Phoenix Worms vs CalciWorms vs BSFL: Are They the Same Insect?
I've fed black soldier fly larvae for years, and I still get the same question almost weekly: "Are Phoenix Worms the same as CalciWorms? What about ReptiWorms and NutriGrubs?" The short answer is yes — every one of those names points to a single insect, Hermetia illucens, in its larval stage. Once you understand that, a lot of shopping confusion disappears and you can focus on the part that actually matters: how to use them.
The bottom line: one species, many brand names
Phoenix Worms, CalciWorms, ReptiWorms, NutriGrubs, and plain "BSFL" are all the larva of the black soldier fly. There is no nutritional or biological difference between them. You are buying the same animal regardless of which label is on the cup.
- Phoenix Worms — the original branded name, trademarked by Dr. Craig Sheppard, who did much of the early research that brought this larva into the reptile hobby.
- CalciWorms — a brand built around the high calcium content; common in the UK and Europe.
- ReptiWorms — branded specifically for the reptile market.
- NutriGrubs — another trade name emphasizing nutrition.
- BSFL / black soldier fly larvae — the generic, unbranded term most keepers and breeders now use.
All of them are the larval stage of Hermetia illucens, a beneficial fly native to the Americas. The adult looks a bit like a wasp but is completely harmless: it doesn't bite, sting, or even feed as an adult — it lives only to mate and lay eggs.
Why are there so many names?
This is a marketing and trademark story, not a biology one. When BSFL first reached the pet trade, different companies wanted distinctive, ownable names so their cups would stand out on a shelf. "Phoenix Worms" got there first and became almost a generic term, the way people say "Kleenex" for tissues. Competitors couldn't legally use that trademark, so they coined their own — CalciWorms, ReptiWorms, NutriGrubs — for the identical insect.
The result is a market where five names compete to sell one larva. The practical takeaway: don't pay a brand premium expecting a better bug. Once you know they're the same, you can buy on price, size, and shipping freshness instead of the label.
The nutrition (identical across every brand name)
Here are the figures that matter for a feeder. These are typical published values for Hermetia illucens larvae; exact numbers shift a little with diet and larval age, but the profile is consistent.
| Nutrient | Typical value |
|---|---|
| Protein | ~17% |
| Fat | ~14% |
| Moisture | ~61% |
| Calcium | ~9,340 mg/kg |
| Ca:P ratio | ~6.9 : 1 |
| Calcium dusting required? | No |
The headline number is calcium. Most feeder insects are phosphorus-heavy — crickets sit near a 1:9 Ca:P ratio, mealworms even worse — which is exactly why keepers dust them with calcium powder before feeding. BSFL are the standout exception. Their calcium is genuinely surplus relative to phosphorus, so they're the one common feeder you can offer without dusting and still come out calcium-positive.
That doesn't make BSFL a complete diet by themselves. The protein and fat numbers are moderate, and a larva that barely moves in a dish won't trigger a strong feeding response in every reptile. Their job is to lift the calcium balance of the overall rotation.
A note on the calcium myth that goes the other way
Because BSFL are calcium-rich, some keepers assume the calcium is "locked" in the cuticle and unavailable. Published feeding studies don't support that — the calcium in BSFL is biologically meaningful, which is a big part of why they reduce the dusting load when worked into a rotation. The Merck Veterinary Manual's guidance on metabolic bone disease (MBD) underlines why this matters: chronic calcium deficiency relative to phosphorus is one of the most common nutritional diseases in captive reptiles, and a calcium-positive feeder helps close that gap.
How to use BSFL (by any name)
Treat them as a calcium-boosting supplement and variety feeder, 1–3 times per week, alongside your primary feeders. A practical rotation looks like this:
- Protein staple: discoid roaches (the calorie-and-protein base of the diet)
- Low-fat supplement: silkworms (very lean, no dusting drama)
- Calcium boost: BSFL — no dusting needed
- Hydration treat: hornworms (very high moisture)
A few handling tips from keeping them myself:
- Storage. Hold them in the fridge at roughly 50–55°F. The cold slows their development so they stay in the feeder stage for about 2–3 weeks. They need no feeding or maintenance while stored.
- Don't freeze them. Below ~40°F they start dying off; the fridge door or a mid-shelf spot is usually safer than the back of a cold fridge.
- Warm before feeding. Cold larvae are sluggish. Let a portion sit at room temperature for a few minutes so they wiggle and catch your animal's eye.
- Watch for color change. As they age, larvae darken toward black and enter the pre-pupal stage. They're still safe to feed, but feeding response drops because they stop moving — use them before they turn if you can.
You can shop them at the BSFL / black soldier fly larvae collection — same premium larvae, no brand-name markup.
Frequently asked questions
Are Phoenix Worms the same as CalciWorms? Yes. Both are brand names for Hermetia illucens larvae. Identical insect, identical nutrition.
Why do BSFL sometimes look different between cups? Larval size and age vary by batch and how recently they were fed. That's a sizing difference, not a species or brand difference.
Do BSFL turn into something? Yes — left at room temperature they pupate and eventually emerge as black soldier flies. The adult fly is harmless and short-lived, but most keepers refrigerate the larvae and use them before that happens.
For where BSFL fit against a protein staple, see Phoenix Worms vs Dubia roaches, and for the full rotation see the ultimate guide to feeding reptiles.