Encouraging Pupation

I wanted to share some observation about the cycle change from larvae to pupae and what I've noticed helps speed up the process, and to get a discussion with other's ideas about how to accelerate the pupation so that if I want 600 beetles, or 1000 beetles in a tray, I can acquire that number of pupae quickly.

I've noticed that when the larvae have a clean environment (little frass buildup, no dead larvae / pupae) and adequate nutrition and moisture (yeast, carrots) they tend to pupate more quickly. I've also noticed that there seems to be an exponential curve to the number that pupate maybe due to the presence of pheromones of previously emerged pupae. Maybe it's good to leave the larvae and pupae in the same bin so that these pheromones encourage pupation.

I was hearing that a strong magnetic field might have some sort of biological response in mealworms and that it might be possible to get a mass pupation by using something like a cattle magnet in the tray with the larvae.

Do others have additional information about speeding up the transition?


  • @double_ott - I know @gringojay has posted elsewhere about the relationship between presence of frass, juvenile hormone, and delayed pupation. I don't recall all the details off the top of my head, but I believe it aligns with your observation. Don't know about the magnetic field, would be great to hear if anyone has any insight or knows of good research on the topic!

  • Hi double-ott, - At about 10,000 times (320mT) the normal northern hemisphere (22.5nT) magnetic field the research team of Prolic & Nenadovic found a range of 1.3 - 6 days faster emergence of adult Tenebrio molitor from pupation. Any seasonal change in magnetic field did not seem to alter this trend.

    Half the pupae (30 fit in the 19 mm gap between the arms of a 64cm X 40cm magnet) under 320mT magnetic field emerged on 16th day. In contrast half of the pupae under natural magnetic field emerged after 19 days. Authors's calculate an average of 13.6% less time is required to complete pupation under their tested magnetic field.

    A cow magnet is designed to adhere nails & range-wire pieces swallowed into the cow reticulum; so this magnet has to be swallowed & I think a common magnet size is 8cm X 3cm X 1 cm. Although there may be larger cow magnets it seems they won't cause the level of magnetic field that advances adult emergence almost 14% sooner.

    The reported precise days to adulthood is to be considered indicative of a pattern & not absolute numbers of days - since study design deliberately did not use "optimal" life cycle conditions. As per (1995) "The influence of a permanent magnetic field on the process of adult emergence in Tenebrio molitor", originally published in Journal of Insect Physiology, Vol.41(12)

    Prolic with Nenadovic & 3 other associates years later reported that the same 10,000 times stronger magnetic field than normal accelerated T. molitor pupal incipient neurons (cell & nuclei size, how many nucleoli in a nuclei) and corpora allata (size, cell number) development. Pupal data was collected by euthanizing them once had 8 days of existence. See (2007) "The effect of a static magnetic field on the morphometric characteristics of neurosecretory neurons and corpora allot in the pupae of yellow mealworm Tenebrio molitor ..."; originally published in Internation Journal of Radiation Biology, Vol. 84(2)

    Their results indicate the 320mT impact on corpora allata led to the synthesis of juvenile hormone, which had abated at end of larval phase & whose (juvenile hormone) resurgence is required again just before insect is to hatch into an adult. In early days of pupal stage the juvenile hormone is not being produced.

    Authors mention other Prolic/Nenadovic research that although the high magnetic field pushed pupation to terminate faster the "... adult lifespan was short...." Report presented at Tesla Millennium-Fifth International Conference in Belgrade (1996) titled "The effect of the static magnetic field on the life span of the insect Tenebrio molitor ...."

    Elsewhere in Forum the effect of frass component farnesol as a promoter of juvenile hormone synthesis is discussed. If juvenile hormone levels can not go down the transition into pupae takes longer, even though juvenile hormone must go up inside a pupa at a later stage in order to eventually emerge as an adult.

    Prolic, et al. discussed how an increasing magnetic field can increase calcium ions (Ca++) inside the developing neural cells; then the action potential of those neurons is increased & changes like they noted can occur. Conceivably dosing the pupae with calcium could do this, although I am speculating & assuming using something like the penetrating solvent DMSO with calcium painted (or sprayed) on the pupae.

    For that matter, possibly farnesol in DMSO used on the pupae would be another tactic; & maybe even one could just use larval frass (for it's farnesol) dissolved in DMSO. Pure farnesol is likely expensive but one can still try to make an extract from their own grass & evaporate off the fluid to collect the solutes.

    Another solution may be to isolate the pupae & loosely bury them (once they are pupae) in pure frass, although I think it unlikely they would absorb the farnesol fraction that way it may turn out to be what you envision occurring by keeping larvae with the pupae. My inclination is that since mealworm larvae "wander" when ready to pupate their natural instinct is to get away from the herd & this means they do not want to be with younger (non-pupating) larvae because they need to shut down juvenile hormone production in order to perform their early stage pupal changes.

  • edited January 14

    Farnesol, which can be in 4 different isomers, is the molecular formula C15H6O composition called 1-hydroxy-3,7,11-trimethyl-2,610-dodecatriene. If you want to increase farnesol in larvae to delay pupation (ie: keep them marketable as larvae) then in theory you could divert it from sterol production by using the 15 carbon farnesyl pyro-phosphate involved in that pathway (made from the 10 carbon geranyl pyro-phosphate via enzyme farnesyl di-phosphate synth-ase).

    Clotrimazole is probably the cheapest compound to try (as opposed ketoconazole, fluconazole or miconazole) & an experinental dosing level that should be safe is 0.5-1.0 microMole clotrimazole; whether the dose can be increased for a desired reaction would need to be investigated with trials. If misted on food the drug's solubility in water can probably be enhanced by adding 0.5% (by volume, vol./vol. of water) of the surfacant Tween 80, which should have no adverse effect when it (Tween 80) is ingested by a larvae.

    When administered, this compound (clotrimazole), there will be less (according to my theortical extrapolation) of the internal 15 carbon molecules made into squalene to move the carbon along in the sterol pathway. Instead that carbon will go toward synthesizing farnesyl-ated proteins ("RAS") &/or 20 carbon molecule geranyl-geranyl-ated pyro-phosphate (which is turned into geranyl-geranyl-ated proteins "Rab &/or Rho" &/or geranyl-geraniol) plus the 15 carbon molecule farnesol.

    Whether or not this same intervention with cloitrimazole (should it play out as I project) can be used on pupae to also cause them to synthesize farnesol, which might then provoke their premature (for pupal stage) production of internal juvenile hormone is another issue. Since pupae have no method of ingesting those "azole" compounds (developed as anti-fungal drugs) they would need to be passed into the pupae; (again) my best guess of a carrier vehicle would be DMSO (as the drug's solvent).

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