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Sorting mealworms

Is anyone available/willing to share your method of the routine sorting necessary for mealworms? I'm finding it pretty time intensive to pick out pupae, dead worms, and dead beetles.

I have a small hand sander hooked up to a tray holder, the trays I have use a bug mesh for finer sifting, and a larger mesh for grabbing out the potato scraps. Do you use a filter as well, if so what size mm is your mesh, do you have various sizes?

I'm needing to scale up, but the processing time is going to just increase and I'm looking for opportunities for efficiency. Thank you in advance!


  • Hi oskizzle, - Take a look at low tech method of YouTube video title "Cleaning live mealworms from dead and grain'.

  • edited July 2017

    To get the pupae away from the dead larvae consider how the pupae are wider & those dead don't flex. By sifting these 2 through a horizontally slatted grill, rather than perforated mesh, of suitable width will let the thick pupae be held up on the slats & dead larvae slip through. Take a look at close look at this kind of grill in 24-30 second mark of YouTube video titled "dead worm&mpupa separate vidio."

  • I actually commented on "dead worm&mpupa separate vidio" earlier today to try and get the dimensions or name of the bucket. Do you know what that sort of 'grill' is called, I can dig up the average size of a pupae and try to find a good option online that has the right size.

  • Hi oskizzle, - I do not know the size. If you don't find a thin enough slatted grill it should be possible to make your own. My thinking is assembling round wooden dowels (or long bamboo meat skewers) spaced to trap width of pupae & then creating rigidity with some outter frame; add cross-linking dowelss/skewers tied in to fix spacing desired between slats. Some hardware stores sell metal rods (hollow or solid core) in assorted diameter & aluminum rod is lightest weight (easier cleaning rod too); the rods' cross-linking can be wire twists (cut at underside).

  • @gringojay, the video shows a great way to sort on a small scale. Have you seen any commercial scale sorting other than the suggestion you posted before?

  • @samglickstein - commercial scale sorting is achieved with standard industrial vibrating sifters and a stack of screens. Try googling for USDA + mealworm sorting - they have had some projects on the topic and there's a powerpoint floating around the internet somewhere with pictures.

  • @andrew, thanks! I'll definitely check it out.

  • So, I already know the optimal harvest weight of mealworms is around 100 mg, but what is the correct mesh shize for seeving these? So in an automated seever that the full growns don't fall inbetween the seeve, but the little ones do?

  • Hi YOMANU, - Here is what I think is happening with automatic siever machines. Firtst of all my impression is the mealworm farmers are not dealing with larvae that have very different sizes.

    In other words the commercial operations take what the breeding beetles lay their eggs in away from the breeding beetles after only a few days. A large scale operation would probably do this by the time 3 days (72 hours) passed, or even sooner 48 hours (2 days) passed.

    This way the surviving larvae at harvest are not very different in size; thus the desired work of mechanical sieving is only to get rid of plant matter & dead larvae. Exactly how the farmer decides when to sieve is probably less based on weight & more on getting the the job before any pupae come along.

    My impression is that the batch of larvae is poured into a vibrating hopper to shake the unsaved lot downward. The 1st screen encountered is likely so wide that the larvae (dead and alive) fall through, yet has a mesh size that will trap any pieces of bulky plant matter fed them - but not carbohydrate feed particles (nor frass excrement).

    The separation of these component possibly employs a side to side or bouncing up & down motion of the screen. What falls through is then further separated using a finer mesh that lets the fine frass particles go thorough but not the larvae (live and dead).

    I imagine there is a short path of travel directed over rollers to redirect the work product within the confines of the machine body. This would allow some cascading action so that an internal fan blowing across the down fall can winnow away the light grain/flour/bran particles as gravity causes just the heavier larvae (live and dead) to fall onto the next mechanical part.

    At this point I think vibration is applied to a conveyor of the larvae (live and dead) & the live larvae flex/wiggle in response to that stimulus; they are thus not elongated straight out. In contrast the dead & dying larvae have no muscle tone; these are thus bendable.

    Thus once the machine gets to just processing larvae subjected to vibration when those larvae are conveyed over a rolling edge they fall (creates increments of feed through, not one big pile up) upon a vibrating screen sized for them. In regard to the screen mesh size used to collect cleaned larvae I think that is determined by the way they are reared & in reference to the batch of age mates to be harvested at a desired age.

    The dead larvae flop about & will passively fall through the screen because they have no rigidity. But the live larvae will be curled enough so they can not fall through that size screen mesh when they bounce up & down (vibration).

    After larval separation into live or the dead/dying the living have to be moved out of the way so more can undergo separation. I think the separated living are again conveyed along to where they can roll off into a bulk collection bin accessible for emptying without dismantling the machine housing. Possibly there is also a 2nd pass of those initially sorted out as dead, whereby those presumed culls are processed through a little tighter screen in order to catch any of the live larvae that might have fallen through.

  • So weird.. I saw this thread right after I posted a similar thread on this topic. Maybe the video I linked to can help shed some light on our dilemma..

  • and the dude replied to your youtube comment - 3mm is the space inbetween rods. This is the info I needed for my design..

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