No.
You don't ever really find out, until the eggs hatch, or not hatch in the spring. Because, even if she has not mated, she will still lay eggs.
Males do not lay eggs, females only do and for the eggs to be viable they will need to mate with a male yes.
Male and female praying mantis's act quite different. The females eat constantly to create the eggs inside her body and to support herself. Females cannot fly very well if any at all. On the contrary, males are capable of flying, and they search for females to mate with. They eat smaller bugs occasionally, but really not that much. After the male and female have successfully mated, the female eats the male just like it would eat any other bug. Hope I answered your question, but I didn't know exactly what you were asking. -_-;;
not long after the female and male have mated
You can't tell except by watching them mate. If the female is in heat and there are many males around it is most likely one if not more have mated with her.
No male duck will ever turn into a female duck.
When she is 12 to 14 months of age.
the female is usually the one with ruffled wing from being mated with
Male Seahorses can live with a mated pair Seahorses were once thought to be monogomous but that has been proven false. so the female may mate with both if all live together
Sounds like they just mated!
Because they are probably a mated pair, and she is in charge.
It is best to add another seahorse female to a tank rather than leave a single male seahorse in a tank with another mated pair of seahorses. If the female in a pair dies, simply replace the female seahorse. You can keep several pairs together in a larger tank.