What happens to the Nematodes during winter months in Dallas? Do they die, or, can they survive our winter months?

Also, I understand that there are several species of Nematodes. What type of Nematodes are good for getting rid of fleas, ticks, all critters that live in the grass of yards or dirt in gardens? Where are you purchasing yours from?

I get the ones from Colorado.

I don't know how long they will live. Moisture and food would be limiting factors.