Reference library · Arachnid locomotion · Updated September 2026

The Ultimate Valley of Mexico Recluse Spider References for 3D Animators

Measured anatomy, real gait mechanics, verified behaviour and a
12-clip animation list for Loxosceles tenochtitlan — the recluse spider
science only met in 2019, and the one that actually lives in Mexico City’s walls.

Most spider rigs fail in the same three places. The legs bend like elbows instead of
folding like struts. The walk cycle is a mammal gait with four extra limbs bolted on. And
the idle never stops moving, because the animator could not believe a predator would sit
still for forty minutes.

All three mistakes are fixable. The fix is not taste, it is published measurement.
This page gathers what science actually knows about the Valley of Mexico recluse
spider: segment lengths in millimetres, the two leg joints that have no extensor
muscle at all, the share of the night the animal spends frozen, and what it really eats.
Then it turns each number into something you can key.

1. The species file

The Valley of Mexico recluse spider, Loxosceles tenochtitlan,
was described in December 2019 by Alejandro Valdez-Mondragón and colleagues in
ZooKeys
892. It is named for Tenochtitlan, the Mexica city built on an island in Lake Texcoco
that Mexico City now sits on top of.

What makes it unusual is not the venom. It is the address. This is the first recluse
spider considered native to the Valley of Mexico, and its type locality
is a private house — Cruz Verde 132, Tlalpan, at 2,281 m elevation. For decades
these animals were collected and filed under Loxosceles misteca. Morphometrics
and DNA barcoding finally separated them.

2. Reference plates from Wikimedia Commons

The best free imagery of this species is the original description’s own figure set.
The authors released it under CC BY 4.0, so you can use it commercially
as long as you credit it. Full credit lines are in section 15.

3. The measured body

Everything below comes from the type series in the 2019 description. Millimetres, not
vibes.

Overall proportions

Leg lengths, all four pairs

The leg formula is 2-1-4-3: leg II is longest, then I, then IV, then
III. This is the ordering you must respect when you place footfalls, because it makes the
footprint pattern a wide diamond rather than a rectangle.

Inside one leg

A spider leg has seven segments: coxa, trochanter, femur, patella,
tibia, metatarsus, tarsus. Descriptions only measure femur through tarsus, so here is
the male’s longest leg broken down, with each segment as a share of what was measured.

Two numbers there do most of the work. The patella is 5.3% of the leg,
so the famous “spider knee” above the body is not a long segment — it is a sharp
angle change across a short one. And tibia plus metatarsus is 61.8% of
the leg, which is why a recluse silhouette is dominated by two long thin rods meeting at
a shallow angle near the ground.

A rig budget that matches the animal

If you have not rigged a multi-limbed creature before, the generation workflow in
our
Blender Rigify guide transfers directly — you are building eight short IK
chains instead of four long ones.

4. Six eyes, and what they cannot do

Get this arrangement right and arachnologists will forgive you a lot. Get it wrong and
you have modelled a different family. The six eyes sit as one central pair at the front
and one pair set back on each side, leaving conspicuous gaps between the groups.

The violin marking is the famous field mark, and L. tenochtitlan has a
notably well-defined one — the description calls it a “defined pale brown
violin-shaped pattern dorsally, darker toward the ocular region.” But violins vary,
fade, and appear on unrelated spiders. The eye arrangement is the reliable
character. Put your detail budget there.

What the animal actually senses

5. Locomotion: hydraulics and gait

Spiders solved walking in a way no vertebrate does, and the difference is not
cosmetic. It changes your interpolation curves.

Two joints with no extensor muscle

The femur–patella and tibia–metatarsus
joints are the main flexion and extension joints of a spider leg, and neither has an
extensor muscle. The hinge axes sit at the dorsal rims of the segments, so muscles can
only pass the joint on the ventral side — geometrically, a muscle-driven extension
is impossible. Instead the spider extends those joints
hydraulically: dorsoventral muscles compress the prosoma, haemolymph
pressure rises, and the fluid pushes the segments apart.

One honest caveat, from
Weihmann
and colleagues (2012). In large, fast spiders during hard escape accelerations, the
ground reaction force vectors pass dorsally to the leg joints. The hydraulic
mechanism is therefore not doing most of the work at top speed. So use the pressure feel
for walks, stalks and pushes. In a flat-out sprint, the legs are thrown, not
inflated.

The gait: alternating tetrapod

Terrestrial eight-legged animals overwhelmingly use an alternating tetrapod:
the legs split into two sets of four, and the sets alternate. Number the legs L1–L4
on the left and R1–R4 on the right, front to back. Legs L1, R2, L3 and R4 move as
one set. Legs R1, L2, R3 and L4 move as the other. The two sets run half a cycle apart.

Four rules follow from that chart and from the leg measurements above.

1. Every leg shares one cycle period. Leg III is 25% shorter than
   leg II, but it does not step more often. It takes a shorter stride. Animators who give
   short legs faster cycles produce a shimmering mess.
2. The footprint is a diamond. With a 2-1-4-3 formula, legs II plant
   widest and furthest forward, leg III plants closest to the body. Lay your foot targets
   out that way before you touch a curve.
3. The body barely bobs. Four legs are always down and the animal is
   a crevice specialist. Vertical travel on the prosoma should be small — a fraction
   of a millimetre at scale — and its rhythm is twice the stride frequency,
   because both sets push.
4. Turning is stride-length asymmetry. Shorten the inside strides,
   lengthen the outside ones. There is no pivot joint anywhere in the body to bend.

6. What locomotion science found in 2025–2026

Three recent results change how a careful animator handles eight legs.

Spiders re-learn their gait in under a day

In June 2025, Suzanne Amador Kane and colleagues published the first application of
unsupervised machine learning to spider gait data in the
Journal of Experimental Biology. They filmed juvenile tarantulas running
intact, immediately after autotomising two legs, and again one day later.

The finding is striking: the spiders returned to their pre-autotomy speed and
stride frequency within a day, and again after the legs regrew. Path tortuosity
did not change. What did change was posture — autotomised spiders
widened the spread of the remaining legs to cover the missing footprint
and hold stability.

The hydraulic story got more precise

Two 2025 papers refined the pressure picture. One, in the
Journal of Theoretical Biology, modelled semi-hydraulic actuation
and showed that moving haemolymph through the leg does not fight the muscle-driven
flexion — the two systems cooperate rather than compete. Another, in
Arthropod Structure & Development, extended hydraulic function to the
chelicerae, which matters directly here: the fang stroke of a recluse
is partly a pressure event, not purely a muscular snap. Give the bite a
load-and-release feel, with a beat of build-up before the strike.

Distribution is contracting

Not locomotion, but it belongs in any 2026 brief. A 2024 species-distribution study by
Valdez-Mondragón and Cortez-Roldán modelled four central Mexican
Loxosceles and projected that L. tenochtitlan‘s suitable range
shrinks 35–50% by 2050–2080, with only 20–30% of
currently occupied area persisting. Precipitation of the driest month alone contributed
41.8% of the model. A spider that already lives almost exclusively indoors is being
pushed further indoors.

7. Behaviour: where this spider actually hides

This is the section most spider animation gets wrong, because it is the section nobody
looks up. The behaviour of L. tenochtitlan is unusually well documented for a
species described so recently, because the describing team collected it in people’s
homes and wrote down exactly where.

Indoors, in Mexican cities

Every known specimen of this species came from inside a house or
building. The authors state plainly that it was never collected in natural
areas. The type locality is a street address. Here are the recorded hiding places, taken
straight from the description:

The geometry of a refuge

Recluse crevice preference has been measured, on the two best-studied species in the
genus, by Vetter
& Rust (2008). The numbers are unusually actionable for a layout artist:

Three things follow. Your crevice should be vertical. It should be
roughly a finger’s width, not a hairline. And it should look
used — a fresh clean gap is the one a recluse rejects. Dress the
inside with a thin, dusty, irregular silk lining and you have built the exact space these
animals compete for.

In nature

Honest answer: for this species, unknown. It has never been found outside a building.
The niche model puts its natural envelope in the Trans-Mexican Volcanic
Belt around 2,500 m, in temperate and pine-oak forest. Vegetation type alone
contributed 42% of that model. Ecologically, then, this is a highland
forest animal that happens to live in our walls. Elsewhere in the genus, recluses shelter
under rocks, under loose bark, in rodent burrows and in caves. If you need a natural set, build a rock-and-bark version of the same vertical,
finger-width, silk-lined crevice.

The activity budget, hour by hour

8. What it eats, according to the papers

No feeding study exists for L. tenochtitlan specifically. What we have is a
careful field diet study of a synanthropic Loxosceles reclusa population
(Cramer
2015), and it is far more interesting than the generic “eats insects” answer.

Sit-and-wait, not stalk-and-chase

The same study found that these spiders do not actively search for prey.
They sit on a small, irregular network of silk that works as a trip line, and they take
what walks into it. That is a completely different character from the roaming hunter most
spider animation depicts. The hunt is contact, seize, retreat, measured in a
handful of frames, bracketed by long stillness on both sides.

The scavenging argument

Here is a live scientific disagreement you can put in your shot notes.

The defensible position in 2026: a recluse is a sit-and-wait predator that
will scavenge when hungry enough and the carcass is fresh enough, but
does not go looking for corpses. If you want a narrative beat, the hungry-spider-accepts-a-dead-moth
shot is scientifically supportable. A spider preferring carrion is not.

9. The silk nobody expected

Recluse silk is genuinely strange, and it is a rendering opportunity almost nobody
takes.

In 2017 a team from William & Mary and Oxford found something new. Loxosceles
spins a flat ribbon about 50 nanometres thick, not the cylindrical
filament every other spider produces. No other arachnid does this. Along that ribbon the
spider lays down periodic sacrificial loops, anchored by silk-to-silk
bonds with no added adhesive. Under tension the loops pop open one after another. The
thread stretches and relaxes again and again instead of simply snapping, and it absorbs
many times more energy than a plain strand of the same strength.

10. The brown recluse comparison

You will almost certainly be asked “is this the same as a brown recluse?” The answer
is: same genus, same body plan, same rig, different address and different genitalia.

What all recluses share

• Six eyes in three separated pairs. The family signature.
• A flat body on long thin legs, with the 2-1-4-3 formula typical of
  the genus. One rig genuinely serves all of them.
• Chelicerae fused at the base, so the two fang bases move as a
  unit — do not rig them as independent jaws.
• Stridulatory lines on the lateral face of the chelicerae, recorded
  in the 2019 description. That is the file half of a sound-making organ, which means
  these animals have an acoustic channel in their behavioural repertoire.
• Sphingomyelinase D in the venom, the enzyme behind loxoscelism.
  A 2025 study in Int. J. Mol. Sci. split the enzyme into Class I and Class II
  and showed Class I drives markedly stronger dermonecrosis.

11. The 12 core animations

This is the clip list I would ship for a recluse used as a game creature, a
documentary insert or a horror beat. Frame counts assume 30 fps; halve
the swing timings for 60 fps rather than doubling the counts.

The five that carry the performance

01 · Idle_Retreat_Hold — the one you must not skip

Eight legs planted, body low, abdomen touching or nearly touching the substrate. Over
240 frames allow yourself: one slow pedipalp flex, one 1-pixel abdomen pulse every 60 or
so frames, and nothing else. No drifting, no breathing wave, no idle sway. The stillness
is the character. Then cut to clip 05 and the audience jumps.

03 · Walk_Cursorial — the 20-frame cycle

Frames 1–10, set A (L1 R2 L3 R4) is in stance while set B swings. Frames
11–20, they trade. Place foot targets in a diamond — legs II widest and
furthest forward, legs III tucked in. Keep the prosoma’s vertical travel tiny and give it
two bumps per cycle, one per push. Ease-out the extensions, snap the flexions.
That last rule is the hydraulic asymmetry from section 5 and it
is what separates a spider walk from a crab walk.

05 · Freeze_Snap — eight frames of total commitment

From any state, every leg stops within 2–3 frames, mid-stride if necessary. No
settle, no overshoot, no anticipation. Legs that were in the air simply stop in the air.
This is the hardest note to give a good animator, because everything in their training
says to cushion it. Do not cushion it.

06 · Crevice_Squeeze — the signature move

The body flattens and rotates so the widest dimension aligns with the gap, legs I and
II go in first and fold rearward along the body, and the abdomen is the last thing to
disappear. Because the preferred crevice is vertical, play it as a climb
into a slot, not a crawl under a lip. Forty-five frames, with the last ten being just an
abdomen sliding out of frame.

12 · Autotomy_Recover — the 2025 paper as a clip

Leg detaches. Two-second stagger with visible asymmetry. Then the remaining legs
spread wider and the walk resumes at full speed. Do not carry a limp
into the walk cycle — the measured animals did not. A creature that loses a limb
and keeps coming at the same speed is far more disturbing than one that hobbles.

Wiring these into a playable character is the same state-machine problem as any
quadruped. If you are building for a game, the setup in
idle,
walk and run locomotion in Unity maps onto this list directly, with Freeze_Snap as an
interrupt state rather than a blend.

12. Colour, scale and lighting

The palette

These swatches are approximations built from the published colour description plus the
live plates above. They are a starting point for a base colour map, not spectrophotometry.

Three details from the description worth building in. Femur I is darker than
the other femora in males. The violin mark deepens toward the eye
region rather than being flat. And the abdomen darkens
posteriorly, which gives you a free gradient that reads as volume under a single
light.

Scale, and the macro problem

A male is 6.70 mm long. In a scene authored at 1 unit = 1 metre, that
is 0.0067 units, which will fight your viewport clipping, your physics solver and your
subdivision tolerances. Model at 100× and scale down at the end, or
author the whole scene at 1 unit = 1 cm.

Then commit to the macro look, because there is no such thing as a wide-angle shot of
a 7 mm animal. At true macro magnification, depth of field is millimetres deep even at
f/16. Let the abdomen go soft while the eyes are sharp. Animators fight
this because it feels like a mistake. It is the single strongest cue that the audience is
looking at something genuinely tiny.

Lighting the cuticle

• Two speculars, not one. Arthropod cuticle is a thin, hard, slightly
  translucent shell. A tight glossy lobe over a broad soft one sells it instantly.
• Backlight the abdomen. The opisthosoma is soft and thin-walled, so
  a rim from behind glows through it. The prosoma and legs do not. That contrast is the
  quickest way to make a spider look alive rather than moulded.
• Model the trichobothria individually. These long sensory hairs are
  sparse, not a fur coat. A few dozen long ones on the dorsal faces of tibia, metatarsus
  and tarsus, catching a rim light, do more than a million-strand groom.
• Keep the key low and warm. Everything about this species is
  crevices, floorboards and dusty corners. A hard low key with a long shadow reaching out
  of a wall crack is the shot.

13. The latest discoveries, 2019 to 2026

14. The paper library

Everything cited above, in the order you would want to read it.

The species itself

Behaviour, diet and refuge

Locomotion and materials

15. Image credits

Every image on this page is free to reuse under the licence named. Attribution is a
condition of that licence, not a courtesy — keep these lines if you reuse the
images yourself.

• Plates 1–5, and the COI tree — Valdez-Mondragón A,
  Navarro-Rodríguez CI, Solís-Catalán KP, Cortez-Roldán MR,
  Juárez-Sánchez AR (2019), ZooKeys 892: 93–133,
  doi:10.3897/zookeys.892.39558.
  Live-specimen photographs by Jared Lacayo-Ramírez (Plate 1), Martín
  Sánchez Vílchis (Plate 3), José A. Castilla-Vázquez and
  Alma R. Juárez-Sánchez (Plate 4). Licensed
  CC BY 4.0,
  via Wikimedia Commons.
• Six-eye diagram — ThatSpiderByte,
  Loxosceles eye group,
  CC BY-SA 4.0, via Wikimedia Commons.
• Loxosceles reclusa — Centers for Disease Control and
  Prevention, Public Health Image Library #1125. Public domain, via
  Wikimedia Commons.
• Loxosceles rufescens — Marino Linić, Rijeka, Croatia,
  CC BY-SA 4.0, via
  Wikimedia Commons.

16. Frequently asked questions

Is the Valley of Mexico recluse spider the same as a brown recluse?

No, but they are close cousins. Both are Loxosceles, they share the six-eye
arrangement, the flat body, the long thin legs and the 2-1-4-3 leg formula, so one 3D rig
serves both. L. tenochtitlan was described in 2019 from Mexico City and is
separated from its relatives by male palp shape, female seminal receptacles and about
13.8% divergence in the COI barcode.

How big is Loxosceles tenochtitlan?

The male holotype is 6.70 mm long in the body and the female paratype 10.40 mm. Legs
are far longer than the body: the longest leg, leg II, measures 20.98 mm in the male,
giving a leg span of roughly 45 mm. Across the full series, female leg I averages
22.36 mm, so an average female spans closer to 50 mm.

Where does this spider hide indoors?

In wall cracks first, then behind hanging wall decorations, under beds and wardrobes,
inside drawers and storage boxes, around door frames, among stacked timber, under chairs
and tables, and between artificial plants. It prefers vertical crevices of roughly
6–9 mm that already contain spider silk.

What does the Valley of Mexico recluse spider eat?

No study has examined this species directly. In the closely related brown recluse, the
measured field diet was 25% other spiders, 21% beetles, 15% woodlice and 13% crickets.
Recluses are sit-and-wait predators that take prey walking into a small silk trip line
rather than hunting it down, and they ignore more than 80% of dead prey offered to
them.

How do spiders extend their legs without extensor muscles?

Hydraulically. The femur–patella and tibia–metatarsus joints have hinge
axes on the dorsal rims, so muscles can only pass them ventrally and cannot extend them.
The spider compresses its prosoma with dorsoventral muscles, haemolymph pressure rises,
and the fluid pushes the segments open. For animators this means extension eases out
smoothly while flexion can snap — and it is why dead spiders curl their legs
inward.

What gait should a spider walk cycle use?

The alternating tetrapod. Legs L1, R2, L3 and R4 move as one set and R1, L2, R3 and L4
as the other. The sets run half a cycle out of phase, with a duty factor near 0.5 at
walking speed. All eight legs share one cycle period. Shorter legs take shorter strides
rather than stepping more often.

Is it dangerous?

It belongs to a medically significant genus whose venom contains sphingomyelinase D,
so treat any recluse with respect and never handle one. Keep the risk in proportion
though: a documented Kansas household collected 2,055 brown recluse spiders from their
own home over six months without a single bite. These animals avoid people.

Can I use these images in a commercial project?

Yes, with attribution. The plates from the 2019 description are CC BY 4.0, the CDC
brown recluse photograph is public domain, and the eye diagram and L. rufescens
photograph are CC BY-SA 4.0, which additionally requires that any adapted version of
those two images be shared under the same licence. Full credit lines are in
section 15.

Where to go next

Written for animators, modellers and technical artists who would
rather cite a paper than guess. Corrections and better references are always welcome
— especially from anyone with a high-speed camera and access to a
Loxosceles.