This glossary explains common terms you will encounter in the tarantula hobby. It is designed as a practical reference for keepers, whether you are just starting out or have been around long enough to argue about substrate mixes. This glossary will be updated regularly!
A
Abdomen
The rear body segment of a tarantula. It contains vital organs and is the most fragile part of the spider.
Arboreal
A tarantula species that lives primarily in trees and elevated structures rather than on the ground. Some arboreal species (e.g. Phormingochilus sp.) do tend to burrow as slings.
Autotomy (Appendotomy)
The ability of a tarantula to voluntarily drop an appendage as a response to stress, defense or injury.
B
Book Lungs
Respiratory organs located on the underside of the abdomen. Tarantulas have two pairs of book lungs.
Burrower
A tarantula that spends most of its time underground, often sealing itself in during pre-molt. In the hobby they are often called pet holes.
C
Carapace
The hard upper part of the prosoma that protects the brain and major organs. It also houses the eyes and foveal groove.
Chelicerae
The paired mouthparts that hold the fangs and inject venom.
Crickets
A common feeder insect, notorious for its smell, noise, and ability to cause problems if left unattended.
D
Death Curl
A posture where the legs are tightly tucked underneath the body. Commonly caused by severe dehydration or death.
Detritivore
An organism that feeds on waste and decaying matter, such as springtails, mites, or roaches.
E
Enclosure
The container or habitat where a tarantula is kept.
Embolus
The tip of the mature male pedipalp used for sperm transfer.
Ecdysis
The biological process of shedding the old exoskeleton (exuvium) during growth. In tarantulas, ecdysis is commonly referred to as molting and is a vulnerable period where disturbance should be avoided.
Eggs with Legs
A hobby slang term describing very early-stage tarantula spiderlings directly after hatching. At this stage, they resemble tiny moving eggs with legs and are largely immobile, relying on yolk for nutrition before becoming active slings.
F
Fang
The hollow structure used to inject venom and subdue prey.
Feeder Insects
Live prey such as crickets, roaches, or worms offered as food.
G
Genus
A taxonomic rank above species, such as Grammostola or Poecilotheria.
Gravid
Refers to a female tarantula carrying eggs.
GBB
Abbreviation for green-bottle blue, the trivial name of Chromatopelma cyanopubescens, a popular arboreal species.
Gut Loading
The practice of feeding nutrient-rich foods to feeder insects before offering them to a tarantula. This improves the nutritional value of the prey and helps provide vitamins and minerals that the tarantula would otherwise miss.
H
Hemolymph
The tarantula equivalent of blood. Loss can be fatal, especially from injuries to the abdomen.
Hide
A structure that allows the tarantula to feel secure and reduce stress.
I
Impaction
A condition where the tarantula cannot expel waste properly.
Invertebrate
An animal without a backbone, including tarantulas.
Instar
A developmental stage between molts in arthropods. Each time a tarantula completes ecdysis (molting), it enters a new instar. Early instars (slings) are more sensitive to dehydration and environmental changes, due to the lack of a waxy coating.
J
Juvenile
A tarantula that is no longer a sling but not yet fully grown.
K
Key Lock System
The concept that male and female reproductive organs must match for successful mating. This mechanism prevents cross-species mating, each species has it’s unique sexual organ morphology.
L
Leg Span
The diagonal measurement from the tip of one front leg to the opposite rear leg.
Lethargy
Unusual lack of movement or responsiveness.
M
Molt
The process of shedding the exoskeleton to allow growth.
Mygalomorphae
The infraorder that includes tarantulas and other spiders with downward-facing fangs.
N
Nematodes
Parasitic roundworms that are often fatal to tarantulas.
New World
Tarantulas originating from the Americas, typically possessing urticating hairs.
O
Old World
Tarantulas from Africa and Asia, lacking urticating hairs but often having stronger venom.
Opisthosoma
The scientific term for the abdomen.
OBT
Orange Baboon Tarantula, the common name of Pterinochilus murinus. Also known as “Orange Bitey Thing”, a defensive Old World species.
P
Pedipalps
Appendages near the mouth used for handling food and reproduction.
Pre Molt
The period before a molt. Recognizable by behavioral changes, refusal to eat and darkening of the abdomen.
Pet Hole
A joking term for tarantulas that rarely leave their burrow.
Pet Rock
A tarantula that remains motionless for long periods.
Q
Quarantine
Isolating new animals to prevent the spread of parasites.
R
Rehousing
Moving a tarantula into a new enclosure.
Regeneration
The ability to regrow lost appendages over later molts.
S
Sling
Short for spiderling, a very young tarantula.
Spermathecae
Female reproductive organs used to store sperm. Learn more about the anatomy here.
Stridulation
The production of sound by rubbing specific body parts together. In tarantulas, stridulation is used as a defensive warning signal and can sometimes be heard as a faint hissing or rasping sound when the spider feels threatened.
Substrate
The material covering the enclosure floor. Substrate determines how well the tarantula can burrow and how well the enclosure holds humidity. Check out the Ultimate Guide to Tarantula Substrates.
T
Terrestrial
A tarantula species that lives on the ground, often in shallow hides or burrows.
Theraphosidae
The spider family that includes all tarantulas.
U
Urticating Hairs
Barbed hairs used by many New World tarantulas for defense.
V
Venom
A substance injected through the fangs to subdue and break down prey tissue. Tarantula venom is a complex mixture primarily made up of proteins and peptides, including neurotoxins. For humans it is generally not medically significant and rarely dangerous, unless a person has a severe allergic reaction.
Ventilation
Airflow within an enclosure. Ventilation is crucial to prevent stagnant air. Tarantulas respiratory system relies on air movement along the book lungs.
W
Water Dish
A shallow container providing constant access to water.
Webbing
Silk structures used for anchoring and sensing vibrations.
Waxy Coating
A thin lipid layer on the exoskeleton that reduces water loss. In small slings, this layer is not fully developed.
X
Xenesthis
A genus of large, fast growing New World tarantulas from South America.
Y
Yolk
A nutrient reserve used by spiderlings, during the eggs-with-legs stage. Stored in the egg.
Z
Zoophobas
Refers to Zoophobas morio, commonly known as superworms. These beetle larvae are frequently used as feeder insects for tarantulas and other invertebrates. They are nutritious but very active and capable of biting, so they should be pre-killed or supervised closely when offered as food.
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Is My Tarantula Dying? Common Behavior and Emergencies ExplainedForeword The health and well-being of our eight-legged friends is important to every keeper, which is why accuracy matters in an article about emergencies. If you are an experienced keeper or have a background in invertebrate medicine and notice anything that could improve the information in this guide, I welcome your suggestions. You can reach me at contact@nocturnalfangs.com. Disclaimer: This guide is based on current knowledge and practical experience, but it is not a substitute for professional veterinary advice. What Counts as an Emergency? Not every behavior is dangerous, but knowing how to react to tarantula emergencies is part of good husbandry. Many new keepers panic the first time their spider stops eating, hides for weeks, or flips onto its back. The truth is that most of these situations are normal parts of tarantula behavior. However, there are a few circumstances where quick action can make the difference between life …