Goliath bird-eating tarantulas are the largest spiders by mass in the world (the giant huntsman spider has a larger leg span), belonging to the genus Theraphosa. They can have a body length of 5.1 inches and a leg span of a foot. At the time I started keeping tarantulas in the late 1970s, there was only one species known, Theraphosa blondi (though at the time it was being sold as Theraphosa leblondi). Blondi, described in 1804, was thought to be the only species of goliath until in 1991, the goliath pink foot (Theraphosa apophysis), was described. Then, in 2010, the burgundy goliath (Theraphosa stirmi) was described. Though all three species look similar as adults, the spiderling and juvenile stages show the greatest differences between species.
Theraphosa blondi (Latreille, 1804)
Theraphosa blondi (Latreille, 1804) is a stunning and remarkable spider from Brazil, French Guiana, Surinam, and Venezuela. The growth rate is very fast. This can be attributed to the warmer temperatures and higher humidity that this species requires. Females are said to be able to live up to 25 years whereas males have a shorter lifespan, from 3 to 6 years. They are nervous spiders despite their large size. They will readily flick their urticating hairs at any threat. Goliaths are one of the few tarantulas that can make an audible noise as they can hiss when they feel threatened. They produce this sound through stridulation, which is when they rub their legs together that have specialized hairs creating a hissing sound. Though they come from the tropical jungles of South America, since they live on the ground under the canopy of trees, their daytime temperatures are a lot cooler than one would expect from a rainforest environment. Their deep burrows create a cooler and more humid area as well.
The differences between Theraphosa blondi and the other two Theraphosa species are that they have setae on the patella and below as well as on the bottom side of the femur. The chelicerae are short in appearance and the carapace is flatter. Mature males lack tibial hooks, found in apophysis. Spiderlings have brown tarsi and dark palps, not found in apophysis or stirmi.
Theraphosa apophysis (Tinter, 1991)
Theraphosa apophysis (Tinter, 1991) has a dusty brown appearance with reddish to pink setae on the legs and abdomen. This species is generally calm but can be skittish if disturbed. This will either cause them to flick urticating hairs or display a threat pose, accompanied by a hissing sound caused by stridulating the bristles between the fangs. The urticating hairs are reported to be some of the worst to come into contact with, causing severe itching and burning. From Brazil and Venezuela, they live in deep burrows and can be often seen at the entrance of their burrow, waiting for prey to come by. Like the other two Theraphosa species, they have a fast growth rate. Though the venom is considered mild, a bite would still be extremely painful due to the size of the fangs.
The differences between Theraphosa apophysis and the other two Theraphosa species are that they have much more setae, especially on the bottom sides of the legs. The coloration is a pink to reddish hue. Spiderlings have eight pink tarsi and palps.
Theraphosa stirmi (Rudolph & Vienmann, 2010)
Theraphosa stirmi (Rudloff & Weinmann, 2010) is from Guyana. Females can live up to 20 years, with the males living from 3 to 5. Like the other two species, they are nervous and will readily shed urticating hairs or start stridulating in an impressive threat pose. These spiders live in deep burrows and can be often seen at the entrance of their burrow, waiting for prey to come by. Like the other two Theraphosa species, they have a fast growth rate. Though the venom is considered mild, a bite would still be extremely painful due to the size of the fangs.
The differences between Theraphosa stirmi and the other two Theraphosa species are that they do not have setae on the patella or bottom sides of the femur. The chelicerae are large, causing the carapace to be less flat than in blondi. Mature males lack tibial hooks. Spiderlings have four pink tarsi and dark palps.