CALCBIOME — JUMPING SPIDER CALCULATOR

How much should your jumping spider eat?

Fruit flies, flies or roaches: what size, how many and how often, what to do around molts, and what size enclosure, by species, size and temperature.

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My jumping spiders

Name

Species

Body length (cm)

Situation

Temperature (°C)

Without legs. A spiderling leaving the sac is 2–3 mm (0.2–0.3 cm); an adult female Phidippus regius is about 1.5 cm.

Abdomen

Molt

Last molt date

What to feed

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How much to feed a jumping spider? The basics

Prey: fruit flies for spiderlings, then flies, small crickets or small roaches. Never wild-caught insects (pesticides, parasites). Mealworms: rarely.
Size: prey no bigger than its abdomen, and at most as long as its body.
Frequency: spiderlings every 1–3 days, juveniles every 3–5 days, adults every 5–7 days (gravid females: 2–4 days). The abdomen matters more than the calendar.
Molts and water: if it seals itself in its hammock, don’t feed it. A few drops of water on one wall every 1–3 days; no water dish needed.
One per enclosure (they eat each other). Never release exotic species: Phidippus regius comes from the south-eastern USA. Local species: collect few, never in reserves, and release them where you found them.

Example for an “average” species at 24 °C

Length	Prey	Per meal	Frequency	After molt
0.3 cm	Melanogaster fruit flies	2	every 2 days	wait 2 days
0.5 cm	Hydei fruit flies	2	every 3 days	wait 2 days
0.8 cm	Hydei fruit flies	4	every 4 days	wait 3 days
1.2 cm	House flies	2	every 5 days	wait 5 days
1.5 cm	Green or blue bottle flies	1	every 6 days	wait 6 days
2 cm	Green or blue bottle flies	2	every 7 days	wait 7 days

These are average guidelines. Every spider is different: the abdomen matters more than the calendar.

How we calculate

Maximum prey size (mm) = spider body length (cm) × 10, i.e. at most as long as its body.
Amount per meal: about 25–30% of the spider’s estimated weight, using the best-suited prey (fruit flies, flies, small roaches), with at most 4 prey per meal.
Days between meals = (1.2 + 2.9 × length) × temperature × abdomen. Flat abdomen × 0.7, swollen × 1.8; under 18 °C × 2, 18–20 °C × 1.4, 20–22 °C × 1.15.
Wait after a molt (days) = 1 + 3 × length, between 1 and 7 days.
Enclosure: width ≈ 4–5 × body length, height ≈ 6–8 ×.

Example

1.5 cm female Phidippus regius, 24 °C, normal abdomen: prey up to 15 mm, 1 green or blue bottle fly every 6 days, and a 6-day wait after a molt.

Sources: UF/IFAS (Phidippus regius), Josh’s Frogs, The Bio Dude, Jackson 1978 (P. johnsoni development). These are guidelines: the abdomen matters more than the calendar.

Frequently asked questions

How often should I feed an adult jumping spider?

Usually every 5–7 days, a little more often for a gravid female. If the abdomen is swollen and shiny, wait.

What should I feed a spiderling?

Flightless fruit flies (melanogaster), 1 to 3 every 1–3 days, in a small container so it can find them.

My jumping spider stopped eating. Should I worry?

Usually not: it seals itself in its hammock before a molt. Remove the prey and leave it alone.

Does it need a water dish?

No: a few drops on one wall every 1–3 days are enough, without spraying the spider.

What size enclosure?

Taller than wide: about 20 × 20 × 30 cm for an adult Phidippus regius, with cross-ventilation.

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