Whatever happened to the mealworms?

Adult and juvenile

Adult and juvenile Tenebrio molitor… and a cauliflower stalk

Well, that was a question that I had been asking myself too. You may remember that I was having a go at raising mealworms as a source of protein-rich food for my hens (details here). I’ve been very quiet on the subject recently because I thought that it hadn’t been successful and I was looking at other options, However, I am pleased to report that the lack of success was only because I hadn’t been patient enough. I decided to tip the contents of my three mealworm tubs into a bucket last week with a view to feeding the contents to the chickens and giving up. However, disturbing them like this revealed much more life than I had thought remained.

Never having had a go at this sort of thing before, I knew little about the ecology of Tenebrio molitor, the species in question, so I wasn’t sure what to expect. I think I may have been wildly optimistic about the speed of the lifecycle… a salutary point about doing your research first! I’ve now done more reading:

The life cycle of Tenebrio molitor is of variable length, from 280 to 630 days. Larvae hatch after 10-12 days (at 18-20°C) and become mature after a variable number of stages (8 to 20), typically after 3-4 months (at ambient temperature) but the larva stage can last up to 18 months (Feedipedia)

All the life stages seem to be present now

All the life stages seem to be present now

So, the fact that I was not seeing large larvae as soon as I expected after raising the adults was certainly because it was too soon. My newly disturbed bucket, in fact, contains lots of mealwormlings, as well as live and dead adults, large larvae and a few pupae. They are currently feeding on rolled oats and gaining moisture from pieces of potato and cauliflower.

In addition, I discover that

Commercial mealworm producers sometimes include a juvenile hormone into the feed to prevent the larvae from molting into adults, resulting in “giant” mealworms that can achieve a length of 2 cm or greater and weigh more than 300 mg (Feedipedia)

A range of sizes of larvae

A range of sizes of larvae

Meaning that I may not be able to produce the big chunky mealworms that are available to buy from pet stores.  I don’t really mind this, because the hens are not fussy about the size of their food! And I suspect that the size issue is important for producers of dried mealworms, because they are bound to shrink with the loss of water as they are dehydrated.

During my recent research I discovered that the species is also known as ‘Darkling Beetles’, which sounds rather romantic to me. Plus, I was amused to read on one site:

Tenebrio molitor larvae are easy to culture (they are often raised on oats, and females lay up to 500 eggs), high in protein, and readily available commercially, so are a good food source for pet owners

But personally, I don’t fancy snacking on them myself!

Anyway, I will continue to care for my colony and see if I can viably produce enough to replace some of the chickens’ feed.

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