When your mantis, chameleon or lizard has outgrown fruit flies, blue bottle flies are the next size up, and spikes are how you get them. “Spikes” is the feeder-world name for the pupae of the blue bottle fly, Calliphora vomitoria: small, hard, reddish-brown capsules that look like grains of rice. They aren’t maggots and they aren’t flies yet. Keep them warm and big blue bottle flies (12–15 mm) chew their way out in a few days; keep them cold and they wait.
That’s what makes them easy. Pupae don’t eat and don’t need care, so you hatch flies on your own schedule instead of racing a live culture. The full method is in the hatch guide.
Who They’re For
Blue bottles are the bigger of the two bottle flies we sell:
- L6+ and adult mantises: Ghost, Spiny Flower, Orchid, Dead Leaf, African Twig, Double Shield at their largest stages. Flying-prey specialists like Spiny Flower and Orchid hunt them hard.
- Chameleons and other reptiles that ignore anything that isn’t airborne.
- Larger reptiles and amphibians that can handle a big fly.
If your animal is still small, these flies are too big. Start with D. melanogaster or D. hydei fruit flies, step up to green bottle spikes at L5–L6, and finish here from L6.
How to Hatch and Feed Them
Put the spikes you want to hatch in a ventilated cup (pinholes or a mesh lid, never sealed) somewhere 70–80 °F. No food, water or bedding: pupae don’t eat. Flies usually emerge in 2 to 7 days, faster when warm, slower when cool, and they stall below about 65 °F.
Unlike fruit flies, bottle flies can fly. Keep the lid on once they emerge. Before feeding, chill the cup in the fridge for 5–10 minutes; the flies go sluggish, so they’re easy to tip into the enclosure and easy for your animal to catch. A couple of flies every few days is plenty for a big mantis. A dab of honey or sugar water in the fly cup keeps the adults lively for the week or two they last.
For reptiles and frogs, follow your species’ own supplement schedule; mantises don’t need dusting.
Storage & Shelf Life
Not ready for flies yet? Refrigerate the spikes at about 40 °F (the crisper drawer is ideal). Cold slows a pupa almost to a stop. Plan on about a week, sometimes closer to two, and use them while they’re fresh, since fewer hatch the longer they sit. Never freeze them: the freezer kills pupae. Pull out what you want to hatch and put the rest back in the cold.
Frequently Asked Questions
What are blue bottle spikes?
Blue bottle spikes are the live pupae of the blue bottle fly, Calliphora vomitoria. They look like hard, reddish-brown grains of rice and hatch into large (12–15 mm) flies at room temperature, a feeder for L6+ and adult mantises, chameleons and larger reptiles.
How big are blue bottle flies compared to green bottle flies?
Blue bottles are the larger of the two at 12–15 mm. Green bottle spikes (Lucilia sericata) hatch into a slightly smaller fly, 8–10 mm, the first step up from fruit flies for L5–L6 mantises and smaller reptiles.
How do I keep spikes from hatching too soon?
Refrigerate them at about 40 °F. Cold pauses their development for about a week, sometimes closer to two. Never freeze them. At room temperature (70–80 °F) they hatch in 2 to 7 days.
Can mantises eat blue bottle flies?
Yes, mantises from about L6 onward, and adults, take blue bottle flies. They’re too large for younger nymphs: fruit flies through L4, green bottle flies at L5–L6, blue bottles from L6. See our feeding guide for stage-by-stage prey sizing.
