Urticating Hairs

“Urticating hairs” is actually a bit of a misnomer – urticating bristles is more correct, since “hairs” grow from follicles and are only found on mammals.  The hair-like bristles found on tarantulas are only superficially similar to hair, they don’t grow from follicles, and in fact they differ greatly in terms of structure, shape, and purpose.

Tarantulas have bristles all over their bodies, and different types are used for different purposes.  Some are used for sensing vibration, some tarantulas have stridulating bristles used to create sounds (the loud “hissing” sound created by some species is created in this way) but the type of most concern to tarantula keepers are those used for defence – the urticating hairs found on the opisthosoma (abdomen) of many new world species.

The term urticating comes from urtica, the Latin word for “nettle”.  These barbed bristles can be kicked or flicked off the abdomen by the tarantula’s rear legs, causing a cloud of these tiny hairs which cause irritation, discomfort and pain when they embed themselves in the skin or eyes of a would-be predator.

bsmithi-bald-spotThe bristles don’t appear at birth, but each time the tarantula moults, new ones are added.  They are loosely attached so that they easily break off when “kicked”, and are covered in barbs.  A number of different types are known, and these have different arrangements of barbs which cause varying degrees of irritation on the skin or mucous membrane (such as inside the nose or throat).  As they are kicked off, the tarantula may develop a “bald patch” on its abdomen, but this will be renewed at the next moult (see picture of a B. Smithi with a clearly defined bald patch)

Anyone working with new world tarantulas possessing urticating bristles must take precautions and care when working with these animals or their enclosures.  Some tarantulas shed bristles as territorial markings, so even if the tarantula is not present, there may well be loose bristles on the substrate or webbing which can still cause problems.

In general, urticating hairs are a minor problem so long as precautions are taken.  For most people, a few hairs on their skin will only cause a minor irritation; some itching which may continue for a few hours.  A more serious problem however is if a person suffers an allergic reaction to the bristles, or if they get into the eyes.  Unfortunately there is no way to know for sure if you’ll be allergic if you’ve not come into contact with them before, so take extra care the first time dealing with any new world species known to kick hairs.

If urticating bristles get into the eyes they can cause a lot of pain, and real damage.  In serious cases they can embed themselves into the cornea causing severe pain and long term problems which will require medical attention, so eye protections is advised.

What if I get urticating hairs on my skin?

urticating-reactionIf you do get hairs on your skin, wash the area thoroughly with plenty of running water.  Monitor the area and try not to scratch.  A solution of 2–2.5% hydrocortisone cream applied to the affected area may help relieve the symptoms, and antihistamine tablets such as those taken by hayfever sufferers have been reported to alleviate the symptoms by some keepers.  For most people, the irritation will subside over a few hours, but if it appears to be worsening or lingering, or if it’s accompanied by swelling or severe redness then seek medical advice (see picture, an allergic reaction to urticating bristles on the skin.  Image sourced from Wikipedia)

What if I get urticating bristles in my eyes?

This is potentially more serious.  Start by washing the eye out with lots of fresh running water, then I would suggest seeking medical advice.  With luck none of the hairs will have embedded into your eye and though sore, it should clear up relatively quickly.  If they have embedded though your doctor will be able to advice on treatment (typically a treatment of topical steroids).

How to avoid problems

The best form of treatment is prevention, right?  First of all, know whether the tarantula you’re dealing with has urticating hairs by researching the species.  Most of the new world Ts that are commonly kept by beginners do have urticating bristles, so unless you’re absolutely sure, assume they do!

Keep an eye on your tarantula’s body language.  You can often tell when a tarantula doesn’t want to be disturbed, and you can often clearly see when they kick hairs.  My B. smithi will often kick hairs as soon as the lid comes off her enclosure, and when that happens the best bet is to keep your distance.  Don’t try and handle or move a T which is flicking, don’t lean over the enclosure or get your face too near, and don’t breath in right over your T or the enclosure (remember, even if the tarantula isn’t present there may well be loose bristles in the enclosure!)

I would highly advise wearing glasses or some sort of eye protection when working with new world tarantulas, particularly those you’ve not worked with before, or which are known to be “flicky”.  Take care when doing cage maintenance, and consider wearing gloves when changing substrate etc.

Don’t rub your eyes or touch your face while working with Ts, and wash your hands straight away afterwards.  You don’t want to transfer loose bristles from your fingers to your eyes!  And finally, be aware that old exuvium (moulted skin) can still possess urticating hairs, so treat them with care in the same way you would a live tarantula!

Sources and further reading

Treating urticating hair reactions – Article on Arachnophiliac.info

Got a pet tarantula? Then wear eye protection – Article on Phys.org

Photo of urticating hairs from T. blondi in a human eye – Rick C. West

Grammostola pulchripes – Chaco Golden Knee Tarantula Caresheet

Grammostola pulchripes

Back to tarantula species list

Scientific Name: Grammostola pulchripes (Simon 1892)
(previously Grammostola aureostriata)

Common Name(s): Chaco Golden Knee

Range: The Chaco region of Argentina, and the Grand Chaco region west of the Paraguay river.

Habitat: Grassland and scrub

Experience Level: Beginner/Intermediate

Type: Terrestrial, opportunistic burrower

Size: Leg span up to around 20cm (8″)

Growth rate: Slow/Medium

Venom: Mild

Urticating hairs: Yes

Temperament: A generally calm and docile species, suitable for beginners though care should be taken due to their large size.


Deriving its common name from the golden stripe on each knee (its former latin name was Aureostriata, meaning “golden striped”) this beautiful species grows to an impressive size, yet tends to be calm and docile.  They are a new world terrestrial tarantula, and opportunistic burrower.   They are reported to be one of the fastest growing species in the Grammostola genus, and they also tend to be quite active, though they tend to prefer using an existing hide rather than digging a burrow.  Combined with their striking looks, their generally calm nature and impressive size, and the fact that they tend not to be shy of staying out on display makes them a desirable species both for the beginner tarantula keeper, and for more experienced keepers looking to add a new impressive spider to their collection.

G. pulchripes is often misidentified as Eupalaestrus campestratus (the Pink Zebra Tarantula) which live in the same region.  Chacos coming from Argentina are less hairy than specimens from the Paraguay population, and it’s thought that there may be a third population in Uraguay.

Keeping G. Pulchripes in Captivity

Chaco Golden Knee copyright Flickr user Óscar MéndezG. Pulchripes, as already mentioned, makes an excellent choice as a first tarantula species.  They are generally low maintenance with no special care requirements, and will thrive given the standard husbandry for generally arid, terrestrial species so long as they are given an enlcosure large enough for such a big tarantula.

For general care requirements, read the basic guide to tarantula care page which gives a good overview of tarantula husbandry.

An adult Chaco Golden Knee will require a large enclosure such as a large plastic or acrylic tank, or a 10 – 15 gallon aquarium with a suitable top.  Provide a deep, fairly dry substrate (4 – 5 inches of coconut coir, or dry potting soil), plenty of ventilation, and a secure lid.  A large piece of cork bark will serve as a suitable hiding place (half a coconut shell won’t be large enough for an adult!), and a large shallow water dish should be provided at one end of the enclosure which can be overfilled to dampen the substrate slightly at one end of the tank.

A diet of large crickets, cockroaches and locusts is ideal.  But as with all tarantulas, feed prey items of a suitable size – no larger than the spider’s abdomen.

One of the attractions of G. pulchripes for some people is their tolerance to being handled.  It’s true that this species in general tend to be docile and fairly tolerant to handling, but remember that every individual tarantula is different and that this species can be fast.  While its venom is mild and this species rarely bites, the fangs on a spider this large are more than capable of doing real damage.  At the same time, a fall from even a very small height would easily kill a tarantula of this weight so handle carefully, only if you understand and accept the risks to both yourself and your tarantula.

Further reading

The Tarantula Keeper’s Guide Stanley A. Schultz, Marguerite J. Schultz. (2009)

What Spider is that?  Gabriel, R. (2005) Eupalaestrus campestratus. Journal of the British Tarantula Society 20(2): 50–54