Glossary: Tarantula-keeping terminology


Old Timer
Dec 8, 2006
I have been seeing a lot of questions about wanting descriptions of common terms phrases, or acronyms and haven't seen very many options for beginners to find them all in one place. With being stuck in the house and all, I had the time to compile a list of terms and phrases I've seen the most questions about. I am by no means an expert, I just love Tarantulas and enjoy learning about them. To the best of my knowledge these are correct, however if something is incorrect, or you have a better definition for these things, please reply and correct me. If you have something you think should be added reply and share the knowledge. Lets learn together! :)

Arachnologist - A person who specializes in the study of spiders and other arachnids.

Arboreal – Species that are adapted for living in trees.

BCF – Blue color form

Bolus – Remaining tissue of prey items and silk after a feeding.

Booklung – The set of four lungs located on the underside of the tarantula’s abdomen that are the openings to the Tarantulas respiratory system.

CB – Captive Bred

Central Apodeme – The indentation located on the carapace.

Cephalothorax – Prosoma, or the anterior end of the tarantula location of legs, carapace, mouth parts, ect

Chelicera - Basal segments of the fangs, used to manipulate prey.

Coxa - Basal segment of the leg connecting it to the body.

Death Curl- The position a tarantula gets into when it is in the process of dying, curling its legs under itself towards its sternum, sometimes flipping over.

Dehydration /(Desiccation / Estivation) - Medical condition resulting in negative fluid balance where the body loses more fluid than it takes in.

DLS – ‘Diagonal Leg Span’ method of measuring tarantulas size by measuring from the tip of the first leg to the tip of the fourth leg on the opposite side.

Dorsal – Top side

Epigrastic Furrow - The opening between the set of book lungs closest to the cephalothorax.

Epigynum – An external genital structure of a female spider consisting of a variably-shaped, hardened plate on the underside of the abdomen with typically one or two openings through which sperm is transferred from a male palpus

EWL - Eggs With Legs

Exuvium - The shed skin or exoskeleton.

Femur – The third leg segment.

Fossorial - Species that are adapted for digging and living underground.

Hemolymph – The blood of the tarantula.

ICU – (Intensive care unit) This is a method of tarantula first aid to keep a close eye on your tarantula and provide a safe controlled environment for you to administer necessary treatment. This is when the tarantula is placed in a small container with a few ventilation holes, lined with dampened paper towels, and a shallow water source. This is used for emergency rehydration. This has the potential to be harmful, as it is a perfect environment for bacteria to flourish and may be uncomfortable for the tarantula.

Impaction – This is when a blockage forms on the tarantulas anus resulting in the it not being able to defecate.

Instar – The period of time after each molt.

Interstitial fluid - The fluid found between cells in the body.

LS - Leg Span

Maxillae –Or the tarantulas teeth, are sharp, rough plates located on the underside of the chelicerae.

Metatarsus - Sixth leg segment.

Molt – (Ecdysis) The exoskeleton of the tarantula. Also what the process of shedding the exoskeleton is called.

Molt Mat – A layer of silk placed down by the tarantula in preparation for a molt.

Nematode – These are parasitic non- segmented microscopic worms found in soil that enter the tarantula through the anus or book lungs, transmitting lethal bacteria and cause irreversible damage to internal structures and organs.

N.E.T - Never Enough Tarantulas

NW - 'New World'. Tarantulas originating from North America and South America are all considered 'New World tarantulas'.

Open Circulatory System - Describes a system where blood (hemolymph) and interstitial fluid are allowed to mix in an organism.

Ocular Tubercle – Part of the carapace where the eyes are located.

Opisthosoma - The abdomen, or posterior end of the tarantula, location of heart, booklungs, silk glands etc

OW - 'Old World'. Species originating from any continent other than the Americas are all considered ‘Old World tarantulas'.

Palpal bulbs - The male's secondary reproductive organs, located at the end of the pedipalps.

Patella – Fourth leg segment.

Pedicel - Connects the opisthosoma (abdomen) to cephalothorax (prosoma) and contains the tissues that connect the tarantulas respiratory, digestive and circulatory systems to both sides of its body.

Pedipalps - The second pair of appendages after the chelicerae used for manipulating prey items. They have 6 segments, as opposed to the 7 on the legs. In mature males, the tarsal segments are modified into secondary sexual organs (papal bulbs).

Post-embryo - (EWL) The stage of development in eggs when the spider's head and legs grow out of the egg.

Prosoma - Cephalothorax or anterior end of the spider consisting of everything before the Pedicel.

RCF - 'Red Color Form'.

Scopulae - (scopula pads or claw tufts) dense tufts of hair at the end of a tarantulas tarsus.

Setae - The tarantula's hairs.

Sexual dimorphism - Differences in appearance, specific to each sex of the same species.

Sling - Short for 'spiderling'.

Spermathecae - The female sex organ, (referred to as a “flap” when sexing tarantulas) located at the base of the sperm receptical holds the sperm in place for fertilizing the eggs released from the ovaries.

Sperm web – A web made by mature males to expel sperm prior to loading the papal bulbs with the sperm.

Spinneret - Specialized funnel-shaped organs located on the rear of the abdomen for secreting silk.

Sternum - The plate located on the dorsal side the prosoma.

Stress curl – the position a tarantula gets in when it is stressed or scared, curling its front legs over its head.

Stridulate – Rubbing together of the hairs on the hind legs to create sound.

Sub Adult - The stage of growth before maturity

Tag – When a tarantula bites something or someone

Tarsus - Seventh leg segment.

Terrestrial – Species that are adapted for living on the ground.

Threat posture – This is defensive posture where the tarantula lifts its front legs over its head to show its fangs. A few NW species will raise abdomen to appear larger. This is meant to warn predators that their next move is too bite or to kick hairs.

Tibia - Fifth leg segment.

Tibial hooks – Hooks located on the tibia of males, used to help hold female in place while mating. Not found on all species.

Trochanter - Second leg segment.

Urticating hairs – small barbed hairs on the tarantulas body that can be kicked off as a defense mechanism, these hairs embed themselves into the skin, eyes, nose and mouth of whatever the tarantula kicks them towards and can cause itching, burning, swelling, redness, and in more serious allergic reactions anaphylactic shock.

Van Der Waals Interaction – ( Van Der Waals Force) Is a distance-dependent interaction between atoms or molecules, occurs between a smooth surface and the setae found on the tarantulas paws. This is what allows tarantulas to walk on smooth surfaces.

Ventral – Underside

WC – Wild Caught

Wet Molt –What it is called when a layer of hemolymph is found between the exoskeleton being molted and the new exoskeleton underneath. The Tarantulas new skin will appear wet, thin and weak after the molt.
They aren't hairs. Technically only mammals have hair.

Your physics term Van... that is not listed correctly, too many capitals.

8 legged

Active Member
Nov 25, 2020
I'm from Germany, and In don't know what L1 or L2 and so on means. Are these the Nymph-Stadiums?


Aug 2, 2020
Very impressive list! Thank you for posting that! There is one that I didn't see though. The Apodeme: A depression on the top part of the carapace that provides a central point of attachment for the muscles.


Sep 5, 2016
This is more common in herp keeping,but still relevant,so I’ll add to this useful update.
Wet bite:a bite with venom injected,and resulting complications.
Dry bite:a bite with no injection of venom (very common),and the result is limited to physical fang damage.