Mantid Nymphs dropping like Flies

[Serle]

I had a late season ooth hatch on Feb. 3 after being diapaused for 8 weeks .(cool indoors 10 c)

Approximately 50 to 60 nymphs hatched. They have an abundance of Melanogasters to eat and are kept at 25 c.They have been dying at a constant rate of 5 to 8 per day , but not killed by others . Any thoughts or solutions ? 

I am now a a population of 30 ... S

 

[CosbyArt]

@Serle The only other thing not mentioned that could be the cause is their humidity level, or called room humidity (usually labeled as RH% on humidity gauges/meters - hygrometers).

A likely cause especially with winter as heaters further dry the air causing humidity levels to drop, in many homes to 10-25%. Without a species listed I can't refer you to caresheet data, but most mantids need about 50% humidity levels (and is more critical in early instar nymphs).

If they are kept well hydrated with proper humidity levels too, kept within a safe temperature range, plenty of prey, lots of room and places to hide from cannibalism, then the only other cause is weak nymphs. I won't pretend to know the cause, but some ooths I've hatched from the many batches now occasionally all the nymphs are rather weak and sadly near impossible to get more than a few to adulthood.

 

[Serle]

@Cosbyart   I thought that weak or premature nymphs may be the cause . The ooth hatched 8 days after coming out of dormancy 8 weeks .

RH may be low , I am changing some criterion. ...  Thnkz for the feed back ... S

 

[hibiscusmile]

What species? If chinese, they die off in big numbers, so do religiosa

 

[CosbyArt]

@Cosbyart   I thought that weak or premature nymphs may be the cause . The ooth hatched 8 days after coming out of dormancy 8 weeks .

RH may be low , I am changing some criterion. ...  Thnkz for the feed back ... S

No problem and best of luck with the babies.

Indeed as Rebecca said some species are more prone to birthing problems/die off than others. I do know the Chinese mantis (Tenodera sinensis) can have about 70% survival or better if conditions are optimal and are separated before L3 (when cannibalism takes over even if overly fed). When I first started hatching ooths I tended to them every few hours and I had high success rates, and at times anymore I still wonder why my hatches were better than sometimes my best efforts anymore.