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Black Soldier Fly Larvae vs Mealworms for Chickens

The short answer

Black soldier fly larvae are the better treat for laying hens, because they carry meaningfully more calcium and a calcium-to-phosphorus ratio that supports shell building, while a mealworm's ratio runs the wrong way. Mealworms win on protein, 50.4% dried per Feedipedia against roughly 41% for dried BSFL per the INRAE feed tables, and most flocks find them more palatable. Both are treats, not feed, so either stays under the 10% treat limit Texas A&M's veterinary college puts on a chicken's diet. This comparison is built on cited INRAE and Feedipedia feed-table data rather than bag copy, and the numbers below are attributed line by line.

Updated · every claim sourced below

The numbers, from feed tables instead of bag copy

Dried BSFL run roughly 41% protein and 35% fat on a dry-matter basis, per the INRAE feed tables at feedtables.com and a 2022 peer-reviewed review. Dried mealworms run 50.4% protein, 35.6% fat, 0.24% calcium, and 0.77% phosphorus, per Feedipedia. BSFL calcium is genuinely variable, so we report it as the published range rather than pretending one number exists. The calcium-to-phosphorus ratios in the last row are computed by us from those same feed-table figures, not taken from any brand.

Nutrient (dried, dry-matter basis)Black soldier fly larvaeMealwormsSource
Protein~41%50.4%INRAE feed tables, PMC review; Feedipedia
Fat~35%35.6%INRAE feed tables, PMC review; Feedipedia
Calcium0.12 to 3.57% (published range)0.24%PMC review; Feedipedia
Phosphorus0.10 to 1.03% (published range)0.77%PMC review; Feedipedia
Ca:P ratio (computed by us)~4.6:1~1:3.2Computed from INRAE feed-table and Feedipedia figures

Why the calcium-to-phosphorus ratio decides it for laying hens

The ratio is the verdict engine, and we computed it ourselves from the feed tables because no brand publishes one. From the INRAE feed-table figures, dried BSFL work out to roughly 4.6 parts calcium to 1 part phosphorus. From Feedipedia's figures, dried mealworms work out to roughly 1 part calcium to 3.2 parts phosphorus. That mealworm ratio is inverted: the treat delivers more phosphorus than calcium. A laying hen is building an eggshell most days, and shell building needs calcium, so a treat that tips the diet toward phosphorus works against the one job her body is trying to do. BSFL push in the direction a layer needs. Mealworms push the other way. Neither replaces oyster shell or a complete layer feed, but if the flock is in lay and you are choosing one grub bag, this is the reason to choose BSFL.

BSFL calcium is a range, not a number

Nobody can honestly tell you the calcium content of dried BSFL as a single figure. The peer-reviewed literature spans 0.12% to 3.57% on a dry-matter basis, per the 2022 PMC review, and Grubbly's own guaranteed analysis states 1.0 to 1.5%. That spread is real, not sloppy measurement: what the larvae are reared on changes what ends up in them, so different producers and different studies land in different places. Any page quoting one clean BSFL calcium number has picked one point from that range. Even at the bottom of the range BSFL sit near a mealworm's 0.24% (Feedipedia), and at the top they carry many times more, which is why the ratio argument in the previous section holds across the range while any single multiplier does not.

The "50x more calcium" claim, checked

The brands do not agree with each other. Grubbly claims BSFL carry "50x more calcium than mealworms", GrubTerra and Mile Four both claim 75x, and FLYGRUBS claims 85x. Those three multipliers cannot all be right, and the independent feed tables support something smaller still: dividing the INRAE feed-table calcium figure for dried BSFL by Feedipedia's 0.24% for dried mealworms gives roughly 14x on a dry-matter basis. None of the brands shows its arithmetic, so we cannot say which figures sit behind which multiplier. What the published data gives you: BSFL calcium spans 0.12% to 3.57% in the literature, dried mealworms sit at 0.24%, and the feed-table averages work out to roughly 14x. Every version of the claim points the same direction, BSFL carry more calcium, but the size of the gap is nowhere near as settled as the bags suggest.

Where mealworms win: protein and palatability

Mealworms are the higher-protein treat, 50.4% dried per Feedipedia against roughly 41% for dried BSFL per the INRAE feed tables, and that gap matters most during molt, when hens are rebuilding feathers that are mostly protein. They are also the safer bet for a picky flock: chickens that shrug at BSFL will usually mob a handful of mealworms, which makes them the better training treat for getting birds back in the run or into the coop at dusk. Fat is a wash, 35.6% against roughly 35%, so neither is the lean option. If your hens are molting rather than laying, or you mainly want a treat they will reliably chase, mealworms are the right pick, and the calcium argument matters less because there is no shell being built during a molt.

What keepers actually see: palatability varies by flock

Buy a small bag first, whichever grub you choose, because real flocks do not read feed tables. On BackYard Chickens, keeper FrostRanger reports "Some birds just don't like bsfl", and Appalachickens writes "I bought a big box of bsf larvae and my girls are completely uninterested." The opposite happens too: Indianahens2 says "My chickens go crazy over Flygrubbs, the brand." All three are describing the same product category, and all three are right about their own birds. Palatability varies flock to flock and bird to bird, so the nutrition argument only matters if your chickens will actually eat the things. Start with the smallest bag a brand sells, confirm your flock's verdict, then size up. When you are ready to pick a bag, our ranked grub treats compares the US brands on published analysis, origin, and price per pound. And keep any treat, grubs or mealworms, less than 10% of the daily diet, the limit Texas A&M's veterinary college puts on chicken treats.

Quick answers

Are black soldier fly larvae or mealworms better for laying hens?

Black soldier fly larvae. Their calcium-to-phosphorus ratio, roughly 4.6:1 computed from the INRAE feed tables, supports shell building, while dried mealworms run roughly 1:3.2 the other way per Feedipedia's figures, delivering more phosphorus than calcium. For a hen in lay, that ratio outweighs the mealworm's protein edge.

Are mealworms higher in protein than BSFL?

Yes. Dried mealworms run 50.4% protein per Feedipedia, against roughly 41% for dried BSFL per the INRAE feed tables, both on a dry-matter basis. That makes mealworms the stronger pick during molt, when hens are rebuilding feathers.

How much of either can I feed my chickens?

Treats should stay less than 10% of the daily diet, per Texas A&M's School of Veterinary Medicine, and that covers grubs and mealworms alike. The other 90% or more should be a complete feed, which carries the vitamins and minerals neither treat does.

Is the "50x more calcium than mealworms" claim true?

It is one of three competing brand numbers: Grubbly says 50x, GrubTerra and Mile Four say 75x, FLYGRUBS says 85x. The INRAE and Feedipedia feed tables support roughly 14x on a dry-matter basis. BSFL do carry more calcium; the exact multiple is not settled.

How much calcium do black soldier fly larvae actually contain?

There is no single honest number. The peer-reviewed literature reports 0.12% to 3.57% on a dry-matter basis, and Grubbly's own guaranteed analysis states 1.0 to 1.5%. The variation is real, driven largely by what the larvae are reared on, so treat any single-figure claim as one point picked from that range.

Why won't my chickens eat black soldier fly larvae?

Some birds simply do not like them, and keepers on BackYard Chickens report whole flocks ignoring BSFL while other flocks devour them. Palatability varies bird to bird. Try mixing a few into a treat they already love, and buy the smallest bag first so an uninterested flock costs you little.

Sources