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Mealworm Pupae Turning Black or Becoming Deformed

Discussion in 'Insects, Other Invertebrates & Arthropods' started by richard22, Aug 16, 2019.

  1. richard22

    richard22 Arachnopeon Active Member

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    Basically, I have been breeding mealworms since Aug 2018, and from around Oct 2018 and until the present day, every mealworm pupa I have had has either slowly turned brown on the wings, and sometimes pupate incorrectly, and very rarely correctly pupated into beetles. I have researched these two issues HEAVILY and I have since noted two possible causes. Here is my basic breeding setup (don’t read if you don’t feel it necessary to understand my issue): sterilite bins, with or without lid (with unventilated lid more beetles seem to hatch); wheat bran substrate, a few fairly thin and halved potato slices switched out every other day; the substrate is not replaced often, only when the frass is noticeable, and I use the same gloves that I use replacing food for other insects [lots, but slight majority roaches] and grain mites have been spotted in SOME small cultures of misc. mealworms but I haven’t seen them in dry and horizontal mealworm containers and mostly in frass. Pupa are normally put onto some wheat bran and not clumped but near each other, humidity would be very normal and same for temps, and finally I take pupa out every other day and not every day.)

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    For the pupa browning, the only possibility I can imagine is they are drying out. I don’t keep them in deserts, and mealworm tutorials don’t say to keep pupa in a humid container, so this is likely not the true cause. This issue is the majority of the issue, except in unventilated and/or humid containers with the pupa, but I was also told pupa need high ventilation and probably don’t need special humidity since this isn’t mentioned much as a consideration of special pupae treatment.
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    The row on the bottom is of the browning pupae, the main issue which seemingly dries out every pupa (but not all get crumbly, most turn dark brown and slightly flexible); the general gradient is from left to right. The top two are the healthy ones, note the one on the top with the red appendages, it will probably pupate correctly at this rate. The one on the top right is the deformed beetle type, it barely limps around and has a very empty abdomen and the wings have not developed correctly.


    For the deformed pupation, I have read the pupa may need to be treated with extreme care to not interfere with hormonal responses. Once again, this consideration, to treat pupa specially, is not commonly mentioned. Hormonal changes could be from elsewhere..

    Here on, I am going to try to rule out some possible roots of the problem:

    My ‘eureka’ moment was when I thought the pesticides in the produce I fed (potatoes or carrots) could be causing these issues. I came to a dead end with this not being mentioned as a big deal when breeding mealworms, I basically had to rule this out because these issues aren’t incredibly widespread. I did read from a knowledgeable entomologist on another forum that a fungi-insecticide (known at Bt) could be causing all sorts of hormonal issues, but I have made some experimental mealworm runs with different produce (potatoes, carrots, organic potatoes, organic carrots, collard greens, and banana peels) and I am unsure if the differences between the 31 mealworm trials would be correlated to the produce. This could explain all the issues, but once again is unlikely since it is not associated often in any regards. Though I did never wash my vegetables, possibly keeping pesticides, but once again same goes for the first successful beetles.

    I can easily rule out the vendor question, I got all my worms from Petsmart, including the successful batches that resulted in a healthy beetle batch that lived for 3+ months for a few individuals. Maybe I just got incredibly lucky or seasonality of the mealworms made so that only Aug mealworms weren’t hormonal altered. Perhaps Petsmart could have made changes to the mealworm breeding and that could have carried over to me, I don’t know.

    I can also somewhat debunk temperature or humidity concerns. Mealworms are known for NOT needing high heat to hatch and breed, same for humidity (I did successfully breed my first culture of worms into beetles in late summer to mid autumn) and their worms had the issues from there and the same goes for the subsequent attempts. Season is even less possible, the temps and humidity in autumn when I bred successfully would be replicated through spring and get better in summer too.

    There is one potential to consider that the entomologist posted, colony cross-contamination, with what I don’t know, maybe zootic diseases or parasites. I always used the same gloves for all my insects, and all insects were located in my dining room until I split the cultures into my hot attic for my crickets, roaches, and waxworms and left the rest. Regarding changes at the time, I was doing little special at the time to my knowledge, I was trying to breed house crickets to no avail (constant virus mass death), my mealworms, and finally my variety wild-caught insect vivarium, containing isopods, field crickets and sprickets later, and scarites ground beetles. It died off from the soil being too dry and compact, and one black field cricket killed off the rest of the weak sprickets and isopods.

    Enough rambling, I have some ideas to put out there for the ACTUAL reason this is happening. There were two or three major changes I made after my first beetle batch, I started feeding potatoes instead of carrots (more surface area) and started using wheat bran instead of oatmeal, and possibly I could have continually ‘cross-contaminated’ my cultures beyond that point as my insect arsenal increased gradually and moreso in 2019; I can pretty much rule out the carrot to potato suspicion since I have tested some mealworms with carrots AND organic carrots, so the issue is likely not that. The wheat bran suspicion is the only other reasonable conclusion I can come to not involving pesticides or disease, if anyone knows of other root causes I could be having, I will listen closely. Cross-contamination could be and issue, vague but it might explain the hormonal issues I assume the mealworm pupa are having.
    I am planning on a penultimate trial, opposite of how I normally breed mealworms, in my hot attic, purchased from another vendor, not fed produce and only sponge for moisture, and kept clean, mold free, and treated with a new pair of gloves for changing the produce and they will be isolated from the other bins. This should tell me some important things, but I still need some ideas from the community if possible.

    For more info on my issue, you can read my thread on openbugfarm.com with a knowledgeable entomologist who had trouble ‘diagnosing’ my issue definitely, though they lastly mentioned the cross-contamination: http://www.openbugfarm.com/forum.ht...worm-pupation-issue-and-mass-cricket-die-offs