Thlaosoma pennum Celaenia penna is a species of Araneidae spider that is native to New Zealand.

[1] This species was described as Thlaosoma pennum in 1887 by Arthur Urquhart from a single specimen collected in Waiwera.

The cephalothorax is creamy white with brownish streaks.

The abdomen is creamy white with brown shading anteriorly.

[4] Like other members of Celaenia, the species specialises in capturing male moths, which it attracts at night time.