One of the most common questions we get from new keepers is also one of the simplest: “Wait, how often am I supposed to feed this thing?” Invertebrates are wonderfully low-maintenance eaters, but the right amount and the right feeder genuinely vary from a 2mm spiderling to a roly-poly colony to a praying mantis. So we built the chart we wish we’d had when we started — a quick, scannable reference for who eats what, how often, and how much. Bookmark it, screenshot it, tape it to the shelf above your enclosures.
Quick answer: Most pet invertebrates eat live feeders (crickets, flightless fruit flies, roaches) on a schedule that depends on age — babies eat small and often (every 1–3 days), adults eat larger and rarely (every 5–7 days, sometimes monthly for big tarantulas). Detritivores like isopods graze constantly on leaf litter with occasional protein. The golden rule across the board: prey should be no bigger than your pet’s abdomen, and you should always have clean water available. Use the chart below as your starting point, then read your pet’s abdomen and adjust.
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The Invertebrate Feeding Chart
These are starting points based on keeper-community consensus. Always adjust to your individual pet’s body condition (more on that below).
| Pet | What they eat | How often | Portion & notes |
|---|---|---|---|
| Jumping spider (spiderling) | Flightless fruit flies (D. melanogaster), pinhead crickets | Every 1–2 days | 1–2 prey items; keep food slightly smaller than the abdomen |
| Jumping spider (juvenile) | Larger fruit flies (D. hydei), small crickets, bottle flies | Every 2–3 days | 1–2 items; stop when the abdomen looks plump |
| Jumping spider (adult) | Small crickets, bottle flies, the occasional mealworm or waxworm | Every 3–7 days | 1–2 items, roughly 1–2x/week |
| Tarantula (sling) | Pre-killed or small crickets, flightless fruit flies | 2–3 times a week | Prey no bigger than the abdomen; slings are fragile, keep them fed |
| Tarantula (juvenile/adult) | Crickets, dubia roaches, the occasional larger feeder | Weekly to monthly | A few crickets; big adults may eat just 4–5 crickets a month |
| Praying mantis (nymph) | Flightless fruit flies, micro-crickets, aphids | Every 2–3 days | 5–10 fruit flies; feed when the abdomen isn’t full |
| Praying mantis (adult) | Crickets, blue/green bottle flies, roaches | Every 2–4 days | Prey up to about half the mantis’s size |
| Isopods (roly-polies) | Leaf litter, decaying wood, fungi + protein (fish flake, dried shrimp) | Always available; protein 1–2x/week | Provide constant leaf litter; add a calcium source like cuttlebone |
| Millipedes | Decaying leaves and wood, soft fruit, prepared “bug grub” | Always available | Mostly detritivores; supplement calcium for the exoskeleton |
| Springtails (cleanup crew) | Mold, fungi, decaying matter; rice/yeast in cultures | Self-sustaining | Basically feed themselves in a bioactive setup |
| Moth/butterfly caterpillars | Fresh host-plant leaves (species-specific) | Daily, fresh | Match the plant to the species; never use sprayed leaves |
New to a particular critter? Our deeper guides go species-by-species — start with the Invertebrates Care Hub, or jump to what jumping spiders eat and our isopod setup guide.
The Golden Rule: Prey Size
If you remember one thing, make it this: a feeder should be no larger than your pet’s abdomen (for spiders) or about half its body length (for mantises). Oversized prey is genuinely dangerous — a too-big cricket can injure or even kill a small spider, and the stress of wrestling huge prey isn’t worth it. When in doubt, size down. A pet that eats two small crickets is happier and safer than one fighting a giant.
The everyday staple: small crickets are the workhorse feeder for most pet inverts — easy to gut-load, the right size for juveniles and adults, and widely accepted by spiders and mantises alike.
Read the Abdomen, Not the Calendar
A feeding chart is a starting point, not a law. The real gauge is your pet’s body. For spiders, watch the abdomen (the rounded rear segment):
- Plump and rounded — perfect. You’re feeding the right amount.
- Shrunken or wrinkled — feed more often, and check hydration.
- Tight and shiny, very large — ease off; an over-full abdomen is easy to injure and may signal pre-molt.
And remember: a pet that suddenly refuses food usually isn’t sick — it’s often heading into a molt. Before you worry, check our molting guide and our invertebrate health guide to tell the difference.
Gut-Loading & Supplements
Here’s a detail that quietly makes a big difference: your pet is what its feeders ate. A cricket that’s been living on cardboard is a nutritionally empty meal. Gut-loading — feeding your feeders fresh veg, leafy greens, and a quality grain-based food for 24–48 hours before offering them — passes that nutrition straight to your pet. It’s the highest-value, lowest-effort upgrade you can make to feeding day.
Insects are naturally low in calcium (their shells are chitin, not calcium), so some keepers lightly dust feeders with a calcium supplement, especially for growing animals. For detritivores like isopods and millipedes, a piece of cuttlebone or other calcium source in the enclosure does the same job and helps them build strong new exoskeletons after each molt.
Add variety: rotating in mealworms gives larger juveniles and adults a change of pace and a protein boost — handy to keep on hand alongside your main feeders.
Know Your Feeders
- Flightless fruit flies — the backbone for tiny mouths. Drosophila melanogaster for the smallest spiderlings and mantis nymphs; the larger D. hydei for bigger juveniles.
- Crickets — the all-purpose staple. Pinheads for babies, small crickets for juveniles and adults. Easy to gut-load.
- Bottle flies (blue/green) — hatched from “spikes,” a favorite of jumping spiders and a great clean feeder.
- Dubia roaches — meaty, slow, and easy to keep; popular for larger tarantulas and mantises.
- Mealworms — fine as an occasional item; the hard shell makes them a sometimes-food, not a staple.
- Waxworms — the candy of the feeder world. Rich and fatty, so save them as a treat, not a meal plan.
An occasional treat: waxworms are rich and fatty — perfect as a once-in-a-while pick-me-up for an adult that needs to put on a little weight (just don’t overdo it).
Don’t Forget Water
Food gets all the attention, but water is the bigger deal. Dehydration is the leading cause of death across the hobby, so every enclosure should have clean water — a shallow dish, water-bead gel, or regular light misting, depending on the species. A well-fed but dehydrated invertebrate is still in trouble.
A Word on Overfeeding
It’s tempting to feed constantly — they’re so fun to watch hunt! — but “power-feeding” a spider to grow it fast can leave the abdomen dangerously oversized and prone to rupture. Slow and steady wins. Stick to the chart, read the abdomen, always remove uneaten prey (a leftover cricket can harass a molting pet), and you’ll rarely go wrong.
Frequently Asked Questions
How often should I feed my jumping spider?
It depends on age: spiderlings every 1–2 days, juveniles every 2–3 days, and adults every 3–7 days (about once or twice a week). Let the abdomen be your guide — plump means you’re on track.
What size prey is safe?
As a rule, no larger than your pet’s abdomen for spiders, or about half the body length for mantises. When unsure, choose the smaller feeder.
My pet stopped eating — should I worry?
Usually not. Food refusal is most often a sign of an approaching molt, not illness. Keep water available and hold off on feeding; see our molting and health guides to tell the difference.
Do I really need to gut-load feeders?
It’s one of the easiest ways to improve your pet’s nutrition. Feeders raised on fresh produce and quality food for a day or two before feeding pass that goodness straight to your pet.
Explore Related Guides
- The Invertebrates Care Hub — start here
- Can Jumping Spiders Eat Mealworms?
- Invertebrate Molting Guide
- Invertebrate Health & Signs of Illness
Be good. Do the research. Love your weirdo.