If the P eggs hatched in spring, their F gen will hatch in 2 weeks.
If the P eggs are hatched in Summer/Fall, their eggs will go into diapause. Simple as that. These are what they call bivoltine.
But sometimes we don't get uniformity in diapause. I think it has to do with the hybridization of the silkworms of today. Most of the time, it is a bi and a single voltine cross breed. When you incubated the P eggs in fluctuating temperatures, the F egg neurosis sorta takes it on its own to determine whether it wants to hatch or hibernate. Some hibernate, and some don't, as we have seen often. Personally I think they received mixed signals. Imagine if this happens in an egg factory.. but of course, it never will because they exercise precise temp and humidity control.
A skilled person can manipulate the P eggs by shortening/lengthening day hours vs night hours, and giving them specific temp to mimick the seasons.
However, this isn't true if you are working with chow, as the silkworms also take their queue from the nutritional values of the leaves. I don't work with chow very much so I have not reached this part.
So, with the eggs that your moths laid, some will hatch and some will hibernate.
How do you tell them apart?
All eggs are laid creamy white (with slight diff amongst lines).. they will turn darker over days. In general, if they remain same, they are not fertilized. But some times, (again, I think it is the hybridization) and I've seen this in my own rearings, some eggs develop head pigmentation= a small dot near the tip, but is still creamy.. and then it turns darker.. Those eggs are guaranteed hatch. Within the same group of eggs, some of them simply turn dark color without visible head pigmentation, but they end up hatching. Some will remain that dark brown or dark purple color and go into diapause.
What should you do then?
Like I said, in an egg factory, egg incubation is precisely controlled. For example, you can incubate bivoltine eggs at high temp in the spring, and they will lay hibernating eggs. Lab workers forcibly turned this strain to be single voltine because single voltine strains give out the best and highest yield in silk. But the bivoltine nature in them helps make them hardier.
Now, when your moths lay eggs, you technically should also give them temperature treatment but gradually lowering the temp day by day. But that is something we can't usually do in a regular household, unless it is fall season. But it is recommended (by experts and researchers) that you leave them out in room temp, for at least one month. Those that are meant to hatch will have hatched, those that are meant to go in diapause, will have done so completely, by reaching stage 18.. .. after at least one month, you can then put the eggs in 40F fridge crisper in a ziploc and they will be good to catch after 2 months. The longer you leave them there, the lower the hatchability. You shouldn't store your eggs for more than 2 yrs as it weakens them .. 3rd 4th and 5 yrs get even more drastic, maybe as low as 10%.
If you have a lot of moths laying eggs, you'd be better off leaving all the eggs out for 1.5 to 2 months, let them all catch up to a certain stage in the embryonic development, giving the later eggs a chance to catch up.. then store away. When you remove them from cold storage, you incubate them and black box them, they will hatch out pretty much at the same time.
There is a lot of advantage in having them hatch at the same time. The laggards and late molters are very laborious to care for and are usually the first ones to go due to excessive pathogens as they have less resistance to germs and viruses than the larger ones, not counting the fact that they are easily bruised and crushed by layers of food.