Mealworms are great for chooks, fish or reptiles (and blog authors…) to snack on. They’re easy to breed and need relatively little care, preferring to get on with their lives in relative darkness.
Mealworms are the larval stage of a black beetle called ‘Darkling Beetle’, Tenebrio molitor.
In the wild, the beetles can be found in warm and dark environments such as beneath logs. Its genus name, ‘Tenebrio‘ means ‘one who likes darkness’.
Darkling Beetles are scavengers who feed on decomposing plant or animal material. In man made environments, they can be a pest, living where we store grains and grain which they’ll happily eat (and they eat a lot).
The Darkling Beetle is an holometabolic insect (yes, I had to look that one up) meaning that has distinct forms during each stage of its lifetime. Tenebrio molitor has an egg, a larval, a pupal and an adult (beetle) form.
I couldn’t take any decent photos of mealworm eggs. They’re tiny and white and sticky, forming little clumps. The eggs can take on some of the coloration of the material in which they were laid.
The female beetle lays 100 to 200 eggs at a time and up to 500 over her lifetime. The eggs then take from 4 to 19 days to hatch. In the conditions found in most homes, it will take about a week for them to hatch, into larvae.
This stage is what most folks are familiar with and call a ‘mealworm’.
Mealworms start off very light brown or creamy color and darken as they age. This stage takes 3 – 10 weeks. Mealworms are very active and feed on a variety of foods. They molt up to 20 times as their innards outgrow their exoskeletons. storing up energy for the next stage. After the last molt, the larvae normally darken, curl up and change form, becoming pupae.
This stage of the lifecycle lasts for a period of 2 – 3 weeks but it may be longer in cold conditions. During this stage, the pupae seem inactive but inside their hard shell, all of the complex structures of the adult beetle are forming.
The new Darkling Beetles can mate and lay eggs within two weeks and live for a couple of months.
Over time, a lot of Beetles have escaped and eggs been deposited into Ligaya Garden when I’ve been cleaning out the Mealworm Towers. They’ve successfully grown through their lifecycles and we often find Darkling Beetles under pots and logs. The interesting thing I’ve noticed (and, yes I know that ‘correlation is not causation’) is that we have almost no Earwigs in our garden. Other gardeners curse large numbers of the pests, especially last year when they were out in droves but I had to search around the other day to find one to photograph!. The Darkling Beetles are found where the Earwigs should be. They don’t bother the Slaters any, which is a good thing. I’ve never found any actual Mealworms in the garden though. Maybe they are too quick for me or too well hidden but they must be there because the Darkling Beetles are. Maybe they’re providing food for larger, garden dwelling critters too – I hope so!
The Darkling Beetles and Mealworms will live quite happily on dead organic material and there’s plenty of that laying around at Ligaya Garden!
There you go, a brief overview of the life cycle of a mealworm. If you’re interested in breeding up your own for yourself or your pets, don’t forget to look at our other mealworm page about building a Mealworm Tower.