Baby jumping spiders are small enough that a standard fruit fly looks like a serious opponent. Getting the feeder size and species right is the single biggest factor in whether your slings thrive or stall. The good news: the answer is simple and doesn’t change much across the first several instars.
TL;DR: Drosophila melanogaster (flightless fruit flies, sometimes called “mels”) are the only practical feeder for L1–L3 jumping spider slings. From L4–L5, introduce D. hydei (a larger species). From L5–L6 onward, small crickets, bottle flies, and waxworms are options. Feed every two to three days. Never offer prey larger than the spider’s abdomen.
What Is a Sling?
“Sling” is keeper shorthand for spiderling, the juvenile stage immediately following the egg sac. Jumping spider slings are measured in instars: L1 (first instar) through L6 and beyond. Each instar is reached after a molt. Early instars are the most feeding-intensive stage of the spider’s life.
For context on what slings grow into, see our full jumping spider care guide.
Feeding Jumping Spider Slings by Instar
The core rule: prey must always be smaller than the spider’s abdomen. A feeder that is too large causes stress, failed hunts, and can injure the spider. When in doubt, go smaller and feed more often rather than offering something the spider can’t handle.
| Instar | Body Length | Primary Feeder | Feeder Size | Frequency |
|---|---|---|---|---|
| L1 | 1–2 mm | D. melanogaster (flightless) | 0.5–1 mm | Every 2 days |
| L2 | 2–3 mm | D. melanogaster (flightless) | 0.5–1 mm | Every 2 days |
| L3 | 3–5 mm | D. melanogaster (flightless) | 0.5–1.5 mm | Every 2–3 days |
| L4 | 5–8 mm | D. melanogaster or small D. hydei | 1–2 mm | Every 2–3 days |
| L5 | 8–12 mm | D. hydei, small crickets, bottle flies | 2–4 mm | Every 3 days |
| L6+ | 12+ mm | D. hydei, small-medium crickets, waxworms | 4–6 mm | Every 3–5 days |
Why Drosophila melanogaster Is the Only Real Option for Early Slings
Nothing works as well as melanogaster fruit flies for L1–L3. Here is why:
Size match. An L1 jumping spider may be only 1–1.5 mm long. A mel at roughly 1 mm is the only commercially available feeder that fits. D. hydei (the other common fruit fly species) runs 2–3 mm and is genuinely too large for an L1 to take safely.
Movement triggers hunting. Jumping spiders are visual hunters. A mel walking across the deli cup wall produces exactly the movement stimulus that gets an L1 to engage. Prey that is too large or too fast discourages hunting in small slings.
Flightless strains are containable. The “flightless” strains used in the hobby carry a vestigial wing mutation that prevents flight. They cannot escape into your home, and you can open a deli cup and add them without a cloud of flies escaping.
Nutritional adequacy for early development. Mels support healthy molting and growth through the early instars when paired with variety at later stages. They are not a complete lifetime diet, which is why transitioning to larger feeders at L4–L5 matters.
Setting Up Your Melanogaster Culture
You need a live culture, not occasional purchased flies. A single culture produces hundreds of flies over two to three weeks from a single setup. Cultures can be recultured continuously once you understand the process.
The most common sling-feeding mistake is not having a culture running before the slings arrive. A D. melanogaster culture needs five to seven days to begin producing adults after setup. If your egg sac hatches before your culture is producing, you have a feeding gap with no easy fix.
Order or set up your culture at least one week before expected hatch, or the moment you order slings you know will arrive at L1–L2. Keep two cultures running simultaneously. Cultures crash from contamination, temperature spikes, or old age. A backup culture means you are never left without feeders during a critical feeding window.
See our fruit fly culture setup guide for the complete process: media recipes, culture maintenance, and how to start recultured batches from existing stock.
How to Deliver Food to Slings
Delivering feeders to something 2 mm long takes some technique. The method changes depending on your housing setup.
Communal Sling Containers (Multiple Slings Together)
Tap the fruit fly culture gently to knock the adult flies off the lid and sides, then quickly open the culture and tip 10–15 flies into the sling container. Close the culture and the sling container immediately. The flies disperse and the slings hunt on their own schedule over the next 12–24 hours.
Do not count flies carefully. Add a reasonable number and let the slings work.
Individual Sling Containers
A fine artist’s paintbrush (size 00 or 000) is the best tool for transferring one or two flies at a time to a tiny container. Before transferring, chill the fruit fly culture in the refrigerator (not the freezer) for five to ten minutes. Cold fruit flies slow down enough to pick up with the brush tip. They revive within a few minutes once warm, giving you a moving target in the sling’s enclosure.
Alternative: a small funnel made from paper inserted into the culture lid lets you pour a controlled number of flies into a transfer cup.
L4 and Larger
Feeder tongs or fine tweezers work well for D. hydei and small crickets. Offering prey with tongs allows you to confirm the spider takes it and to remove any rejected prey promptly. See our what do jumping spiders eat guide for full feeder variety guidance across all life stages.
Housing Slings for Feeding Success
The enclosure affects feeding success more than most keepers realize.
Small containers are better for early instars. An L1 in a large enclosure may never locate its food. A 32 oz deli cup or smaller is appropriate for communal slings through L3. Individual slings do well in 2–4 oz cups through L3.
Vertical surfaces matter. Jumping spiders are aerial hunters: they stalk from elevated positions and drop on prey. Cork bark, fake plant stems, or even the smooth vertical walls of a clear container give slings hunting vantage points. A flat-floored container with nothing vertical dramatically reduces hunting success.
Sparse decor produces better results. A heavily planted container hides the feeders. Slings in early instars hunt best when they can see flies moving across clear surfaces. Add structure for climbing, but leave clear sightlines.
When to Move from Communal to Individual Housing
Jumping spider slings can share a container through L2–L3 with relatively low cannibalism risk, provided food is consistently abundant. A hungry sling will eat a sibling. A well-fed sling typically will not.
The practical guideline: separate by L3–L4, when you observe any cannibalism at all, or when individual feeding tracking matters to you. Earlier separation is always the safer choice if you have the containers for it. Small deli cups are cheap. The time cost of individual feeding is worth it once slings are large enough to handle their own cup.
Signs a Sling Is Feeding Successfully
Abdomen plumps within a few hours of a feeding session. This is the clearest immediate indicator. Before feeding, an abdomen at the low end of healthy looks slightly flattened. After a successful feeding, it rounds out visibly.
Regular, complete molts. In early instars, slings can molt every two to four weeks. A molt schedule in that range confirms the spider is eating and growing well.
Active, alert behavior. A well-fed sling explores its container, tracks moving objects with its eyes, and positions itself on elevated surfaces to hunt.
Complete molt sheaths left intact. A stuck or partial molt often indicates dehydration or a feeder injury during a vulnerable period.
What to Do When a Sling Refuses Food
A sling that refuses food for more than five days when feeders are available is probably in pre-molt. Look for:
- A darkened abdomen with a slightly dull appearance
- The spider sealing itself into a web retreat or spending more time still
- Reduced interest in prey even when flies walk past it
This is normal. Do not force feed. Remove live prey from the container (live prey can injure a spider about to molt). Wait until the molt completes, then wait another 24–48 hours for the exoskeleton to harden before offering food again.
If the spider is not showing pre-molt signs but is still refusing food, check the prey size. A sling that has grown since your last feeding session may now find its feeder too large. Offer something smaller.
Our jumping spider molting guide explains what a normal molt looks like and when to be concerned.
Transitioning to Larger Feeders at L4–L5
At L4, you can begin offering small D. hydei alongside melanogasters. Hydei run 2–3 mm, which suits a spider in the 5–8 mm range. Many L4s take to hydei immediately. If yours ignores them, continue with mels and try hydei again at L5.
At L5–L6, small crickets become an option. Crickets provide good nutritional variety and trigger strong hunting behavior in juvenile jumping spiders. Size them carefully: the cricket should be no longer than the spider’s abdomen. Quarter-inch (6 mm) crickets work for most L5 spiders.
Waxworms are a palatable treat at L6 and beyond but are very high in fat. Use them occasionally as enrichment, not as a staple. An overdose of waxworms produces an overfed, lethargic spider that goes into an extended fast.
For full adult feeding guidance, see our what do jumping spiders eat guide.
Hydration for Slings
Slings need water on the same schedule as adults, scaled to their container size. One brief fine mist on a single wall of the container every one to two days is enough for L1–L3. The droplets that form are easily accessible to even tiny slings.
Do not let the container sit completely dry. Do not flood it. One corner damp, the rest dry.
The connection between hydration and molting is direct: a sling that is too dry going into a molt is at serious risk of a stuck molt. Consistent misting throughout the instar cycle is not optional.
Common Sling Feeding Mistakes
Offering feeders that are too large. A feeder longer than the spider’s abdomen causes stress and can injure the sling. This is the most common early mistake and the easiest to fix: just go smaller.
Not having a culture producing before hatch. You cannot improvise for L1 slings. They need melanogasters immediately, and a culture takes a week to start producing. Plan ahead.
Opening the culture over the sling container. Fruit flies that escape into your room are a nuisance and can infest food. Do all transfers over a smooth surface or inside a large bag you can close if flies escape.
Removing uneaten feeders immediately. Jumping spiders sometimes stalk prey for hours before striking. Give feeders 12–24 hours before removing them. Exception: remove any prey that is actively harassing the spider, or any prey larger than the spider’s abdomen.
Leaving live prey in the enclosure during a molt. A cricket or even a fruit fly can injure a spider with a soft, freshly molted exoskeleton. When you see a molt beginning (pale, limp spider hanging in an open area), remove all live prey immediately.
Communal housing too long. L1–L2 communal is fine. L3–L4 is the transition window. Communal L5 slings with consistent feeding gaps will cannibalize.
Key Takeaways
- Drosophila melanogaster is the only practical feeder for L1–L3 jumping spider slings
- Prey must always be smaller than the spider’s abdomen
- Have your melanogaster culture producing before slings arrive
- Run two cultures simultaneously to prevent feeding gaps
- Feed every two to three days; abdomen plumpness is the most reliable success indicator
- Transition to D. hydei at L4 and small crickets at L5–L6
- Separate communal slings by L3–L4, or immediately at first sign of cannibalism
- Never leave live prey in the enclosure during a molt