This morning I saw four praying mantis nymphs hatching from an egg case that I rescued from a dead flower and kept safe over the winter. I attached it to a chip of wood with double-sided sticky tape, and when I judged the time right I put it in the greenhouse, correctly orientated. It is a biggish, well formed ootheca, probably built at the height of the season. The nymphs were surprisingly large- similar to nymphs in their second instar. (See shot on the left.) That one emerged from one of about 20 cells, eight of which are visible in the left-hand photo. How did they fit?
Their eyes were black, their abdomens fat, and they were semitransparent. They were at least 3mm longer than two-day-old nymphs. Little more than an hour later their eyes were green and they had shrunk, but still they were larger that the two-day-olds. (See right-hand photos, hour-old at the top, two-day-old below. Not true scale.) I don’t recall seeing such big hatchlings before.
A few hours later they had moved on. The ootheca is very close to the door, so I don’t know if they left or stayed in the greenhouse. There could be more to come from that ootheca.