Little is known of the form of the appendages in the lowest archaic Arachnida, but the tendency of those of the prosomatic somites has been (as in the Crustacea) to pass from a generalized bi-ramose or multi-ramose form to, that of uni-ramose antennae, chelae and walking legs.
The scorpions use their large chelae for seizing prey and for fighting with one another.
- The same scorpion carrying the now paralysed fly held in its chelicerae, the chelae liberated for attack and defence.
The proportionately enormous chelae (chelicerae) of the first pair of appendages are not provided with poison glands; their bite is not venomous.
5), and that the gnathobases of the chelae which act as the first pair of hemignaths are carried by the third somite.