How to Tell if a Tarantula Is Male or Female (Sexing Guide)

Determining a tarantula's sex relies on molt examination, visual cues, or ventral sexing. Males typically have thinner bodies, longer legs, and emboli (reproductive organs) on their pedipalps, while females lack these and live longer. The most reliable method is inspecting a shed exoskeleton for spermathecae (females) or embolic bulbs (males).

Key Differences Between Male and Female Tarantulas

  • Body Shape: Males are slimmer with longer legs; females are stockier.
  • Lifespan: Females live 20-30 years; males die 1-5 years after maturity.
  • Behavior: Mature males wander to find mates; females stay burrow-focused.
  • Coloration: Males often develop brighter colors post-maturity (species-dependent).

Methods to Sex a Tarantula (With Accuracy Rates)

Method Accuracy Difficulty Best For Risk Level
Molt Examination (Check shed skin) 100% Easy All ages None
Ventral Sexing (Flip tarantula) 95%+ Moderate Juveniles/adults Low (stress risk)
Visual Clues (Body shape, hooks) 70-90% Easy Mature males only None

Step-by-Step: Sexing via Shed Exoskeleton (Most Reliable)

  1. Locate the molt: Collect the entire shed skin (especially the abdomen).
  2. Examine the inner abdomen:
    • Females: Look for a spermathecae (small, paired sacs near the book lungs).
    • Males: Absence of spermathecae; may see epandrous fusillae (tiny bumps).
  3. Check pedipalps: Mature males have bulbous tips (emboli); females have smooth palps.
  4. Compare to images: Use verified sexing guides for your species.

Ventral Sexing (For Live Tarantulas)

Warning: Only attempt if the tarantula is calm. Stress can cause injury or death.

  1. Gently coax the tarantula onto a soft surface (e.g., foam).
  2. Use a paintbrush to lightly flip it onto its back.
  3. Inspect the underside:
    • Females: Look for a flap-like structure (epigynum) between the book lungs.
    • Males: No flap; may see tiny hooks on front legs (tibial spurs).
  4. Return gently: Use the brush to right the tarantula immediately.

Visual Clues in Mature Males (No Handling Needed)

  • Tibial Spurs: Hook-like structures on the first pair of legs (used for mating).
  • Embolic Bulbs: Swollen tips on pedipalps (reproductive organs).
  • Body Changes: Longer legs, thinner abdomen, and often brighter colors.
  • Behavior: Restless, web-less, and may refuse food (seeking mates).

Common Mistakes to Avoid

  • Sexing too early: Juveniles lack clear traits; wait for at least 3-4 molts.
  • Misidentifying hooks: Not all hooks indicate males (some females have them).
  • Relying on size: Females are usually larger, but this varies by species.
  • Stressing the tarantula: Never force ventral sexing if it's aggressive or skittish.

When to Seek Expert Help

If unsure, consult an arachnologist or experienced breeder for:

  • Species with subtle sexing traits (e.g., some Grammostola or Brachypelma).
  • Tarantulas that rarely molt (slow-growing species).
  • Confirming maturity before breeding attempts.