Phalangas (or falangas), also known as camel spiders and wind scorpions (because of their speed) are  Solifugae, a class of Arachnida. The largest species grow to a length of 12-15 cm (5-6 in), including legs. However they are not poisonous. While they will bite people, they pose no threat to life at all.

So there is a mystery here. Either Gurdjieff is misleading us or he has believed the common rumor that camel spiders are poisonous or he has simply chosen the wrong word to describe the spider that bit Pogossian. (There are some poisonous spiders in the Middle East.)