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Ultra Cheap Mealworm Production



  • @gringojay - lots of info, and many thanks for sharing. Amino acid balances are, as you mention, a complicated issue in feed formulation, and many of us with less background could benefit from deeper reading! Can you share some sources, whether books or scientific papers, to help us more fully appreciate the implications of the info you've shared with us? Thanks!
  • Pardon omission of acknowledgement for my 1st post: here is basic 1975 source from Canadian G.R.F. Davis' "Essential Dietary Amino Acids for Growth of Larva of the Yellow Mealworm Tenebrio molitor L."
  • Would adding fluffy sawdust help increase air flow into the substrate and allow for increased depth without harming yield?
  • edited January 2014
    Potentially! There are a few things acting to restrict the number of mealworms you can put in a tray:

    - Airflow. They need to exchange gases.
    - Heat. They can overheat from friction due to movement if too packed together without environmental controls.
    - Waste removal. I at least vaguely remember a study showing that mealworm growth is affected by presence of their frass? If this is accurate, frass needs to be cycled out of the system somehow. The more worms, the more frass buildup. @andrew, am I making this up?

    Just like humans, really.
  • When spoke of dry peanut meal, this is defatted peanut- a byproduct leftover from peanut oil extraction. In small scale operations a manual expeller press will separate out the oil since want to limit oil in mealworm's substrate.
    "PITEBA" (& similar manual presses) can be found online, while PITEBA has data for it's % oil extracted. There are even oil presses made from pistons for rural development.
    How much & when to supplement with peanut meal needs to be determined.
    Largely because of it's higher magnesium content of 3.6mg/gram defatted peanut meal, as opposed to oat meal's 1.4mg/gram.
    Insect's initially fed high magnesium have to deal with the accumulation of magnesium before their counterpart to our kidney, the malpighian tubules. Larvae don't have blood, but hemolymph & before the malpighian tubules develop to deal with the magnesium the hemolymph loads with excess magnesium.
    This leads to stunting growth, yet when magnesium level is boosted 30 times greater after about the 3rd day in Drosophila larvae that were then 3rd instar stage there was no counterindication - in fact amount of protein in their fat bodies improved.
    The magnesium paradox is best detailed in 2010 "Drosophila TRPM Channel is Essential for the Control of Extracellular Magnesium Levels".
    Authors elaborated (quote): "...during early larval development...high Mg...suppresses feeding behavior and growth of ...fat bodies...a prerequisite for anabolic function...once morphogenesis...largely complete...high Mg...contribute to Mg resorption in...fat bodies...promoting biosynthetic function."
    Which refers us back to Davis' 1975 diet for mealworms which supplemented the feed substrate with zinc. The TRPM (transient receptor potential melanstatin subgroups, )in insect is different than our multiple TRPMs & insects respond to zinc by improving their metabolism of magnesium.
    2010 "TRPM Channels Mediate Zinc Homeostasis & Cellular Growth During Drosophila Larval Development" discusses how inadequate zinc downregulates TRPM forming up.
    Authors make the point that (quote): "TRPM deficiency... reduction...larval growth ...decrease in cell size... defects in mitochondrial structure and function...cell size and mitochondrial defect can be rescued by extracellular Zn(2+) supplementation."
    Frass excretion is also likely to improve with zinc, because a robust TRPM function is crucial to managing the magnesium involved in excretion of worms. See 2008 "TRPM Channels are Required for Rhythmicity in the Ultradian Defecation Rhythm of C. elegans."
  • A commercial mealworm flow chart from van de Ven Insectenkwekerij in Netherlands can be found as "Figure 1" in this link:

  • Crowded mealworms perform a sort of quorum sensing of the herd. One result of too high density is cannibalism; intriguingly another cause of cannibalism is too low relative humidity.
    Meanwhile they prepare themselves for fungal load by producing melanin. A way to judge if or how overcrowded herd is getting is how dark (degree of melanin)they are getting.
    Without crowding & good aeration the metabolic rate of cells rises, which decreases a cell membrane's electrical potential. If the oxygen pressure in that cell is steady there is less ROS (reactive oxygen species) generated; whereas hypoxia (low oxygen) & also elevated oxygen pressure will increase ROS output.
    When melanin is made it spins off ROS & quinones that must be dealt with. Brewers yeast in the substrate helps supply extra factors, like guanine & cytosine that are ameliorative.
    ROS impacts sperm & ideally an egg bunch laid will hatch by day 12 if ambient temperature is at minimum 20* Celsius. Commercial temperature for fastest larval growth is 25* to 27* Celsius; at 20* they trundle through more instars/molts.
    Data shows a lone mealworm's larval phase will last ~140 days, weigh ~103 mg & only suffer mortality rate of 3%. In contrast the crowded mealworm's larval phase is shorter at ~115 days, weight ~117 mg & suffer mortality rate of 24%.
    Although individual weight is higher when crowding it should be understood that larger larvae generate more heat to the herd. Humidity control (min. 13% to max. 70% relative humidity is feasible) becomes more important because at low range the larvae can eat normally but not actually gain mass.
    Basically larvae retain more weight in the higher viable range of relative humidity & they have rectal glands that absorb ambient moisture. Their butting up against the carrots pushes the carrots down into the substrate & should be monitored if the immediate relative humidity of that substrate rises above 70% before fungal conditions can arise that imperil the larvae.
    When relative humidity is more than 70% ( even if no fungal growth establishes) the larvae will consume less - but they will plump up with fluid volume rectally absorbed. A factor of approximately 50% more weight is achieved when larvae are at top range 70% relative humidity than when reared at 30% relative humidity.
    Since we are here concerned with protein value it should be explained that the longer the larvae grow &/or bigger become does not equate to more % of protein content by dry weight. Younger larvae are essentially more protein rich, just less mass; furthermore, because of different rearing humidity larval moisture studies ascribe 58 - 67% as their water content by fresh weight.
    The question of effectiveness in energy conversion by larvae of the food spent on growing them is worth mentioning. At a protracted phase in larval growth, somewhere when aged 50 days at, they may be bulking up but using their food less efficiently.
    On crowding see: 2000 "Density-dependent Prophylaxis in the Mealworm Beetle Tenebrio molitor L: Cuticular Melanization is an Indicator of Investment in Immunity"
    Regarding herd signaling: 2001 "Characterization and Cloning of a Tenebrio molitor Hemolymph Protein with Sequence Similarity to Insect Odorant-binding Proteins"
  • Hey @gringojay, some great info and great references - thanks!

    We're currently trying to figure out a way to avoid moisture feed (carrots, etc.) getting "lost" inside the substrate; it's a sure source of mold problems. I like the idea of keeping carrots in a mesh bag that has sufficiently large holes to allow mealworms to pass in and out. This would make it easier to keep track of the pieces, but moving carrots in and out of a bag isn't time-efficient process.

    Aside, I read a good paper regarding optimal harvest time recently - I'll try to track it down.
  • dansitu, optimal harvest time would be great to know. Meal worms can be harvested soft after shedding or crunchy just before, but I can't imagine how you could sort these.
  • Fras: I have heard it is a super plant additive for growth and can be sold... any thoughts?
  • " gain of water from the food only occurs in humidities above 70%..."
  • Frass has short chain fatty acids that can inhibit seedlings even though improve germination rate. Frass does not serve the same purpose as worm castings (which can be used at any time).
    Late-instar frass per 100 grams contains butyric acid = 0.0889, plus propionic acid = 0.0279 g, plus valeric acid = 0.0175 g.
    Protein in diet alters the larval commensal bacteria resulting in less hydrogen/CO2 shunting, which leads to lower levels of short chain volatile fatty acids in frass. Also, with protein (commercial breeders use defatted soy) the ratio of butyrate relative to propionate & acetate in the total frass is greater - although the total concentration is less.
    Furthermore, the larval gut bacteria alter over time; with mostly Enterococci when new. With growth the diameter (volume) of the larval gut rises in ratio to the surface area of it's gut & anaerobic Clostridia establish as well.
    They also have Lactobacillus, like L. brevis & L.plantarum: it would be very easy to innoculate the feed with L. plantarum (found on vegetation) to try to manipulate the frass utility. Aged cabbage (think of it as a pro-biotic, since L.plantarum is sauerkraut's fermenter) has been incorporated into mealworms feed incrementally from 1 gr/200 larvae to a maximum of 5 gr/200 larvae by day 30.
    Mealworm larvae will congregate in response to the lactic acid in frass. They are repelled by high levels of valeric acid & butyric acid.
    Experiments with wheat seedlings showed frass solubilized fertilizer grew 5.8 cm length of root (vs. normal 11 cm length), shoots 4.6 cm (vs. normal 7.7 cm)& a low fresh weight of wheat seedling of 0.15 g (vs. normal 0.2 g).
    Regarding fatty acids in agriculture see:
    " acids ... germination inhibition... damaged root meristematic tissue...inhibition of cell division."
  • Thanks gringojay - will be processing that info for the next few weeks!!! You are brilliant.
  • edited January 2014
    To follow up on @gringojay post - while the results from the studies showed that the frass compounds inhibited seedling growth (an additional interesting resource on that here:, from personal experience when used as a fertilizer, amended into the top inch of soil later in the plant's life, works quite well for herbs and leafy vegetables. I have also amended into soil when up-planting mints, sages and oregano and had very happy plants. Unfortunately I haven't had the opportunity yet to run a controlled comparison of the same plants in the same stage up-planted with and without the frass, but it's a very interesting area for further investigation and particularly interesting what processing could be applied to the frass to increase it's value
  • Success with frass on established plants is possibly due to a combination of soil microbial web plus the way short chain fatty acid oxidase enzyme (which can process the short Acyl-CoA chains) only comes on line in plant roots after a span of days & can in time upregulate in sufficient quantity to handle the frass volatiles in a dose dependent fashion.
    (Quote:) "...Short-chain acyl-CoA oxidase ... abundant in 5-day-old Arabidopsis etiolated cotyledons ... roots... whereas very low levels ... in 7-day-old green cotyledons, rosette leaves, and stems....":
    More about frass:
    (Quote:) "...mixed with soil ... highest yield ... ratio of 1.5% ...effects ...on photosynthetic rate,nutrient concentrations... not significant...improving ...productivity ...not only by ...mealworm excrement but also by other factors."
    from "Effects of Different Application Amount of Yellow Mealworm Excrement on Growth and Quality of Rape"
    (Quote): "... N, P, K and C/N ... dry frass ... are 3.66%, 1.40%, 1.62% and 9.86 respectively... frass are composted for 10 days, then the water logged compost are mixed with sandy soil at ratio of 1∶40, it results the plants of mungbean to gain 17.9% more weight than those of the control plants, this is the best combination of treating the frass to be a fertilizer"
    from "Study on the Fertilizer Efficiency of the Frass of Tenebrio Molitor L."
    ((NOTE/COMMENT: here frass is 1st composted, which subjects it to microbial modification))
    (Quote:) ... ratio of 1:160~320 (bulk ratio) were optimum to culture vigorous seedling..."
    "The Effect of Different Application Rates of Defecta of Yellow Meal Worm on the Quality of Cucumber Seedling for Breeding"
    ((NOTE/COMMENT: this is a significant dilution of frass; worm castings are used in germination as 30% by volume of the growing substrate for optimal results & in transplanting at 20% by volume of the growing substrate))
    One of my previous links appears inoperative, it is for Brazilian journal Cienc. Rural vol.31 no.3 Santa Maria May/June 2001: "ASPECTOS FISIOLÓGICOS E CARACTERIZAÇÃO DA TOXIDEZ DE ÁCIDOS ORGÂNICOS VOLÁTEIS EM PLANTAS" ( Physiological Aspects & Characterization of Volatile Organic Acids Toxicity on Plants)
    ?How long does it take for mealworms to excrete frass ? Depending on temperature & ambient factor the "lesser" mealworm seems to average 1-2 hours for gut transit (as per "Evaluation of Salmonella Movement Through the Gut of the Lesser Mealworm" in journal VECTOR-BORNE AND ZOONOTIC DISEASES Volume 12, Number 4, 2012)
  • Really excellent resources @gringojay - continued thanks for your contributions and synopsis of the literature!

    I should also mention that the frass I use with my plants is rarely fresh, usually it has sat around in a bag for at least a couple of weeks, up to a couple months. I'll have to find the source on this, but I recall that the fatty acids oxidize fairly quickly, and this could have some significance, and perhaps related to the findings in the above source:
    "(Quote): "... N, P, K and C/N ... dry frass ... are 3.66%, 1.40%, 1.62% and 9.86 respectively... frass are composted for 10 days, then the water logged compost are mixed with sandy soil at ratio of 1∶40, it results the plants of mungbean to gain 17.9% more weight than those of the control plants, this is the best combination of treating the frass to be a fertilizer"
    from "Study on the Fertilizer Efficiency of the Frass of Tenebrio Molitor L."
  • A question:... Is the Darkling (great word!) beetle - which is the beetle that produces meal worms - edible as a beetle? People are all about the worm, but perhaps the beetle is good to eat after it has lain the eggs. I'd hate to just throw them away. Or... are they otherwise at least to feed my chooks? :-S
  • Andrew-
    regarding frass "effects ...on photosynthetic rate,nutrient concentrations... not significant...improving ...productivity ...not only by ...mealworm excrement but also by other factors." My speculation is one of the "other factors" is that frass volatiles influence the soil microflora to produce a volatiles that act as plant growth stimulants.
    Beta-carophyllene, a sesquiterpene volatile, stimulates plants to increase (upregulate) their cell wall loosening expansins ~4.5 times more than normal in roots & 6.5 times more in leaves. Likewise the volatile dimethylhexadecylamine from specific rhizobacterium boosts plant biomass by ~1.5 times.
    Soil emitted volatiles reach the plant cell's gate plasmolemma instigating signals transducing plant genes to respond. And as one would expect, the beta-carophyllene is good in moderate amounts; but when too much worsens germination/root/aerial growth.
    The same bacteria can emit volatiles that act as growth inhibitors when their growing medium is more mineral & yet act as growth elicitors when they are in more carbon. To optimize a strategy it is worth considering that the build up of fertilizer salts in the root zone shifts the microbial volatiles' spectrum away from growth elicitors - even if plant is already so big it can not be stunted.
    Certain soil bacteria produce the volatiles 3-hydroxy-2-butanone ("acetoin") & 2,3-butanediol (a 4 carbon alcohol) which improve drought tolerance/aquired systemic resistance/growth. Plant friendly fungi lower the immediate pH with the acidic secretions the fungi solubilize their fungal nutrition with & some of the bacterial symbionts of fungi can only survive if the bacteria can tolerate the acid pH swing.
    Those bacteria ferment molecules to adapt & then the butanediol is the byproduct the bacteria gas out as a volatile.
    Some fungi host on their outside an ectosymbiotic consortium of bacteria that emit varied spectrums of the currently identified 300 bacterial volatile organic compounds.
    The range of impact for some of these volatile is increase in length of plant root/shoot/fresh weight/chlorophyll content - so frass potentially offers a unique factor.
  • Oh gringojay, I can't follow it. Only because my brain is different. You are a scientist-minded person and I am more arty... what you are bringing to this discussion is fantastic. So thank you. This info will help others but it's tricky for me... if you can, could you put in a bit of earthy home-town version? You don't need to if you don't work that way.
  • I bought a heat-mat for when the weather gets below 18 C. (25 c = around 78 F). can I safely bury it in the oats (2cm deep) on a plastic floor? It is small -handspan- and 10 watts. :-*
  • @dansitu I put the carrots inside the egg case not touching the substrate. I saw this tip in youtube videos and I am trying on my mini-farm.
  • @kerri, the adult darkling beetles are safe to eat, although they apparently don't taste great. I've never tried! Chickens would probably still like them, though.

    I wouldn't bury the heat mat in the oats - just for safety, it's usually best to keep them isolated from the thing they are heating by something non-flammable, like a sheet of glass. Your best bet is probably just to follow the guidelines in the manual.

    @allan, let us know how it goes!
  • Thanks Dansitu, The guidelines were pretty sparse on the heat mat, so I'd rather play it safe... glass is a great idea.
  • Allan, I do that too with the carrots and potato, it's easier to look out for mould, and I think they last longer that way too.
  • @kerry do you know if instead of paper egg cases, we use some kind of plastic case the effect is the same? I mean, mealworms are not negatively affected by the plastic cases?
  • They're not bothered by normal food-safe plastic, as long as there's enough grip for them to climb on (if they have to).

    We generally don't use egg cases, etc. with mealworms - we just drop the food on top of their regular food, but try not to give them enough that it goes bad before being eaten. Egg cases are used a lot with crickets to give them a good place to hide away.
  • Hmmm. Egg crates. I noticed that my meal worms are eating some holes in them, so I wonder if that's not good for our food, or am I being way too fussy here? So, that cardboard may contain chemicals to bind it etc, but it is digested in the tract of the bug and transformed. Also - in minuscule amounts.
  • No reason not to use plastic cases... they bugs just want to hide after all, and they are OK with the plastic boxes they are in.
  • As Dan mentioned, we avoid using paper egg cartons because the bugs tend to chew on them. This is primarily a traceability issue, it's pretty much impossible to know where the paper that was pulped for the egg tray came from, what inks/dyes/contaminants it contains etc..

    Although we do not have positive evidence that paper egg trays do contain nasty chemicals or heavy metals, we're weary of depending on them at this early stage. However plastic or styrofoam trays should be no problem. Just be sure you wash them before introducing to your bugs as there is a real risk (in the US at least) of salmonella and other bacterial contamination if you are re-using a grocery store egg tray.
  • @andrew, apart from washing items introduced into the breeding environment, they could also be frozen for a while I suppose.
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