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April 19, 2011

Many times I have seen tunnel openings in the sand, lined with cobweb, both at Dokmai Garden and in the nearby jungles. Such tunnels may have a large diameter, 40-58 mm at Dokmai Garden, indicating large spiders. Being a gardener you need to know what is going on in your garden, so I have had an urge to find out what is inside. Sometimes I have tried to fish out the spider, using a stick, but that did not work. Sometimes I have tried to flush them out with water, like when hunting giant crickets, but that has not worked either.

Together with Tropical Gardening School student Shane McCarroll from Canada who is an experienced terrarium keeper and biologist, we studied one hole two days ago, before the thunderstorm which brough 12 mm of rain. The hole was 40 mm in diameter and situated in an irrigated plain lawn with Axonopus compressus grass. At night, we gently touched the cobweb at the opening, and we could see the black hairy legs of a large spider inside, but we could not get a close look. It seemed like a tarantula though. A tarantula is a large hairy spider with fangs moving like a pick-axe (suborder Mygalomorphae), while ordinary spiders move their fangs sidewise like pincers (suborder Araneomorphae).

The name tarantula was originally applied to a large Mediterranean wolf spider, whose bite was believed to cause tarantism, a psychological illness forcing the victim to dance a rapid whirling dance, the tarantella. Today, tarantulas are members of the Theraphosidae family (Mygalomorphae), which makes tunnels, but unlike other large hairy spider families they do not make doors, and they have regular sized spinnerets and eight eyes.

Yesterday afternoon while it was still light we decided to dig out the spider. We dug a pit next to the tunnel opening, and then sheared off layer after layer with a small gardening spade, so that we would not hurt the spider. At 20 cm depth he came out and we quickly sealed his retreat way. His body length measured 40 mm, and with legs he was 85 mm long. It was probably a male, not even fully grown (one more instar  perhaps). As a comparison, we dug out an old empty tarantula hole earlier, which was 36 cm deep and measured 58 mm in diameter. That would indicate a spider with a body length of 60 mm. (It later turned out the hole was indeed inhabited).

We used gloves since some tarantulas can deliver painful bites, but  no arachnid is lethally dangerous in Southeast Asia. The spider moved very quickly, and at one occasion it did display an aggressive position with four legs pointing at us and exposed fangs. We took pictures, notes and measurements for making a proper ID, and then we transferred it to a stainless steel bowl. That did not contain it at all! We switched to a large plastic bin with a lid. The species is the Thai black tarantula: Haplopelma minax (Theraphosidae). It is also reported from Burma, Laos and Vietnam.

How do you separate males and females? The male abdomen is usually smaller than the carapace (where the legs are attached). Generally the males seem to be skinnier all around with a smaller body size in comparison to their legs.  Also, during the breeding season the male pedipalps (small leg-like appendages on either side of the fangs) become engorged with sperm (deposited by the male) as he readies himself to search for a mate

Why are the tarantulas so hairy? The hairs protect them from drowning during heavy rainfall. The hair may also transmit vibrations via cobweb, litter or from changes in the air (both in pressure and movement) indicating the arrival of a potential prey, which is useful for a nocturnal hunter.

What does tarantulas eat? They eat any prey smaller than their bodies, so depending on species: birds, lizards, mice, crickets, larvae.

What does tarantulas drink? Morning dew collected by their webs.  Also they tend to obtain most of their daily water requirements from the animals that they capture.

Can you eat tarantulas? In some parts of the world people do. In Cambodia they are considered Viagra and are eaten deep-fried. Den, our Karen worker from Tak province in northern Thailand, says only old people eat it (deep-fried). The Seehamongkol family knows the tarantula delivers painful bites, and although we are keen insect eaters, we would not eat the Thai black tarantula. The Esan people call it ‘maeng mum’ (corner bug).

How old can a tarantula get? Some female tarantulas can become 25 years old in captivity! A male of this species can reach between two and four years while females can reach 12 years according to terrarium keepers.

Is the Thai black tarantula dangerous? It may deliver a painful bite, but is not dangerous unless you are allergic. Many terrarium holders describe them as ‘evil’, ‘nervous’ and ‘ferocious’, but the cool factor is high and many people wish to show how brave they are. Many are warned that keeping this species should only be left to the advanced tarantula keeper.  Our brief experience indicate it does move with the speed of lightning, and it did display an aggressive behaviour for a minute, but nothing else happened.

Should I eradicate all tarantulas from my monsoon garden? No! They rarely leave their burrow, and if so only at night, so you would hardly ever see them. The only severe risk of getting bitten is when you dig for them or accidentally running into one while out on a midnight stroll. Since they contribute with a chemical free pest control, taking larger prey than most other arthropods, they are a welcome attraction at Dokmai Garden where we salute biodiversity!

Text and photo: Eric Danell Shane McCarroll & Ketsanee Seehamongkol

The Thai black tarantula burrow with crisscrossed threads indicating someone is at home. Diameter 40 mm.

Our wild Thai black tarantula, Haplopelma minax, in its original substrate (sandy).

Handle with care (gloves).

A close up of our Thai black tarantula before we released it on the hill.

The body length is approximately 40 mm

A young arachnologist in action.

Read more:

Frances and John Murphy 2000. An introduction to the spiders of Southeast Asia. Malaysian Nature Society. 625 pages and 32 colour plates.

Tarantulas (Short Description)

The Tarantulas Burrow (very useful care sheet)

The Cobalt Blue Tarantula (Haplopelma lividium)

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