GEOSESARMA SP. HALLOWEEN (BLACK LEG VAMPIRE CRAB)
Geosesarma Halloween Vampire Crab
Scientific Classification
Scientific Name: Geosesarma sp. (Halloween)
Common Names: Black Leg Vampire Crab, Halloween Crab, Orange Black Leg, Purple Carnaval
Discoverer: Unknown
Distribution: Central Java, Indonesia
Scientifically Described: No
Availability in Trade: Popular (as of February 2025)
Identification & Characteristics
Geosesarma Halloween is a small, semi-terrestrial crab species that is native to, Indonesia, where it inhabits forest floors near bodies of water.
Carapace: Salmon-orange with bright orange markings that can vary in intensity.
Legs: Black or purple-black, adding to the distinctive appearance.
Claws: Typically deep purple, but can appear brighter under the right lighting.
Eyes: Jet black.
Underside: Dark brown or black.
Size: Adults typically measure between 6-7 cm (2.5–3 inches), including their legs, with the body being around 2–2.5 cm (0.8 inches).
Geosesarma Halloween Vampire Crabs Male
Distribution & Habitat
Geosesarma Halloween is native to Central Java, Indonesia. The natural habitat consists of:
Forest floor burrows: They live in burrows near streams and other water sources, where they can access the humidity needed for survival.
Climbing behaviour: Although largely ground-dwelling, these crabs are capable climbers and will often explore higher terrain. In captivity, they are exceptional escape artists so they need to be in tanks with a secure lid or doors.
Social structure: They are semi-social, tolerating group environments in captivity, though males are quite aggressive toward one another. Females are more focused on burrowing to hide from roaming males that just want to breed. Larger females have been known to kill off smaller males when defending their eggs & babies. This is odd considering once their babies are released they will happily eat them.
When kept in captivity
They need a warm, humid environment, with a humidity level of 75% or higher. A humidifier can be used to increase the humidity, or you can mist the enclosure regularly with a water bottle.
WATER SECTION RULES:
Water temperature: 22–25°C (71–78°F)
PH: Between 7.5–8.0
KH (carbonate hardness): Between 0–10
GH (general hardness) Between 4–16
Ammonia: 0
Nitrite: 0
Nitrate: Lower than 20 ppm
Air Temperature: 22–28°C (71–82°F)
Overnight lows and daily highs are normal, so if your tank goes from 20–30c over a 24-hour period (slowly) that is perfectly fine. This is very similar to what happens in nature. However, you will need a heater for your tank during the colder months of the year.
A small experimental paludarium that will inspire you for a future project
Geosesarma Halloween Diet
These crabs are omnivores and adept hunters. They are not selective in their diet, eating a wide range of food, including both plant matter and small invertebrates. Their varied diet makes them relatively easy to care for in captivity, as they will accept most common crab foods. Here’s a full guide for A healthy Vampire Crab diet in captivity.
Halloween Vampire Crab eating a mealworm
Behaviour & Social Dynamics
Males: While they can be kept in groups, male Geosesarma Halloween are known for their territorial nature and may engage in fights, as evidenced by instances where males lock claws in combat, especially older individuals.
Females: They are less aggressive and more inclined to burrow deeply in the substrate, likely to provide protection and create a safe environment for raising offspring.
As with all species of vampire crabs, they spend the bulk of their time hiding, so don’t expect to see them all that often. Because of this, I like to make ecosystems that look great, with the crabs being an extra bonus I get to see from time to time.
IMPORTANT: You cannot mix multiple species (colours) when keeping them in captivity. They will kill each other pretty quickly.
Geosesarma Halloween Breeding Cycle
The breeding behaviour of Geosesarma Vampire Crabs is aggressive and potentially harmful, especially to females. Males forcibly mate with females, often causing injury or even death. After mating, females carry fertilized eggs under their abdomen instead of releasing them into the water. These eggs take 45-60 days to hatch, during which females hide in burrows.
The offspring develop directly inside the eggs, emerging as fully formed miniature crabs, avoiding a larval stage. The mother releases them near water, where they are left to survive independently. Juveniles, which resemble tiny adult crabs, face threats from both predators (including their parents) and sibling cannibalism. They grow quickly, molt often, and stay near water for the first 3-4 months, during which they are particularly vulnerable.
From 8-9 months, the crabs begin to develop adult colours and exhibit territorial behaviour. By 12 months, they are fully coloured and aggressive, starting their own reproductive cycles. Maintaining genetic diversity by introducing new bloodlines is important to avoid inbreeding in captivity.
Conservation Status
As far as we are aware Geosesarma Halloween is not currently endangered in its natural habitat but if over-collection continues for the pet trade it will be on the endangered species list with Geosesarma Dennerle and Geosesarma Hagen.
Interesting Facts
One of the first species in the Geosesarma genus to be introduced into the aquarium hobby but still doesn’t have an official name. Halloween is just its commonly used trade name.
It thrives in paludarium setups that mimic its natural environment, requiring both land and water areas in its enclosure.
If you want to keep these crabs successfully in captivity make sure you check out this guide.
New to Vampire Crabs?
If you entirely new to vampire crabs or just want a really deep dive into caring for them check out This Guide it covers every aspect to keeping them in great detail. Or you can check out the video below.