From what I understand the egg is already produced and fertile before mating. And since they can produce over three cocoons per week (198 per year) in peak mature conditions. That's up to every two days using the reserve of sperm until it's finished, that's about a 48 hour turnaround, including initiation, hardening of the mucous, and shedding:

"After being joined for up to three hours, the worms separate. The mucus
on each worm begins to harden as the worm starts to back out of, or
slough off, this ring. During this process seminal fluid, ovum and
amniotic fluid are deposited into the mucus ring. As the ring passes
over the worm's head it seals, forming the lemon-shaped, yellow-colored
cocoon. Over a period of weeks, the cocoon hardens to a beautiful ruby
red as hatchlings mature."

Red Wiggler Reproduction

Cheers,

PC

"Cocoon formation started within four days after mating
had occurred...at a constant production and incubation period of 25 C...incubation time of the cocoons varied from 14 to 44 days with a mean of 23 days..."

http://www.tandfonline.com/doi/pdf/10.1080/02541858.1988.11448096

from one study with strictly controlled conditions and close observation of the worms.

Interesting study.

The experiment did not measure precisely the time from mating to first cocoon, the objectives were more to quantify cocoon production and reproductive lifespans. The 4 day figure was an educated guess, and it is only expressed as "less than 4 days". IMO it's said that way because they think it is 2-4 days in this study since they had about 2 cups of moist manure with 10 worms inside which they disturbed on day 60, 70, 72, 74, 76, etc.

Another criticism is that with that kind of disturbance the worms will be freaked and this can affect their reproductive cycle (which includes as they shed their cocoons).

Unfortunately the authors do not report carefully observing the time of
mating, and are vague about clitella development (sexual maturity marker) saying only it happened
between day 60 to 80 for all ten worms in the experiment. They critiqued their own study about not
providing any new food after the start of the experiment for 60 days. They seemed also to suggest diet played a role in cocoon output rate. Day 60 they swapped some new cow manure (food was strictly moistened ~20
day old cow manure) in after which worms started to gain weight
healthily and many matured by day 70, and all by day 80. They did
not check for cocoons until 70, but when they did, they found a few.
They continued checking then every two days, day 72, day 74, day 76,
...

It was an excellent study on the worm life cycle, but given they found rates better than 3 cocoons per week, if the question is how long after mating the first cocoon is, I think the jury is still out and 48 hours seems more reasonable to me in conducive conditions. It was interesting that approximately three weeks after estimated mating, cocoon production appeared to max out at a cocoon every day and a half.

The related question is how long till the last cocoon still generated from the same sperm is shed and sperm no longer viable or all utilized, that could be months. On the other hand worms are extremely content to have multiple copulations and preserve their personal sperm bank, according to multiple sources in the literature, so in a dense worm bin you would expect to get results sooner due to the orgy environment.

Best

PC

Thank you all. who'd have thunk it. untill my son and i started reading up on worms to me a worm is a worm is a worm....... but they are so fascinating.

i will never be able to hold one without gloves on nor hold a big handful as i have seen so many times on youtube.

but we are going to doing it. I am doing it and the more i learn i just have trouble getting my head around it all.