Ti Families - Thera phosidae (Avicularia, Poecilotheria).
The larger species of Bird's Nest Spiders (Avicularia), the opisthosoma of which is as large as a bantam's egg, undoubtedly attack young birds, and M'Cook gives an account of the capture in its web by an ordinary house spider of a small mouse.
Polymorphism usually occurs, certain individuals having the form of avicularia or vibracula.
- Zooecia of Umbonula pavonella, showing a pair of minute avicularia on either side of the orifice of each zooecium.
The most singular of the external appendages found in the Polyzoa are the avicularia and vibracula of the Cheilostomata.