Major sub-groups


  • embryonic cuticle of the second maxilla bears an egg tooth, which allows the pupa to escape during hatching
  • first pair of walking legs modified into a clawlike appendage, housing a poison gland near its tip and used to capture prey
  • second segment (trochanter) of trunk legs is ring-like, leading to lack of mobility at the joint with the prefemur
  • nucleus of the spermatozoan has a spiral ridge
  • anterior respiratory system with a single pair of spiracles on the lateral sides of the head capsule
  • absence of eyes or any visual sensory organs
  • labium with outer sensory cones
  • female spermathecae (sac used to contain spermatozoa) formed by paired lateral pockets in the mouth cavity
  • an unpaired genital opening
  • pair of silk-producing spinnerets on terminal segment
  • anal segment with a pair of large sense calicles (trichobothria), each with a long sensory seta
  • branched antennae with a special sensory organ, the globulus
  • eyes reduced to paired sensory spots (pseudoculi) on lateral sides of the head capsule
  • exsertile vesicles on the ventral side of the first postcephalic segment - these can be protruded
  • trichobothria at margins of the tergites
  • pairs of metameres fused into diplosegments
  • antenna with eight articles, the distal article bearing apical sensory cones (primitively four cones)
  • immotile, aflagellate spermatozoa 

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