# Mealworm Pupae Turning Black or Becoming Deformed



## richard22 (Aug 16, 2019)

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.





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


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## richard22 (Oct 18, 2019)

Update: the mealworms I buy at Petsmart tend to have dark colored areas in their bodies, and when I dissect them where their white inards should be there is this soy sauce substance. Even if I tried another vendor I am already sick of wasting my money of trying to breed mealworms and have since lost all motivation to keep trying, so I am just doing lesser mealworms now, same ones used to clean roach enclosures. Unfortunately they smell like ammonium and attract scuttle flies since I only have holes as ventilation but atleast they actually live and breed normally. I guess I could use them as food, but selling potential is unlikely. Based upon my experience, never buy mealworms bred from petsmart, even for petfood, and don’t expect success when breeding mealworms regardless of how many tutorials you follow which never address these issues. Infact, just don’t buy anything from petsmart, petsmart is trash. Try it maybe once or twice but don’t keep wasting your money like I did; same goes for crickets, all crickets, house crickets or banded, they’re all the same. Same also goes for superworms.


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## Draylynn (Feb 21, 2020)

Some breeders inflate their worms with hormones - This should become less evident over time as you breed them out: If you're breeding for human consumption, never eat the first batch or two. Don't let the deformed beetles breed.

Reactions: Like 1


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## richard22 (Feb 23, 2020)

Draylynn said:


> Some breeders inflate their worms with hormones - This should become less evident over time as you breed them out: If you're breeding for human consumption, never eat the first batch or two. Don't let the deformed beetles breed.


So should I just buy a 1000 mealworms and hope some of them do okay? I have taken some minor tests and about 1/30 made it beyond pupae phase, but food made basically no difference and the group where I didn't provide food or even move that much did the best.


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## Draylynn (Feb 24, 2020)

Be careful buying huge batches: Believe it or not, some mealworm breeders are clueless to shipping, if they ship them together in bags, they can (and often do) crush each other under their own weight, overheat and die (this is the worst smell on the planet). I'd ask them first if they ship them in isolated boxes or not, especially if you live somewhere warm and you're buying more than 500g.
Don't worry about colony collapse, unless you're using mosquito netting or other toxic materials around them, chances are, it's all down to sifting out the bad genetics produced by mass-production for profit. Eventually, it'll pan out on it's own, but you can help speed up the process dramatically.

- Chuck the deformed newly-hatched beetles (deformed legs, wings, etc - You don't want to pass these traits to the offspring).

- Chuck the small pupa's (if you want big worms/beetles).

- Usual (you should know already) carrots/potatoes etc... Some fresh garden greens like parsley, lettuce, cauliflower, broccoli branches etc or even boiled garden lawn grass (to kill any parasites) can also help.

- Non-toxic bush/tree branches and thick bark soaked in boiling water for 10~20 mins (fresh branches), also work really well. Pat them dry after soak and throw them in with the worms. Sticks tend to dry out within 24 hours, so I rotate batches, whilst they're feeding on one batch, I'm pre-soaking the other in a sealed glass jar, and vice versa. It will take them some time to chew completely through all the sticks, the bark gets eaten fairly quickly(you'll notice they've stripped the bark and smoothed the wood within the first day). This seems to be my worms most favourite thing ever, within mins of these entering the tank, they're all above substrate and clinging to the bark/branches, it's quite something to see and hear.
Note: I'd split the branches lengthwise down the middle, as the little blighters tend to burrow the soft center and are hard to get out when you want to switch the branches out. Mine seem fond of butterfly tree branches, no flowers, no leaves.

- Add cardboard paper or card to the tanks (unbleached, no ink), several pieces about 1/3~1/4th the size of the tank, layered - If you're tanks anything like mine and they're generating quite a bit of heat, add some card. They'll spread out (helping lower friction-generated heat) and climb it/chew it. Especially if your tank isn't in a fairly dark/pitch black area (they hate light). It will also help soak up excess moisture. Place hydration food on top of the card/paper layers (I usually aim for 3 layers, hydration on the second layer, covered over for darkness) - Pupae tend to form in the substrate, distracting the worms away from them will benefit everyone.

- Make sure to check your worms regularly to remove the pupa's (I tend to do this at least once a day). If they get nibbled on by the other worms it can cause damage, that can start a dark spot (wound) which spreads (that 'soy sauce' you mentioned is decaying flesh and guts), and kill them.

Soggy black worms usually indicate they're well hydrated but died for other reasons: Cannibalism, having their legs chewed off, bad bedding conditions (too much poop) etc... Drowning: If you're using a plastic tub and the sides are getting moist enough to form any droplets, if that droplet rolls down on top of a worm, they'll drown and die. In this case you do want drilled breathing holes in the top of the lid or the upper sides of the tank, alternatively, just remove the lid completely.

Consider putting your pupa's in a plastic container with holes in the top and a piece of damp cotton wool in the corner of the box, somewhere in a dark room/cupboard with 19~21C temperature ish location. Especially if you're seeing pupa's turning grey (not black) and not responding.
The 3 whitey's at the bottom of your image look like general defects which could be associated with your breeding source, these tend to die and turn grey or if they make it to hatching, can end up deformed, even fail to shed and die - Just chuck em, feed em to the birds or something.
Worms or pupae that die through poor hydration or fairly complete cannibalization tend to be more dried out, grey or brown. Black ones to me, indicate they died quickly and they were not dehydrated or fully cannibalised. The blackness is all their 'mushy' insides rotting - Blackie may also have been partly-cannibalized by a baby worm (if you're mixing larvae ages), who drowned inside of it or escaped before clearing the inside completely.

NOTE: This information is based on my experiences and observations.

My first store-bought batch, I lost a lot. Out of 500 worms, at least half of them were deformed or failed to hatch.

Out of the last 500 'harvested' pupa's, I've had maybe 1~2 turn grey and separately 3 deformed beetles. I say harvested pupa's, because there are some that fail harvest because of cannibalisation, so that's like.. maybe another 10 per batch that get eaten, I mean, clearly eaten, missing heads, holes in them, etc.

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