I have been lucky enough to capture the following in a photograph.
Here a large female is laying her eggs, enclosing them in a foamy pouch called an ootheca or egg sack.
When the female produces the ootheca it is soft, and in this case blue....but very quickly it will dry to become firm and quite tough, and in most cases brown. The ootheca protects the eggs until they hatch. Every species of mantis has a different colour, size and shape of ootheca. Our species in Hong Kong can have hundreds of mantis eggs inside just one egg sack.
Here below a flower mantis has just laid her eggs, in a long line on some bamboo.
it is a wonderful experience to watch the many, many tiny little hatchlings emerge and then disperse, so tiny and fragile.
Because we live in a temperate zone, many of the insects in Hong Kong will not live or be active through the winter, and most will begin to disappear when the temperatures fall below 15-18degrees (although some will reappear on hot sunny days).
Our species of mantis need a diapause, (tropical species do not). A diapause is a pause in development in winter, making it possible for the mantis to produce its eggs in fall and have the nymphs hatch in spring. Low temperature will arrest the development of the ootheca.
So the females will lay the ootheca in fall, after which all adult mantises die. The eggs inside the ootheca will rest until spring, when the nymphs will hatch and grow up to repeat the cycle.