I was thinking of getting some of these in my next bug order, and did a little more digging. I was looking for phosphorus content and found an research paper in which the data disagrees with many of the nutritional claims except. In addition, the paper compares the detailed nutritional content for major nutrients, amino-acids and vitamins and made the conclusion that butterworms "are probably inappropriate as the bulk of an insectivore’s daily diet."
The same author did a similar study on the other common feeders (Crickets, Superworms, Mealworms, Silkworms and Waxworms, in addition to the one that has the Butterworms and Phoenix Worms) so its an interesting direct comparison. The common feeders like mealworms and crickets in the study line up with other published nutrition information. I wish I could get a copy of that one... "Complete nutrient composition of commercially raised invertebrates used as food for insectivores. Zoo Biol 21:286–293"
It's starting to seem suspicious to me and I'm a little worried the sellers of these bugs are being misleading, especially considering the marketing they are using looks almost exactly the same. One even claims "*The Calcium content is more than twice that of any other known feeder insect!" Any thoughts?
Complete Nutrient Content of Four Species of Feeder Insects by Mark D. Finke
Moisture : 60.2%
Ca (mg/100g) : 12.5 (Lowest of the 11 feeder insects)
P (mg/100g) : 225
Ca
: 0.06:1 (Typical with other feeders, except Phoenix worms)
Fat : 29.4 g/kg (Highest of the 11 feeders, including waxworms)
% Calories from Fat : 89% (Highest of the 11 feeders, including waxworms)
Protein (g/100g) : 15.5 (This one is close as well)
From Elliot's Butterworm/Mullberry Farms
Moisture 58.54
Ash 1.04
Protein 16.20
Fat 5.21
Calories/Fat 87.73
Calcium (ml/100 grs) 42.90*
* Exceptionally High Calcium
Edit: Added protein