Beetle replacement schedule

I've been trying to determine my beetle replacement schedule. I need to know when to let some of the mealworms pupate to keep my beetle count around the right amount.

From another thread on this forum, I need approximately 300 beetles for the size tray I use. -

Beetle lifespan is 8-12 weeks. I'll use 8 to be conservative.

I use a weekly/every-other-week tray rotation schedule. If the beetle survives 8 weeks, to maintain 300 live beetles I need to replace approximately 37 beetles per week. If I let ~40 pupate per week, then process the remaining mealworms, that should get me stable at 300 beetles after 8-10 weeks. At that point, ~40 will die per week, and be replaced by ~40 new pupae.

Is this strategy sound, or should I do a complete replacement of 300 beetles every 5 weeks (factor in that it takes 1-2 weeks for the pupae to become a beetle, another week before they begin laying eggs).

What do others do to get fresh beetles??


  • Hi oskizzle, - Elsewhere in Forum mating beetles have been discussed. For example see treads: "Beetle max population & frass amount" mentions egg laying tapers off after about 3 weeks; "Beetles life span" mentions percentage of egg hatching declines after 4 weeks; ''Utra cheap mealworm production" brings up the point that eggs from older beetles produce heavier larvae.

  • How do you let the worms pupate? My worms seem to pupate whenever they want -.- How do you control when they pupate or not?

  • Hi Carni, - Pupation for all larvae will never be after the exact same number of instars for every larvae that hatched from an egg on the same day.This is discussed elsewhere in the Forum with reference to a study's specific temperature & humidity.

    To delay pupation keep juvenile hormone levels up; which commercial operations do by purchasing juvenile hormone to add. Frass has a compound in it (farnesol) that elicits juvenile hormone production in larvae &, in theory, you could transfer larvae to a feed substrate with a lot of frass mixed into it; thereby retarding pupation.

  • Ok thank you. Population density does not influence pupation?

  • Hi Carni,- Mealworm larvae in high population density initially experience a greater growth rate than at low density. However, after ~ a month the larvae at lower density will experience greater growth rate; with maximum growth rate usually thoccuring when they are 60-65 days old.

    At lower density the survival rate of larvae in the colony, their larval weight, their weight as a pupae & the proportion of pupae emerging as adults is greater, than at high larval density rearing. At high density the larval inclination to "wander" seeking a pupation site creates conflicts as they collide with others also wandering & this possibly contributes to the fact that mealworms reared at high density exhibit some delay in pupation, in addition to lower pupal weight, than those reared at lower density. Once they are an actual pupae the duration of pupation does not seem to be affected by their rearing density (if we can extrapolate this detail from research on the "lesser mealworm").

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