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What Do Mealworms Eat? (With Pictures And Video)

If you don’t have much to do with mealworms, you’re probably wondering why someone would care what mealworms eat.

The truth is that mealworms are very useful little creatures, first of all for feeding pet animals, such as fish, birds, or small reptiles. They can also be used as bait for fishing.

Mealworms are very useful for research purposes (a non-model organism used in the proof of concept studies), and (surprise!), they are eatable for humans, for example in insect burgers.

If they are edible for humans, that must mean they are tasty, nutritious, and, most importantly, disease-free.

Mealworms can eat pretty much anything, so the fact that they are edible for humans is even more intriguing: what’s so special about the mealworms and their diet that makes them suitable for so many different consumers?

What Are Mealworms?

I said “insect” earlier because the mealworms are the larvae of the mealworm beetle (Tenebrio molitor), an insect with a complete metamorphosis process.

The larvae stage is the second (egg stage being the first), and the mealworms molt nine to twenty times before they reach the “pupa” level, and then the final stage of adult.

The larvae stage lasts eight to ten weeks, but what are the mealworms are feeding on at this stage?

What Do Mealworms Eat?

Cereals: Grains And Meals

The mealworms are not always welcome due to their appetite for cereal grains, as they can feed mercilessly on stored cereals like wheat, oat, barley, corn, and milo.

Moreover, as their name suggests, mealworms have no problem eating the same cereals but in other forms (ground or cooked).

Mealworms are considered pests not just for consuming stored grains, but sometimes even for infesting the stored ground grains (e.g. flour, corn, bran) or the food itself (bread, polenta, oatmeal, etc.).

However, for those who want to raise mealworms, that’s good news as it means one can easily find the necessary food to feed these valuable worms.

Mealworms do not drink water, so the consumed food must be moist enough to hydrate them; therefore, they will do better on soft-cooked grains or soaked meals.

Nuts And Seeds

Mealworms will also eat various nuts such as walnuts, pecans, almonds, and seeds like sunflower seeds, quinoa seeds, and even birds seeds. So it’s safe to feed them these along with other foods.

However, nuts and seeds should come more as supplements to more moist foods since they do not contain enough water to hydrate the mealworms, even though the fats and nutrients benefit the worms.

Fungi

Fungi are a great source of sustenance for mealworms as they are abundant in water and nutrients.

As long as fungi is not fed in excess, as it might make them sick, mealworms would eat almost any type of fungus: mushrooms, lichen, yeast, and even mold from food or plants.

So, you could feed their mealworms with moldy bread, for example, with no worries, as long as you make sure the worms also have an additional moisture source like fruits and veggies.

Fruits And Veggies

 

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It is essential to remain hydrated and, since they can not drink water, they must consume fruits and veggies to provide themselves with the necessary amount of moisture.

Mealworms growers offer fruits and vegetables along with dry food. Mealworms will eat pretty much any fruit or vegetable iavailable, including decayed ones; these are especially appreciated for the mold that grows on them.

Mealworms even have favorite fruits, such as apples, pears, grapes, peaches, strawberries, apricots, watermelon, or bananas, and favorite vegetables, such as carrots, pumpkins, beans, or leafy greens.

So that the mealworms can eat them easily, the fruits and vegetables are cut into tiny slices before being fed to the worms.[1]

However, there are some fruits and vegetables that mealworms do not seem to appreciate: citrus fruits and onions.

Decomposed Plants And Food

For mealworms living in the wild, decomposed plants are the primary source of nourishment, also offering them, a safe habitat beneath the layer of rotting vegetation.

The moisture of decomposing plants is an excellent source of hydration, and mealworms spoil themselves with some tasty mold as a bonus.

Mealworms do not have preferences about which plants or which plant parts they would eat; as long as the plant material is juicy and moldy, the mealworms would gladly consume them.

For home-grown mealworms, feeding them leftovers of fruits and vegetables (even peels in some cases, such as bananas) can be the perfect meal.

Pets Food

Well, you can feed the pet food to the mealworms, or they can invade it and eat it themselves; either way, the point is that mealworms will eat pet food, cats’ or dogs’ food alike.

Mealworms are omnivorous, so eating pet food doesn’t harm them and them a protein boost considering how nutrient-rich the pellets are.

Before feeding them to mealworms, pet food pellets must be smashed; a fruit or a vegetable slice should accompany the ground pet food to fulfil the mealworm’s need for moisture.

People who have fed their mealworms with pet food pellets have noticed a preference for chicken flavored pet food.

Considering all the information so far, does that mean mealworms will eat meat too?

Do Mealworms Eat Meat?

Meat is not the first choice for a mealworm. However, in challenging situations of limited food sources, they would eat other insects’ larvae (e.g. hornworms) or worms (e.g. earthworms).

Mealworms can eat animal matter in small quantities. Therefore, it is possible to find them from time to time  on dead, decaying animals.

Moreover, the mealworms will resort to cannibalism if they do not have enough food or even if they do not have enough moisture.

What Else Can Mealworms Eat?

What Else Can Mealworms Eat

Credit: @styrostylez

Inside a mealworms’ digestive tract some microorganisms have been found which decompound polymeric synthetic materials, such as polystyrene and plastic.

Plastic (polyethylene) and polystyrene are toxic because of HBCD – hexabromocyclododecane, a resilient and bioaccumulative flame-retardant chemical.

Mealworms can actually live on a full-time diet made out of these synthetics!

The chemical compounds pass through the worms’ digestive tract just like any other food, except that they are eaten and processed much more slowly than plant-based foods.

Of course, mealworms that eat plastic or polystyrene don’t manifest any sign of illness or other disturbances compared to the mealworms that feed on a plant-based diet.

The mealworms that feed on plastic and polystyrene also eliminate the emission of carbon dioxide emitted from feces, like those feeding on plants.

Researchers suggest that these feces are just as suitable as soil fertilizer as the feces of mealworms fed with plants!

Moreover, no toxins have been found within the mealworms, even after a long period of feeding the worms exclusively with synthetic materials. The fact that they do not retain any toxins makes them edible to other animals (e.g. lizards, birds, fish).

According to the studies, a hundred mealworms can eat between 34 and 39 milligrams of polystyrene or styrofoam per day and eliminate it within twenty-four hours. They emit half  the carbon dioxide and half the amount of non-toxic feces compared to mealworms fed on other foods.[2]

Of course, there are still ongoing studies aimed at ensuring there are no adverse effects in the long term for the subsequent generations of the mealworms fed with synthetic materials.

Perhaps by this point you have started wondering why we don’t clean the planet and waters of all the plastic waste they are choked with? Well, it might be a bit more complicated than it seems.[3]

What Do Mealworms’ Spawn Eat?

The spawn of mealworms do not have a very different diet from their older siblings, except that they require more moisture in their food.

There are nine to twenty larval stages, and with each stage, the mealworms’ jaws get tougher until they can eat food like grains, bark, or even plastic.

In the wild, mealworm spawns in the first larvae stages feed on fungi, decomposing plant matter and, later on, seeds.

Home-raised mealworm spawns feed on juicy slices of all sorts of fruits and veggies, from bananas (with peel) and peaches to carrots and potatoes.

Of course, home-raised mealworms would gladly eat a meal with added moisture, such as oatmeal or branmeal, and can switch to pet food later, when their jaws are strong enough.

How Much Do Mealworms Eat?

The mealworms eat everything available to them, both in the wild and in domestic settings.

Shedding the exoskeleton multiple times during the larval stage allows mealworms to get bigger and bigger with every molt.

Therefore, mealworms can eat as much as they please if they find food – they grow bigger and bigger from one stage to another, becoming a larger adult beetle, thus with more chances to survive.

In home-raising, mealworms are fed plenty and often, they grow faster, and the worms are fatter and juicier. The period of not feeding the mealworms fresh material or changing the decayed matter is one or two weeks (maximum).

What Should Mealworms Not Eat?

As you have seen so far, there is nothing out there that mealworms cannot eat, even though some tough materials require a longer period between consumption.

Nonetheless, some things could harm mealworms in certain circumstances, or others could even be toxic:

  • Water: not only can mealworms not drink it, but it can be dangerous for them if in excess, or even if the habitat is too moist – the worms could drown.
  • Dry food only: this wouldn’t fulfil the mealworms’ need for moisture, and they can die from dehydration.
  • Other chemical compounds, like poisons and gasoline, are toxic for the mealworms and the worms die if they feed on them.
  • Oil: it can drown mealworms and poison them.[4]

Conclusions

Mealworms can eat pretty much anything,  with the condition to maintain a balance between the dry foods and the moist ones.

Mealworms cannot drink water, so they need wet nourishment to maintain hydration.

In the wild, mealworms feed on fungus, bark, seeds, and in desperate circumstances they would eat other dead worms or decaying animal flesh.

In home-raising, mealworms feed mainly on slices of fresh fruits and vegetables, cereal meals, cereal grains, decaying plant matter, and even cats’ and dogs’ food.

Mealworms’ spawn have about the same diet as their older siblings, except they need more moisture. Therefore, the baby mealworms feed on juicy slices of fresh vegetables and fruits in the first larval stages.

Mealworms have certain digestive microorganisms that allow them to consume polystyrene and polyethylene (plastic) without being harmed by the toxic chemicals they contain (HBCD).

Moreover, mealworms do not retain the toxins of the synthetic materials in their bodies. The HBCD is simply decomposed in the mealworms’ digestive tract, and the worms emit less carbon dioxide and non-toxic feces.

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