Mealworms are the larval form of the mealworm beetle, Tenebrio molitor, a species of darkling beetle. Like all holometabolic insects, they go through four life stages: egg, larva, pupa, and adult.

Larvae typically measure about 2.5 cm or more, whereas adults are generally between 1.25 and 1.8 cm in length.

Mealworms are the larval form of the mealworm beetle, Tenebrio molitor, a species of darkling beetle. Like all holometabolic insects, they go through four life stages: egg, larva, pupa, and adult.

Mealworms are typically used as a pet food for captive reptiles, fish, and birds. They are also provided to wild birds in bird feeders, particularly during the nesting season.

Mealworms are useful for their high protein content. They are also used as fishing bait.

Larvae typically measure about 2.5 cm or more, whereas adults are generally between 1.25 and 1.8 cm in length. (source)

So can guinea pigs eat mealworms?

They are not a food that should be purposely be fed to guinea pigs. They hold no nutritional value for them.