Articles: Defensive Mechanism

Pissed off young Aphonopelma seemani
(F. O. P-Cambridge, 1897)

Most of keepers especially the newbie sees spiders only as a venomous creatures, unfortunately, that is not the only defensive mechanism build into them. There are several other mechanism that may effectively kick you out from the hobby for lack of knowledge. For New World Species, most of them possessed an extra one or two defenses against its predators (defensive mechanism), Urticating Hair and Poop Cannon. Poop cannon are merely a turd that harmless, which can buy they some time to flee, usually aiming directly to the eyes of its predator. But Urticating Hair can cause some discomfort. Some more than others, ranging from mild itching, burning and rashes. For your information, there are few type of Urticating Hair usually possessed by tarantula:

Type I (0.2-0.6 mm) - The tarantula will also kick hairs with leg IV at the face of predators, usually aiming for the eyes.

Type II (0.5-1.5 mm) - The tarantula must rub its abdomen against its target, which they must made contact to the predetor. (Avicularia spp., Iridopelma spp. and Pachistopelma spp.) Exception for some Avicularia spp. that can kick hair.

Type III (0.3-1.2 mm) - Urticating bristles are most efficient for defense against vertebrates and invertebrates (Type I kicking method). (Theraphosa spp., Nhandu spp., Megaphoboema spp., Sericopelma spp., Eupalaestrus spp., Proshapalopus spp., Brachypelma spp., Cyrtopholis spp., Iracema spp. and other genera of subfamily Theraphosinae)

Type IV (0.06-0.2 mm) - most irritating to mammalian predators. (Type I kicking method)

Type V (???-?? mm) - Urticating bristle is typical of the species of genus Ephebopus spp. They are located on the pedipalps. They are much shorter and lighter in contrast with other types of urticating bristle.

There a some new world species, does not possessed any type of Urticating Hair:

Acanthopelma spp.
Catumiri spp.
Guyruita spp.
Hemiercus spp.
Holothele spp.
Ischnocolus rubropilosus
Oligoxystre spp.
Proshapalopus spp.
Psalmopoeus spp.
Schismatothele spp.
Sickius spp.
Tapinauchenius spp.

For Old World Species, they did not possessed any of these fancy mechanism, they only rely on their speed (e.g: Stromatopelma calceatum are very fast) and very potent venom (e.g: Poecilotheria spp. known for their potent venom) which store beneath their fang. Most of the species, prefer to flee rather than stand in a fight. Note that, there is no such thing as aggressive in tarantula vocabulary, it defensive, which there are actually very fearless species that seeks out a fight, usually when cornered. The only warning that they possessed are the threat pose and some of other species may hiss (e.g: Pelinobius muticus actually hissing) to warn the predator. If the threat pose or hissing doesn't effective, then they will show you their only way to say "fucking leave me" with a quick bite and retreat.

Now you know why they're so serious..=)