Mealworms going through early cycle

Hi My mealworms are very healthy the problem I have is that it looks like they are going through their life cycle very early. The pupa, bugs and worms are very small. I had this for two months now that I can't harvest any adult worms, we are going through our winter season now but our min temp will be 19 degrees (South Africa). I've tried searching the web but could not find any indication why. Please help!

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  • edited July 31

    Hi Deidre, - Chemical blockade of enzymes that normally degrade insect juvenile hormones' form cause abnormally large larvae to develop (ie: by slowing this hormone's break down). Your undersized larvae are an opposite case, where breakdown of juvenile hormones/signal molecules is occuring too often.

    Normally larvae live with a high base-line level of juvenile hormone modulted pocesses. Then when instar moults the ecdy-steroid hormones are more active & juvenile hormone levels decrease from timely enzyme cleaving, before rising again.

    In simple terms larvae stay larvae under the influence of juvenile hormones & ecdy-steroid hormones/signal molecules require juvenile hormone levels to go down before they ( ecdy-steroids) can shift larvae to get a new cuticle going for transition onward. How long the phase of ecdy-steroid hormone influence lasts contributes to how much new cuticle gets a chance to develop.

    Your larvae cycling along to pupae "very early" means the larvae are getting a briefer than normal time with juvenile hormone inflence before enzymes degrading alot of juvenile hormone kicks in. Then levels of ecdy-steroid hormones get leeway to initiate new cuticle. But in your case, apparently there is not too long a sway of ecdy-steroid processes (which if occurs in pupae a truncated ecdy-sterone phase causes poor new cuticle synthesis that lead to aberations) & eventually a percentage of the larvae are negatively impacted from successive instar stages with minimal cuticle (ex: your runts)..

    The complex of receptors for ecdy-steroids/signal molecules also has parts that juvenile hormones/signal molecules can home in on. Docking at hormone receptors lead to gene expression with influences that work downstream, in this case, to cycle a faster production of the enzyme that degrades juvenile hormone molecules; yet since the enzyme that synthesizes new juvenile hormone can still come along from genes' expression the larvae keep cycling toward pupation even though undersized for instar moving on from.

    Insect research done to control them as pests in the agricultural context has developed different compounds that interfere with the normal life cycle of bugs at different stages by interfering with juvenile hormones. Some are structurally mimmics of juvenile hormone parts &, being not quite normal, bind competatively to hormone receptors at the expense of natural juvenile hormones.

    Once locked on to the receptor juvenile hormone mimetics get gene influences that are not completely normal; which can also include the internally monitored hormone level responsive enzymes. Possibly this happens since the normal larval feedback mechanism of juvenile hormone levels registers the juvenile hormone mimetics' as a higher than normal state; this then triggers the production of degrading enzyme to bring down that false reading of juvenile hormone levels. Based on dynamic described above I think your issue is related to triggered juvenile hormone degradation enzyme over-production as a downstream sequel to artificial juvenile hormone mimetics ingested in their diet. My surmise is there are insect control products used in South Africa used on crops that have gotten into your larval feed.

  • Thank you gringojay, what would you suggest I do? I'm running a wildlife rehabilitation center and the mealworm farm is of the utmost important to the center as most of our juvenile animals feed on them.

  • Hi Deidre, - What are you feeding them? Since my best guess an ingredient you bought when it was growing had been sprayed with what are called a "juvenile hormone analog" try to inquire that likelihood for your raw material.

    Mealworm larvae in their natural state are omnivores. Carbohydrates in their diets are very useful to get good growth, but do not have to be in the form of bran or grain - those are just compact to store & easy to serve up.

    Juvenile hormone analogs are not all the same & depending on when insect exposed the mortality rate is different. The marketed products are usually designed to dilute & aerial disperse to fall down upon plant surfaces for bugs to then ingest.

    Applied diluted over large fields these products are not designed to penetrate plants & then build up inside plant tissue. If you have invested in large stockpile of bran/grain already I think you can batch wash off any residual juvenile hormone analog, dry the portion before it picks up molds & use it.

    I do not know if South Africa has one of these types of compounds developed (or being used "off-label") to pre-treat an item before storage (as distinct from while growing).These are not designed as "knock down" insecticides that kill on contact (more as hormone interupters to alter colony replacement capability) & I presume your mealworm herd still has some surviving to adult beetle stage.

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