Nymphs dropping like flies

[SkittishMale]

I hatched out a wild-collected Mantis religiosa ootheca that I collected last Autumn and had stored in the refrigerator at 5 degrees Celsius. It was put in the fridge in the first week of October and was taken out to incubate on the 5th of January. It hatched right after 4 weeks of incubating at room temperature. What I found odd was that they didn't all hatch at once and instead, some hatched each day for most of the week. I started with roughly 80 or so nymphs after it hatched and they were given D. melanogaster and D. hedei fruitflies. Most died and now I only have around 10 nymphs left and they look like they're ready to molt to second instar hopefully.

My two questions are, why didn't the babies hatch simultaneously? and why did almost all of them die? I am aware that many of the hatchlings of this species, like many other mantises that hatch large amounts of nymphs, die or eat each other soon after hatching. I've raised this species before a number of times and never had this many die in first instar. Even some of the mantises that fed with visible size put on their abdomens died too. Was it just a bad ootheca I collected? Has anyone else had an ooth where almost every mantis died?

 

[MantisGalore]

What were the conditions after hatching ? What were the conditions of the hatching container (substrate,etc...)

 

[aNisip]

Sometimes when nymphs "just die", it can be a result of bad genes, but it's usually because of the conditions. 1st instar nymphs are the most fragile and if certain conditions aren't being met, they will quickly tell you by dropping dead. To help figure what could have been the cause for such a major die-off, it would be helpful to know the conditions they were under the whole time after hatching, like MantisGalore stated above. 

 

[SkittishMale]

They were kept on moist papertowel as substrate and kept in a plastic shoebox enclosure with mesh put on the lid for ventilation. I've used this exact setup before and never had an issue. The temperature was room temperature. I found out that the ooth probably wasn't refrigerated long enough because I've had better results when I had the ooths in the fridge for the whole duration of winter. This ooth that didn't work out was taken out of diapause sooner because I've had success with doing this in the past. 

 

[jrh3]

this is one of the reasons they hatch so many. there is always alot that will not make it to 3rd instar.

 

[PlayingMantis]

Last month I had a catastrophe with orchid nymphs dropping dead like flies. Some dropped dead after hatching, while others couldn't make it to L2, couldn't molt, and died. Factors I attributed the deaths to: 

-bad genes (I've been breeding them sibling-to-sibling for 3 generations)

-temps too low

-humidity too high

-excelsior bought from the craft store might've been contaminated(?)

-going on vacation and having someone else take care of them

 

[Brian Liang]

Just last week the wild-caught M. religiosa ooth I had also hatched and they did not come out all at once as well so it may just be a normal occurrence in the species . . . not sure why they would all die though

 

[CosbyArt]

From all the wild collected ooths I've hatched they all tend do the slow/split hatches normally, although a few will hatch one main hatch. That includes the native species in my area Stagmomantis carolina and Tenodera sinensis. It also seems to apply to the same native species ooths I got from adult mantids I kept, if I do not diapause them too - perhaps even more so.

I've found if I have kept the ooths diapaused 5 months or longer, they tend to hatch in one main hatch (including wild ooths I collected near spring). I've done just short of 4 dozen ooths now so not enough for definite test results.

Also it is said 15-24% of nymphs survive to L2, at least with native species. If you had larger losses the two most common problems are humidity (not enough or nymphs being trapped in water droplets), and lack of Melanogaster flies leading to more nymphs to cannibalize (I find they need fed almost daily, as they will eat more than expected).

 

[hibiscusmile]

I still dont know why they die off like they do. I am finding to much misting (each day) seems to be one problem, lack of flies not it.Maybe to many flies, stress them

out? Still no real clue.

 

[Rick]

The deaths sound typical of my experience with that species.