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Mealworm larvae and pupae sifter

I am currently designing a 3D-printed sifter intended to separate pupae from larvae. This seems to be the biggest issue for me as my farm becomes larger and larger. Picking out pupae by hand used to be fun; now it's tedious!

I saw a really neat video of an automated sifter which was able to separate most of the pupae from the larvae. From what I could tell it used long rails (instead of the square-shaped mesh we typically use), which were not wide enough for pupae to fall through, but were long and wide enough for larvae. You can see this beginning at the 2:10 minute mark.

Fast forward to my 3D design, I am wanting to know the average width I need for my slots, so that an average sized larva can fall through, but not an average sized pupa. This is assuming that pupae are slightly wider than larvae. I am fully aware there are a variety of sizes and that I won't catch them all, but it's a start!

HERE is a picture of my sifter so far. The only thing I plan to adjust is the slot sizes and maybe their orientation.


  • How will you build this once your design is complete?

  • i have access to a 3D printer where I work :)

  • New design, based on what I've learned so far by searching these forums. I changed the slot orientation and lowered every other slot piece, hoping to help 'channel' the critters into the slots. Now to hit print and see if it works!


  • current design has 3mm gaps. these seem way too small after seeing it started on the print bed. going to bring the unfinished bottom of it home to see if any larvae will fall through. obviously the smallest ones will, but they aren't usually the ones in the bins with pupae! I think I may need to go up to 4 or 4.5mm..

  • Very interesting! I would love to see how this turns out.

  • Looks great, good luck!

  • I printed a test bottom using the 3mm gap. 3mm was barely large enough for a mature larva to crawl into and it ended up just getting stuck. I've since made the gap 4mm and 'rounded' the top of the plastic slots to help guide the worms into the gaps. Currently printing out this new test bottom and will test at home this afternoon.


  • Hi Moofisilla, - Since you have 3D fabrication available I think you may be able to design a separation ramp. Mealworm larvae before pupation will "wander", driven by hormonal titre changes, & I see this in TinyFarm grow bags as larval pile ups in the upper bag corners (& top opening twisted closure).

    Presumably you are rearing in bins & what I envision is installing an incline "ramp" for those larvae at the "wandering" stage to pull themselves upward along. I believe they use some part of their mouth to do that when climb up grow bag mesh; at least that is what black soldier fly larvae utilize.

    Should that work it would mean you no longer have to separate pupae because the definatively last instar larvae will self-separate. Then you are merely directing their ramp to a collection container.

    I have minimal pupae in my harvests because at some point the massing of larvae up in the grow bag top corners/closure knot indicates that pupation is imminent. If I manage my egg collection allowing too many days prolonged then grow bag age mates are relatively diverse & I've to compromise on ratio of wanderers (best developed) vs. non-wandering (grown less) vs. pupae (unwanted except for breedin).

  • I see what you're getting at, but I think it'd be quite difficult for the setup I currently have, since I have so many bins (and plan to triple this in the next couple months).

    I was able to test my design last night though, with great success! Here is the video. I want to print out a complete version of this now, with side walls, and then use it to prototype a wooden version with small dowels (like you all have described in your other thread). My 3D printer can only print so large (10x7"), but wooden sifters can easily be build to handle larger surface areas. I currently use these sifters, which are really effective to sift out frass from substrate from worms, but they just don't separate the pupae from the larvae.

  • @Moofisilla Ooooh That setup looks awesome! How many do you have? How old is your farm?

  • I started back in February with 5,000. I bought another 5k in March and April. I currently get 3-6,000 worms a week. I sell maybe 2,000 every couple weeks, so most of my worms are maturing into beetles. I now have 10 beetle trays (not pictured) with about 1,000 beetles in each. I have a customer who wants to order 140,000 worms at a time in the spring (baby bird season), so I’m gearing up for that.

  • Just an update for anyone interested:

    I am going to a local fabrication lab tomorrow to laser-cut sheets of birch plywood to make these trays. This method is much faster and cheaper than 3D printing plastic filament. I have four different sized designs, and will be selling them publicly if it all works out. I'll create a new discussion thread if anyone is interested. Prices will range from $15 to $50 depending on size.

  • @Moofisilla - that's awesome! Have you also considered setting steel rods or wooden dowels through a frame with the appropriate spacing? Might end up being more work or expense vs. your plan to laser cut the ply, but could be a good solution if it's important to have some bevel on the cross beams in the sifter.

  • One of my many prototypes was a wooden version with dowels. Was fun to build, but I couldn’t get a consistent spacing I need between rods (even though my measurements were accurate. The laser-cut method is my preferred method since it guarantees accuracy.

  • Another update - I now have their designs perfected and on sale at in case anyone is interested!

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