Feeding pet invertebrates isn’t complicated once you understand the basic logic: match the food to the species, and feed less often than you’d think. Overfeeding — not underfeeding — is the more common mistake.
What Do Pet Invertebrates Eat?
It splits cleanly by group. Tarantulas and scorpions are predators — they eat live prey like crickets, roaches, or mealworms, sized to roughly the width of the animal’s body. Isopods and millipedes are detritivores — they eat decaying leaf litter, wood, and vegetable scraps, and do best with a steady supply rather than scheduled “meals.” Stick insects are strict herbivores that need fresh browse from specific plant species (bramble, oak, and eucalyptus are common depending on species) — this is non-negotiable, not a preference.
How Often to Feed
- Tarantulas: Adults, once every 1-2 weeks. Slings (young tarantulas) can eat more often, twice a week, since they’re actively growing.
- Scorpions: Similar to tarantulas — once every 1-2 weeks for adults.
- Isopods & millipedes: Keep a rotating supply of leaf litter and the occasional vegetable scrap (like a slice of carrot or squash) available; remove uneaten fresh food within a day or two to prevent mold.
- Stick insects: Fresh browse should always be available and replaced every 2-3 days, or sooner if it wilts.
Signs You’re Overfeeding
Uneaten prey wandering the enclosure (stressful for the animal and can attract mites), a visibly overweight abdomen on a tarantula, or mold buildup from excess fresh food are all signs to cut back.
Water
Most species get the bulk of their hydration from prey or food moisture, but a shallow water dish (with a stone or sponge so small animals can’t drown) is standard for tarantulas and scorpions. Isopods and stick insects generally get enough moisture from a correctly humid enclosure and fresh food.
Gut-Loading Prey
Feeder insects like crickets should themselves be fed a nutritious diet for 24-48 hours before being offered — this passes better nutrition on to your pet and is a simple step that’s easy to skip but genuinely matters over the long run.
Choosing Feeder Insects
Crickets are the most widely available and affordable feeder insect, though they’re noisy and prone to escaping if not housed properly before feeding. Dubia roaches are increasingly popular as an alternative — quieter, less prone to escaping, and higher in nutritional value per gram, though they’re slightly more expensive and less universally available. Mealworms work for many species but shouldn’t be the sole diet for most predatory invertebrates, since their nutritional profile alone is less balanced than a rotation of prey types.
Prey Sizing in Detail
The general rule — prey no larger than the width of the animal’s body — exists because oversized prey can genuinely injure a predatory invertebrate during a struggle, and undersized prey may go unnoticed or unhunted, wasting the feeding attempt. For growing slings (young tarantulas), prey size needs to scale up gradually as the animal molts and grows, which means keeper attention to sizing matters more during the fast-growth juvenile stage than with a stable adult.
Feeding During Pre-Molt and Post-Molt
An invertebrate that refuses food is very often simply approaching a molt, not sick — appetite naturally drops in the weeks before shedding the exoskeleton. Offering food during this window is at best wasted and at worst stressful, since a disinterested predator may still react defensively to live prey moving in the enclosure. The safest approach: remove uneaten prey after a reasonable window rather than leaving it in indefinitely, and hold off entirely once molting behavior is clearly underway.
Herbivore Feeding Specifics
Stick insects and similar herbivorous species are far less flexible about diet than predatory species — many are specialized to specific plant families, and offering the wrong plant isn’t just unappealing to them, it can be actively harmful. Always confirm the exact plant species required for your specific stick insect species before sourcing browse, rather than assuming any “leafy greenery” will work.
Common Feeding Mistakes Beyond Overfeeding
- Using pesticide-treated plants as browse or substrate material — a serious and often fatal mistake for herbivorous species.
- Feeding wild-caught insects without knowing their pesticide exposure history.
- Forgetting to gut-load feeder insects, which reduces the nutritional value passed on to your pet.
- Feeding on a rigid calendar schedule instead of watching the animal’s actual condition and adjusting.
Seasonal Feeding Adjustments
Some species show natural seasonal appetite shifts even in a climate-controlled indoor enclosure — reduced feeding interest during typical brumation-adjacent periods for certain species, mirroring what would happen in the wild. This is usually normal and species-specific rather than a health concern, though it’s worth researching whether your specific species is known to do this before assuming a seasonal appetite drop is a problem.
Feeding Multiple Animals in a Shared Space
Communal setups (mainly certain isopod and some social invertebrate species) need enough food distributed across the enclosure to prevent competition, since concentrated food in one spot can create stress or aggression even in species considered generally communal. Spreading food across multiple points in the enclosure reduces this risk more effectively than simply adding more total food in one place.
Storing Feeder Insects Properly
Feeder insects kept on hand between feedings need their own appropriate housing, temperature, and food — an under-cared-for feeder colony produces poorly nourished prey, which undercuts the nutritional benefit even with correct gut-loading right before feeding. Treating feeder insect husbandry as a real, ongoing task rather than an afterthought noticeably improves the nutrition passed on to your actual pet.
Transitioning a New Animal to a Different Feeding Routine
An animal acquired from a breeder or previous keeper may arrive on a different feeding schedule or prey type than you plan to use long-term. Transition gradually rather than switching abruptly — abrupt changes in prey type or schedule can cause a temporary feeding strike even in an otherwise healthy animal, which is easy to mistake for illness if you don’t know a recent transition is the likely cause.
Long-Term Feeder Insect Sourcing
Keepers with larger collections often shift from buying feeder insects as needed to maintaining a small breeding colony of their own, which reduces long-term cost and guarantees supply during shortages. This is a bigger commitment than most beginners need to consider immediately, but worth knowing as an option once a collection grows past a couple of predatory species.
Adjusting Diet for Breeding Females
Female invertebrates being conditioned for breeding often need increased feeding frequency and slightly larger prey compared to a standard maintenance diet, to build the fat and protein reserves breeding requires. This is a specialized feeding phase distinct from everyday care and shouldn’t be applied to non-breeding animals, where overfeeding carries its own risks.
Feeding Considerations for Multi-Species Households
Keepers with several different invertebrate species need to track distinct feeding schedules and prey types per enclosure rather than a single household routine — the biggest practical mistake in multi-species collections is applying one species’ feeding rule across all of them out of habit.
Adapting Feeding for Enclosure Changes
Any significant enclosure change — a move to a larger space, a substrate switch, added enclosure decor — can temporarily disrupt feeding response as the animal adjusts to the new environment, separate from a molt cycle. Give a settling-in period of a week or two before treating a post-change feeding pause as a concern.
Nutritional Supplementation: When It’s Actually Needed
Most invertebrates on a correctly varied diet with gut-loaded feeders don’t need additional supplementation. Calcium dusting on feeder insects is sometimes used for specific species with documented calcium needs, but blanket supplementation without a species-specific reason is more likely to create imbalance than benefit — check species-specific guidance rather than assuming more supplementation is automatically better.
Recognizing a Genuinely Healthy Feeding Response
A strong feeding response — quick prey capture, visible interest — is one of the clearest everyday indicators of overall health in predatory invertebrates, which is exactly why a sudden, sustained drop in feeding interest (outside of an expected pre-molt period) is worth paying closer attention to rather than dismissing.
More Insects & Invertebrates Guides
FAQ
Adult tarantulas typically eat one appropriately-sized prey item every 1-2 weeks, while young slings eat more often — around twice a week — since they're actively growing. A tarantula with a visibly plump, shiny abdomen has likely been fed enough and can go longer between meals.
Yes, and it's the more common mistake among new keepers — overfeeding leaves uneaten prey wandering the enclosure, which stresses the animal and can attract mites, and can lead to an unhealthy amount of weight gain in predatory species.
Species-specific browse (like bramble, oak, or eucalyptus depending on the species) isn't optional — always confirm your species' diet before bringing one home, since substituting an unsuitable plant can be fatal. Local exotic pet stores or invertebrate-keeping forums for your species are the best source.
