Mass Mortality of Chinese Mantis: 62/65 individuals dead over the weekend

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ArcticMantis

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Hello,

I've been raising Chinese mantises (Tenodera sinensis) in my lab for 5 months now. They were all L6-L7, not yet adults, because I needed them for experiments in January so I was feeding them weekly and keeping them at about 22 degrees Celsius. Over these 5 months, I have left them alone every single weekend, and they have always been fine. However, this morning (Monday) I came into the lab to find all but three of them dead. They were all doing fine on Friday.

Most of the dead are in the lying-on-the-back, legs-up death pose, but others are upright on the bottom of their containers (but dead). Only one had a moult skin, and none of the others seemed to have had a failed moult of any kind. the back portion of their abdomens, near the anus, was dark, but I find this isn't uncommon for mantises that die from anything. The humidity was still 66% when I came in, so it wasn't too dry. 

I had them on crickets before, but a few died, so I switched to mealworms, which I have been feeding them for 4 weeks now. I recently bought some new mealworms at Petsmart, because it was the only place I could find them that wasn't a two hour trip away. I fed the mealworms some apple after I fed my mantises. I considered the possibility that Petsmart sold me tainted mealworms, but there doesn't seem to be any vomit or diarrhea in the containers, so that seems unlikely. Also, I was feeding them on a rotation, 1/3 on Monday, 1/3 on Wednesday, 1/3 on Friday, so I feel like if the deaths were food-related, it should have happened in waves.

I suspect it might be temperature related. Where I am, it went below -10 degrees Celsius outside this weekend (as it has the last few weekends). I don't have a heat source set up because the heat is supposed to run in the lab through the weekend. I've emailed the maintenance board to see if the heat was interrupted at any point over the weekend, due to repairs or perhaps a malfunction, but they say their records have the room between 19 and 22 degrees all weekend. They also said that no cleaning was done over the weekend.

I mostly want to know what happened so that it doesn't happen again. I put a lot of hours into these mantises, and I didn't even get a chance to use them in my research before they died. I would hate to raise more mantises, putting a lot of time and effort into them, only to have them die in the same way.

Does anyone have any ideas of what went wrong? 

 
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@Synapze, I asked the maintenance board about that. They said there hadn't been, but they also said they'd get back to me with more information. I don't think there was, since I work with other bug people (in a different building) and we like to gossip about different insect infestations that happen in town/ on campus. Plus we bug people are hella paranoid about pest treatments happening near our bugs (for good reason!) so we're usually kept in the loop on that... but sometimes things mess up, so it's hard to say

 
@ArcticMantis The temp range is a little on the low side, but nothing a Chinese mantis can't handle easily, so it's safe to rule that out. Considering the staggered feeding schedule, it's probably safe to rule out feeder contamination. If maintenance is absolutely certain the temperature remained in the 19°-22° range, chemical exposure is the only thing I can think of. 🤔 I'm so paranoid about chemicals in my bug area I don't even spray deodorizer nearby or use any cleaner that has a strong smell.

I can't imagine your disappointment. 😕 If you find out what happened, please give us an update. 

 
Mealworms are usually kept in bran when I buy them, I’ve had problems with the substrate moulding in the past after feeding fruit to them.

 
That is a puzzle for sure. My two cents is that I am rather convinced that I have had mantises die from eating BSF that have been fed apples as maggots. I have not had enough mantises to do a proper experiment to confirm this but its happened at least twice and I could not find any other issues.

That said you have no idea what petsmart was feeding those mealworms or how they were kept before you bought them (mold). Other then pesticides being sprayed or temperatures as you have said that's the only thing I can think of. 

Mealworms are insanely easy to culture yourself so it might be time to do that so you can control what they are eating and how they are kept and rule out contamination for your next round.

 
The mantis died from something with the mealworms. I am sure of that. also they need to eat more than once a week. Three times minimum. it won;t kill them not

to eat, but it is not enough food for them . The temps were a little low, but that did not kill them either. I would think with the low diet they were not healthy enough

to survive the poison the mealworms may of had. If they were fresh hatch I could see such a die off, but not at this stage. Also they should of been adults at 5 months. I believe the diet may them slow down and be behind in becoming adults. Please do not take this the wrong way, all living things have their own way of living and

we have to learn about that to take care of them properly. I had a lady once who had adult chinese who only fed them 3 to 4 hydei each day, can you imagine that?

Also I raise my mantis on flies only and occasionally get a worm of some type as a treat.

 
hibiscusmile said:
The mantis died from something with the mealworms. I am sure of that.
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If it was due to contaminated feeders, wouldn't it stand to reason that the 1/3 fed on Monday would've died before the 1/3 he fed on Friday? How can you be sure? Is this common with mealworms? 

 
Good point, but the mealworms fed on the following days, would of been more toxic as time went on. Do you have any mealworms left? and if so

how are they? Mealworms fed on carrots or crickets we have seen make mantis sick for some reason, not sure why but there is lots of post about

carrots on here, but who knows exactly what the meal worms were fed.

 
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hibiscusmile said:
Mealworms fed on carrots or crickets we have seen make mantis sick for some reason, not sure why but there is lots of post about

carrots on here, but who knows exactly what the meal worms were fed.
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I agree, and suspect the same. DeShawn has written about it. Yen has advised me on it. Yet on Mantis Keeper, some Bad Hombre fed his mantis a chunk of boiled carrot, and it survived. 😆

 
My feeder roaches feed on carrots and there’s never any problem. Any feeders iv had suspected problems with in the past have been crickets, morio worms and meal worms, which are all raised on bran. Veg like carrots go mouldy fairly rapid compared to fruit with the exception of tomatoes. The toxicity of the mould would build up for sure over the days. Has the possibility of a sunbeam coming through the window and hitting the enclosure been ruled out ?. I know it’s winter but the sun can still double temps in a matter of minutes when coming through a window and it’s coming in at different angles as the sun lowers everyday over winter.Chinese mantis can handle high and low temps, if the temperature rises to quick maybe they wouldn’t fair too well.

 
The Carrot topic is a very debated one for sure. My personal opinion is that it is more an Urban Mantis Myth then truth. Crickets are well known for causing disease and death in mantises if their husbandry is incorrect or if they are already infected with viruses they can pass on (some species are more susceptible) and I think a few people fed their already contaminated feeders carrots and then assumed that was the issue. Since we all love our mantises so much we are willing to just take carrots out of the equation just to be super safe and that general fear has been spread about.

I have never had any issues with feeding carrots to any of my feeders. Non organic apples, maybe, carrots never.

Again this is just my personal opinion, not using carrots is not a major drawback if there is any chance at all it might kill your mantises.

 
I myself had problems and lost mantis when I received crickets fed on carrots, only those fed crickets either died or were sick. The crickets

were ok when I gave them potatoe and other items to eat and refed them off after a week, but that was just my experience. I like the window

suggestion, that could also be it.

 

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