Assertion: arthropod's pair | /r/HasProperty | fused into single one
Facets:
value: in the majority of spiders
type: OTHER
value: in the middle
type: LOCATION
Source sentences:
text: The trachea were originally connected to the surroundings through a pair of openings called spiracles, but in the majority of spiders this pair of spiracles has fused into a single one in the middle, and moved backwards close to the spinnerets.