Mealworms with Carrot

If you have a reptile or amphibian, you may be feeding live insects. These insects serve as pet food; however, the contents of the insect decide how healthy a meal it is. Gut-loading mealworms ensures that you’re feeding your pet nutrient-dense food that can help avoid malnutrition-related problems. Because of gut loading, practically any nutrient may be used as long as the meal is pleasant to the insect and contains adequate amounts of the target nutrient(s)

What are Mealworms?

The darkling beetle, Tenebrio Molitor, produces mealworms as larvae. The darkling beetle is a holometabolous insect with four phases of development: egg, larva, pupa, and adult. The mealworm is a darkling beetle that lives as a larva for 90 to 114 days before becoming a pupa. Mealworms hatch from white bean-shaped eggs about 1/20 inch (1.27 mm) in length. The larvae are white when they are initially hatched, but they will change to honey-yellow or yellow-brown after a few days. The mealworm will be 1.25 inches (3.18 cm) long when fully grown. Their bodies are sleek and firm, and they have a gleaming finish.

Nutritional Value of Adult Mealworms

  • 61.9 percent moisture
  • 18.7 percent protein
  • 13.4 percent fat
  • 0.9 percent ash
  • 2.5 percent fiber
  • 169 mg/kg calcium
  • 2950 mg/kg phosphorus

What is Gut-Loading?

The term “gut loading” refers to feeding a particular diet to insects just before they are eaten. When the insect consumes this meal, which has high quantities of the targeted nutrient(s), it will remain in the insect’s stomach, hence boosting the insectivore’s nutritional intake. Gut loading focuses on calcium supplementation, and studies have been conducted to determine the duration between loading the gut and providing food for your pet. It varies depending on the gut load and insect.

Most studies on gut loading outcomes in insects have improved calcium content. House crickets, yellow-mealworm larvae, silkworm larvae, and wax-moth larvae have shown that diets with increased calcium provide 5–10% calcium, often from calcium carbonate, which is beneficial in boosting calcium content.

How Fast Do Mealworms Grow?

Mealworms grow reasonably fast and will hatch from an egg and grow through until it is ready to pupate in 3 months.

Mealworm Growth Timeline

  • A few days after emerging from its cocoon, a Darkling beetle achieves adulthood. A female can lay hundreds, if not thousands, of eggs throughout her 3-month existence.
  • It takes between 4 and 19 days for the egg to hatch (often around 12 days).
  • It hatches as a tiny, pale larva that is difficult to spot at first.
  • As the larva matures, it will go through multiple larval stages (up to 20) and lose its exoskeleton. It will be golden brown and between 1″ and 1.4″ long after its last molt, which occurs around 3 months after it has emerged from an egg.
  • If the mealworm is not harvested at this point, it will pupate, encasing itself in a cream, hard shell that does not move or eat.
  • A beetle will emerge after 6-18 days. It will start pale brown and feeble, but it will darken into a black, lustrous beetle in a few days, and the cycle may begin again.

More for You: How to Breed Hornworms

What Eats Mealworms?

Mealworms are a terrific way to supplement the feed of both wild and pet reptiles. Common reptiles that eat mealworms are the Bearded dragon, Leopard gecko, Crested gecko, Veiled chameleon, Blue-Tongue Skink, and Green Basilisk. Also, because they have a higher calorific content than crickets, another typical reptile feeder, they’re also a special treat for different species, including birds, amphibians, and fish. However, it is essential to remember that they are only a supplement. Mealworms naturally have low calcium and aren’t nutritious enough to replace a reptile’s whole diet.

How to Gut Load Mealworms?

You can buy specific gut loading mealworm chow or use fresh leafy greens and veggies and feed them to your mealworms. All you need to do is simply add these to the mealworms’ box or container and let them feed. Vitamin D is also required as part of the gut-loading process and this can be achieved either by using a vitamin D supplement with the gut loading foods, or recent studies have shown that mealworms become naturally high in vitamin D when exposed to UVB light up to 48 hours in advance of feeding.

How Long Before Feeding Should You Gut Load Mealworms?

It is ideal to perform gut loading within 1 to 3 days prior to giving the prey to the pet to ensure your pet gets maximum nutrition. Furthermore, giving a variety of insects to your pet is beneficial. Therefore, you must also gut load, mealworms, crickets, super worms, and other insects for your pet.

What Foods Are Best to Gut Load Mealworms?

Mealworms aren’t fussy eaters, but some foods are healthier for them to consume because anything you feed your mealworms will ultimately end up in your pet. You may either utilize a high-quality commercial mealworm gut load mix (amazon link – opens in a new tab) or feed a consistent supply of healthy, nontoxic veggies such as squash, sweet potatoes, and dark leafy greens. A proper gut load can also include calcium-fortified fish flakes, fruits, vegetables, cereals, or chicken feed. You may also feed them dried foods like bran bread, cat food, or other dry food. Furthermore, mealworms have a cannibalism tendency and readily consume dead or injured congeners.

Note: Avoid giving avocados, onions, citrus, and other vegetables known to be harmful to reptiles.


As you can see, gut-loading mealworms is a straightforward task. It just involves feeding your insects nutritious foods that will also be beneficial to your pet. Just add the foods to your insect-holding enclosure and let them have a feast for around 1-3 days before feeding them to your hungry little friend. Remember, mealworms can also be great at producing vitamin D so if you are able to expose them to some UVB light too, that will make them even more of a healthy meal.

How to Gut-load mealworms Infographic

Reptile Wrestler Tips!

“Do not feed your prey insects with anything that could ultimately be harmful to your pet!”

“Sprinkle calcium powders over the gut loading veggies before feeding them to the mealworms!”

“Expose your mealworms to UVB light 48 hours prior to feeding to make them a rich source of vitamin D!”

“Mealworms purchased from pet stores are extremely unlikely to have been properly gut-loaded and will have little added nutritional value!”


What are mealworms used for?

Mealworms are mainly used as food for reptiles and birds and as fishing bait. Mealworms are abundant in protein, making them a popular choice among reptile and bird owners.

Can mealworms bite?

No, mealworms cannot bite. Mealworms are a type of beetle larva that is found in the wild and is used as food for pets and other animals. They are not able to bite humans or your pet.

Do mealworms shed?

Mealworms go through a process of molting or shedding their skin, many times as they grow. The old skin is shed in one piece and the mealworm wiggles their way out of it. Mealworms can molt up to 20 times!

Is there a lizard that eats only mealworms?

No, there is no lizard that only eats mealworms. Mealworms are not a very nutritious food source, so lizards would not be able to survive on them as their sole diet. However, if mealworms are gut loaded (fed a diet high in nutrients), they can be a staple food source for lizards.

About Me

Hi, I’m Stuart and I’ve had reptiles for as long as I can remember. When I was younger, I studied for a master’s in Herpetology. Over the years I have worked at several zoos before opening my very own reptile sanctuary. In my spare time, I run this website – which is a resource for people who want to learn more about their little beasties.

RW Face

More You Might Like