about the worms. We will try to fix this with you. Some of us have been there too. I hope you have come to the right place, although I sort of wish we were somewhere else.

System specifications would help us help you. Indoors, outdoors. Temperature. Moisture Level. Type of worms. From? Food type? How much? How often? In what form? Blended, whole, chopped, rotted, fresh? Type of bedding. How much and how often added? Type of bin? How long vermicomposting? Want to harvest worms? vermicastings? process kitchen scraps? process bedding? The more we know the more we can custom our response to your specific questions and vermi specific needs.

https://www.youtube.com/watch?v=vhagzSEXzic

So About my bin:
The bin is indoors and is a two chamber box made from untreated wood. The dimensions are 55 cm x 45 cm x 35cm. Temperature is 16-20 °C. The worms were fed once or twice during two weeks with partly rotten kitchen waste like tomatoes, carrot skins, apple cores or grapes together with some cardboard or egg carton.
The box itself runs now for ~4 months. The bedding is shredded newspaper. The box is moist but not really wet. I migrated the worms from my old worm bin (wooden box but only one chamber) one week after I put in the bedding and some small amounts of food.

The complete story in short:
I migrated the worms to the new bin. I read that the worms like to breed in hemp so I made a hem proll filled with oatmeal flakes (only a small amount) and cardboard. I also added some lime into that.
Two weeks later I found the first string of pearls victim. Later on I found two more.
To speed up my worm project (I only migrated ~100 worms to the new bin) I ordered 500 more worms (Dendrobaena veneta as before from www.wurmwelten.de <- german vermicompost shop). Later I found a total of 5 victims. In a german forum I was told that this is simply caused by a lack of lime and minerals so I ordered some stone meal and "worm pellets" (wheat with minerals) mixed them with some lime and a lot of cardboard and put it in the bin. The worms seem to like that since the are quite a lot below the spots where I placed the mixture.
But still from time to time I find another victim next to fat healthy agile worms.

Want I want to achive with vermicomposting is to have really good soil for my plants and to get rid of most of my kitchen wastings (which the worms can actually eat).


So I will put more bedding in there and stop putting in lime. Just egg shells from now on.
That might be a first step. I hope I could answer all your questions so far.

I am no expert (I am realy a novice), but I would guess that the lime was too concentrated and "burned" the "string-of-pearls" worms. I doubt that adding lime is needed. If I did feel the need to add lime, I would do so by mixing it with bedding and food is a separate container before adding the mixture to my worm factory.