Are All Spiders and Tarantulas Venomous?

The basic answer is yes; all spiders and tarantulas are venomous (although, there are a few that are not). However, that does not mean they are all dangerous. There are about 40,000 species of spiders recorded, and only about 200 are considered medically significant to humans! That means only 0.5% of all the spiders in the world are potentially dangerous to people! The vast majority of spiders are safe and not dangerous to humans. For tarantulas, the news is even better; there has never been a recorded death from a tarantula bite ever. See our post for more information about this topic.

Spiders and tarantulas are categorized under the order Araneae. Anything under the Araneae order is considered a spider. “The most important synapomorphies of the Araneae (which would indicate their monophyly) are the following (Coddington, 2005; Coddington and Levi, 1991): (l) abdominal extremities transformed into spinnerets; (2) abdominally located spinning glands; (3) chelicerae with venom glands; (4) male palp modified for sperm transfer; and (5) loss of abdominal segmentation” (1:335). This is how we classify spiders. They must contain venom glands; therefore, all spiders and tarantulas are venomous, but again, that does not mean they are all dangerous! 

Many animals are venomous that are not dangerous to people. For example, honey-bees are venomous, but unless you are allergic (as with all venomous animals), you will not die from an envenomation; it would hurt a little bit or itch, and that is it. Another example of this would be fire-ants. So just because spiders and tarantulas are venomous, does not mean they are dangerous. Most spider and tarantula venom will have little effect on a person.

Here is a quote from Biology of Spiders: “Tarantulas (mygalomorphs), despite their large size, are much less dangerous than is commonly thought. A tarantula bite, it is true, is deadly for mice or insects, but for a human it is usually no worse than a wasp sting (Schanbacher et al., 1973). The venom consists of various polypeptides (molecular weight 5,000-20,000) and is most likely a neurotoxin (Perret, 1973; Lee et al., 1974; Escoubas et al., 2000). In a detailed analysis of a tarantula venom (Eurypelma), the following low-molecular-weight components were found: ATP, ADP, AMP, glutamic and aspartic acid, γ-aminobutyric acid, and glucose; a high-molecular-weight protein (molecular weight 40,000) was identified as the enzyme hyaluronidase (Savel-Niemann, 1989). It might be added that American tarantulas are rather docile and bite only if provoked, whereas African (Pterinochilus) and Asiatic species (Poecilotheria) are a bit more aggressive and can inflict painful bites. Although it may be safely said that a tarantula bite is not dangerous to humans, it is usually deadly for dogs (Isbister et al., 2003). The European tarantulas (Lycosidae; fig. 1.9) have never deserved their bad reputation, which has stuck to them since the Middle Ages (Crome, 1956b). The symptoms of tarantism were probably related to many other causes ranging from other spider bites, notably those of the black widow, to epilepsy.” (1:56-57)

If you believed that all spiders are dangerous to humans, I hope this helps change your view of spiders to the beautiful and interesting animals that they are.

John 15:13 “Greater love has no one than this, that one lay down his life for his friends.” – Jesus the Messiah

Works Cited

  1. Biology of Spiders, 3rd Edition by Rainer F. Foelix


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