^^ where did you get the chart from if I may ask? If you do a Google search for "feeder insect chart" and go to images, there are many many different charts to look at and compare, including the one you posted here. Here's the Google search:
https://www.google.com/search?q=fee...PcDBoQ_AUIBigB#tbm=isch&q=feeder+insect+chart
The thing with these charts is, none of them are usually ever identical unless they are copycat charts from other charts. In the chart you shared, it's showing that butterworms only have a 5.21% fat content, a lot lower than superworms, crickets, and roaches..... and that it also has the highest calcium content of any feeder at 42.90% ....... but this cannot be true because a butterworm is mostly fat, whereas superworms, crickets, and roaches are composed of a lot less fat and more chitin and hard parts. Also, showing that a butterworm has a higher calcium content of 42.90% than a phoenix worm at 9.5% cannot be true as well, because phoenix worms / black soldier flies and their larvae, are PROVEN to have one of the HIGHEST calcium contents of any feeders that are available.
There are just so many different charts out there that the information is a bit conflicting in all of them. So which one do you follow then?
This specific chart here shows completely different information than the one posted above, but I believe it seems to be more in par with what is scientifically known to be fact regarding some of the feeders:
http://www.geckotime.com/wp-content/uploads/2014/04/table-large.png
With that ^^ chart, Phoenix worms are the ONLY ones on the entire list where the calcium content is significantly higher than the phosphorous content, and this is the reason that you never have to dust your phoenix worms or black soldier flies with calcium dust while you have to do it with the rest of your insects to even out the calcium-to-phosphorous ratio.
Now, I'm not saying that
this chart is 100% accurate, as I truly believe that there is no chart out there that is 100% accurate..... but I do believe that it is more correct than the one shared by "Rorschach" based on what I know to be true information regarding the phoenix worms in various studies done on them as nutritional feeders.
There needs to be a new study done on the comparisons and a new, updated, completely accurate chart needs to be made somehow. If you do that same
Google search and start going through the sites that pop up at the top of the list, you can find a lot more charts that won't even show up when you click IMAGES after your search. This is what I mean about so many conflicting charts. And most charts don't list all the insects available to us reptile keepers, just some.
I'm not 100% sure which chart from which site is the most accurate..... When I was doing my own research quite a while ago, I compared all of the charts I found and made a best guess based on the info I found to be most consistent within all the charts I viewed.
I wish this was a part of the RESOURCES section of this site so that way we can all have quick access to valuable, true information. I'ma cross my fingers and hope a new study is done one day and that info is added to the site here.