Plagnum (Plaster + Sphagnum) springtail enclosure

This is a 3d printed mesh that can be set into a deli cup with a layer of plaster on the bottom, to form a compartment with spaghnum moss, for culturing springtails.

I've used this setup with great success for many species of non-arid springtails, including Folsomia candida (temperate white), Coecobrya (tropical pink), Hypogastruridae, several species of Pseudosinella, Neanura growae, Sminthurinus quadrimaculatus, Desoria trispinata, certain species of Lepidocyrtus, Isotomurus retardatus, etc.

Not recommended for most semi-arid or arid springtails, such as Entomobrya unostrigata, any of the various Orchesella species, etc.

The plaster and sphagnum hold plenty of moisture to keep the air quite humid for the springtails for a long time, without needing to add more water (months). And harvesting springtails from this setup is quite easy. Since the moss is fully contained in the little mesh compartment, you can just dump some springtails out when needed.

Additional items and materials

You will need 2x square m3 nuts, and 2x m3x8 thin-head screws.

These are the ones I use:

• https://www.aliexpress.us/item/2255800885711092.html (M3 x 8mm)
• https://www.aliexpress.us/item/3256805317845882.html (M3)

You will also need a deli cup. I've provided models for 3 different deli cups.

• 16oz polypropylene (PP) – e.g. https://www.amazon.com/gp/product/B079VYK8TB
• 16oz PET - e.g. https://www.amazon.com/gp/product/B0BT9L5P13 or https://www.webstaurantstore.com/choice-16-oz-ultra-clear-recycled-pet-plastic-round-deli-container-and-lid-combo-case/127DM16COMBO.html
• 24oz PET - e.g. https://www.amazon.com/gp/product/B0BT9KLBMK

And finally, you will need some plaster of paris and powdered activated charcoal. A big bag or one of the smaller tubs of plaster of paris from the hardware store is fine. If you want to order it online, I've used this one and it works fine:  https://www.amazon.com/gp/product/B077MD57S3

For the activated charcoal, this is what I use – https://www.amazon.com/gp/product/B0722T3FXC

I'd also recommend a .1g or .01g scale. Just a cheap one from amazon is fine – https://www.amazon.com/gp/product/B00ME8VI34

Slicing instructions

.2mm layer height with normal settings is fine. No support needed. The side piece should be printed upside down.

IMPORTANT

You need to insert a pause at 6.4mm, just before the holes for the nuts are covered over, and insert the 2 captive nuts into the side piece.

Part Selection

There are 5 total models, with a side part and a top part each. The tall/short variants have a different height of the sphagnum container. The shorter variety can be helpful to avoid  escapees when you open the bin, for species that are particularly “jumpy”.

There is also an optional plaster retainer that you can use, that helps hold the plaster in when you turn it upside down. 

Instructions

1. If using the optional plaster retainer, drill or punch a 3mm hole in the bottom of the deli cup. You want to drill it somewhere on the middle flat part, but not near the center, so it doesn't interfere with the placement of the vertical mesh part
   • Insert a screw through the hole, with the head on the outside of the deli cup
   • Insert the nut into the retainer and place it onto the screw, with the nut facing upwards.
   • Screw in the screw to pull the retainer down tightly against the bottom of the deli cup, so plaster doesn't leak out when you pour plaster in.
2. Attach the top printed part to the printed vertical mesh with 2 m3x8 screws
3. Weigh and pour 30g of water into the deli cup
4. Add 58.8g of plaster and 1.2g of activated charcoal to the water, let it wet out, and then mix it with a stir stick until it's a smooth, even consistency.
5. You can optionally bang the deli cup onto a hard surface repeatedly, in order to settle and flatten the plaster, and help any bubbles rise and pop.
6. While the plaster is still wet, insert the combined side+top printed part into the plaster. You want to push it all the way down, and push the round top part against the side of the deli cup. It should stay put once it's been inserted and positioned.
7. Wait for the plaster to cure. You can leave the deli lid off, or just lay it loosely on the top without fully closing it. I usually wait at least an hour. Sometimes more, or even overnight.
8. Once the plaster is cured, unscrew and remove the top piece, and then place some damp-but-not-saturated sphagnum moss into the back, and then screw the top piece back on.
9. Optionally, add a small vent to the lid. I like to make a ~¼" hole and cover it with surgical tape
10. Add springtails, and sprinkle a little bit of food directly onto the plaster. Keep an eye on how much they are eating – ideally they should eat all of the food within a day or two. And then just add more food every couple of days, as needed. And the springtails should quickly start reproducing and will eventually become very populous.

Note: The attached source files are fusion 360 python scripts that use the fscad framework. See fscad.org for more details.