A kilogram of Calci Worms contains roughly 9000 mg of calcium, that is 9 grams for every kilo. To put that into some sort of context Cows Milk contains 1220 mg of calcium per kilo thats 1.2 grams. A humans recommended daily intake of calcium is 1000mg (1g). So as an adult human we could drink a litre of milk or eat 100g of Calci Worms! (theoretically). This is just a fun example to show just how much calcium is in Calci Worms.
Now lets compare that to other Live foods commonly used for feeding reptiles, well all of them, Meal worms, crickets, roaches, wax worms, none of them come anywhere near, Meal worms come in at around 150 - 200mg of calcium per Kilo, that is 0.2 grams. Lets go back to our theoretical just for fun human analogy.. Your going to need to eat 5 kilos of meal worms to get your recommended daily allowance. Crickets come in slightly better at around 350mg per kilo (0.35 grams) so your only going to have to eat 3 kilos to get your daily limit
So as you can see calci worms absolutely blow all other live foods away in the calcium stakes, so much so they are the only live food to have a positive calcium to phosphorous ratio, that is they have more calcium than phosphorous in them. So in theory all we have to do is ditch all the other live foods, feed all of our reptiles nothing but calci worms and they will live happily ever after with big strong healthy bones right?
Well no unfortunately not, although calci worms have 50 times more calcium in them than the other live food options they come with two specific problems that prevent them from being the "one stop fits all" diet solution and why a varied diet still remains absolutely critical for reptile and amphibian health. First problem being they do not contain all of the required vitamins at sufficient levels for use as a sole diet, They can be gut loaded, but gut loading a calci worm is not as straight forward as gut loading a cricket. To gut load a cricket we just feed it a dry diet and fresh vegetables, it eats it, job done. To properly gut load a calci worm correct temperatures, diet and humidity need to be maintained.
Second problem, not all of that calcium makes it way into the animal. The Calci worm pulls off its amazing feat of calcium richness by having an exoskeleton of mineralised calcium. To put this in extremely basic terms its skin is made of calcium. Studies show that in species that do not sufficiently chew their food the calcium uptake is reduced owing to the digestive enzymes being unable to sufficiently break the skin down. Tests showed that in leopard geckos that around 40% of the available calcium was digested and the same in amphibians, however by crushing the calci worms in a pestle and mortar and then feeding to amphibians the calcium digested was up at around 80%.
So to summarise as simply as possible, the calcium in calci worms is locked up in their skin, if the animal scoffs them down without chewing their food, most of that calcium is likely to be pooped out the other end. This is particularly going to be an issue for amphibians and some of the smaller lizards that tend to swallow prey whole and not much so for the bigger jawed lizards that would take mouthful's at a time and crush them as they consume them.
Food for thought? despite their apparent super insect status on paper, calci worms do make an important element of a varied diet. But the diet still needs to be varied, gut loaded and where necessary supplemented with minerals and vitamins.
We have set out our understanding on this subject in the simplest terms possible, to fully get your nerd on we suggest you visit these two papers...
Boykin, Kimberly L., "Assessing the Nutritional Value of Black Soldier Fly Larvae (Hermetia illucens) Used for Reptile Foods" (2019). LSU Master's Theses. 4927. https://digitalcommons.lsu.edu/gradschool_theses/4927
Digestibility of black soldier fly larvae (Hermetia illucens) fed to leopard geckos (Eublepharis macularius)https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0232496