That tank is kinda odd for mantids. I think it's mostly due to the lid, which only seems to have little air slits, keeping the humidity high. It also doesn't look like it's very suited for a mantis to hold on to.
I would personally just take it off, cover the top with flyscreen and use a desk...
The differences are miniscule. Care is the same for both and in terms of looks it's hard to even tell them apart.
If you want a really big species you could look into Plistospilota guineensis.
Springtails only eat stuff like mold, fungi, decaying matter and poop. They certainly didn't attack them.
What stage are the ghosts in? 20x20x30 for 6 is quite cramped in later stages. Even if you didn't notice changes in abdomen size, cannibalism sounds like the most likely cause here. You...
The care of H. membranacea and S. lineola is the same. They are both hardy species that also look very similar.
The "standard look" mantids from the Mantinae subfamily are generally pretty sturdy without much special requirements. Some other genera that are in captivity include Rhombodera...
One successful mating is enough to supply a female for the rest of her life, though the number of nymphs hatching will probably decrease with each ooth. If you have a male available you can mate them again after every laid ooth.
I'd say L3 is too early for most mantids to reliably tell the gender, only certain species have clear differences that do not involve counting segments. Deroplatys species start forming different shapes of shields from L4 on though.
Have you been keeping them together for a longer period of time? If so, it's possible that they did mate overnight. It sometimes helps to put the male into a different room for a few days so he's no longer in contact with the pheromones. ~2 months is already old for the male though. They get...
I can't really tell from the picture, it just looks like you're holding the left one closer to the camera. Mantids do grow a bit between the molts too, so if it is some time ahead of the second one that could be the reason for the size difference.
Starting at L4, D. desiccata can be pretty easily distinguished by the shape of their pronotum.
Left is a female, right is male. Females form kind of a M-shape, which seems to show in your pictures as well, especially the 4th.
That's completely normal. Some mantids got colors on their segments that are only visible during threat displays or after they have eaten a lot.
Here you can see it on a S. lineola male during mating. It's slightly visible on the female as well.
Hemolymph does not contain any hemoglobin and therefore does not look red like our blood. The reason it appears brighter in preperation of molts might be due to the mantis pumping in more air in order to burst open the carapace and slip out. If you're feeding it a lot until the abdomen is...