Will a Worm Population Double in 3 Months?

Many seasoned worm growers will claim that their worm population will double in 3 months - and they believe it. That seems an extraordinary claim to make, so let's actually work the numbers and see the result. 

So, here's the numbers and  assumptions.

We start with an easy number - 100 Eisenia fetida - the most common compost worm

Then we assume:-

  • Conditions are ideal – 25oC/77oF temps – good moisture,  enough food etc    
  • 4 cocoons produced per adult worm per week
  • 4 juvenile worms hatching from each cocoon
  • 21 days  until cocoons hatch
  • 42 days to maturity
  • 12 week period.
  • we count the cocoons at the end of each week.
  • No worms die on us.

WEEK 1

 100 Adults


WEEK 2


100 Adults
400 Cocoons (A)


WEEK 3 


100 Adults
400 Cocoons (A) – 7 days old
400 Cocoons (B)


WEEK 4 


100 Adults
400 Cocoons (A) – 14 days old
400 Cocoons (B) – 7 days old
400 Cocoons (C)


WEEK 5 


100 Adults
1600 Juveniles (A)
400 Cocoons (B) – 14 days old
400 Cocoons (C) – 7 days old
400 Cocoons (D)


WEEK 6 


100 Adults
1600 Juveniles (A) – 7 days old
1600 Juveniles (B)
400 Cocoons (C) – 14 days old
400 Cocoons (D) – 7 days old
400 Cocoons (E)


WEEK 7 


100 Adults
1600 Juveniles (A) – 14 days old
1600 Juveniles (B) – 7 days old
1600 Juveniles (C)
400 Cocoons (D) – 14 days old
400 Cocoons (E) – 7 days old
400 Cocoons (F)


WEEK 8 


100 Adults
1600 Juveniles (A) – 21 days old
1600 Juveniles (B) – 14 days old
1600 Juveniles (C) – 7 days old
1600 Juveniles (D)
400 Cocoons (E) – 14 days old
400 Cocoons (F) – 7 days old
400 Cocoons (G)


WEEK 9 


100 Adults
1600 Juveniles (A) – 28 days old
1600 Juveniles (B) – 21 days old
1600 Juveniles (C) – 14 days old
1600 Juveniles (D) – 7 days old
1600 Juveniles (E)
400 Cocoons (F) – 14 days old
400 Cocoons (G) – 7 days old
400 Cocoons (H)


WEEK 10 


100 Adults
1600 Juveniles (A) – 35 days old
1600 Juveniles (B) – 28 days old
1600 Juveniles (C) – 21 days old
1600 Juveniles (D) – 14 days old
1600 Juveniles (E) – 7 days old
1600 Juveniles (F)
400 Cocoons (G) – 14 days old
400 Cocoons (H) – 7 days old
400 Cocoons (I)


WEEK 11 


1700 Adults (A)
1600 Juveniles (B) – 35 days old
1600 Juveniles (C) – 28 days old
1600 Juveniles (D) – 21 days old
1600 Juveniles (E) – 14 days old
1600 Juveniles (F) – 7 days old
1600 Juveniles (G)
400 Cocoons (H) – 14 days old
400 Cocoons (I) – 7 days old
400 Cocoons (J)


WEEK 12 


3300 Adults (A) – 1 week old.   These will produce 4 cocoons each =13,200*
1600 Adults (B)
1600 Juveniles (C) – 35 days old
1600 Juveniles (D) – 28 days old
1600 Juveniles (E) – 21 days old
1600 Juveniles (F) – 14 days old
1600 Juveniles (G) – 7 days old
1600 Juveniles (H)
400 Cocoons (I) – 14 days old
400 Cocoons (J) – 7 days old
400 Cocoons (K)
13200 Cocoons (A-1)


FINAL AT END of WEEK 12 


4,900 Adults  which will produce 19,600 cocoons                                                                                                                                                                 1,600 Adults

 ——————————–

1600 Juveniles (D) – 35 days old
1600 Juveniles (E) – 28 days old
1600 Juveniles (F) – 21 days old
1600 Juveniles (G) – 14 days old
1600 Juveniles (H) – 7 days old
1600 Juveniles (I)
——————————–
400 Cocoons (J) – 14 days old
400 Cocoons (K) – 7 days old
400 Cocoons (L)
19,600 cocoons
—————————————————————–

TOTALS 

6,500 Adults
9,600 Juveniles
20,800 Cocoons   

and we started with 100 !       Extend the math a little further just to see what happens. 

Our conditions were ideal and none died.    But, there's nothing to say at various times during a year, your worm bed conditions won't also be ideal and it's very unusual to find worms dying.

But bear this in mind.    A doubling of population, does not mean a doubling in mass.    4000 mature E.fetida may weigh one kilogram, but 8000, being 4000 mature and 4000 hatchlings won’t weigh 2 kilos.