-idium, -idion

(Greek: smaller or lesser; little)

Inflammation of the mastoid antrum (cavity in the petrous, or hard and stony, portion of the temporal bone that communicates with the mastoid sinuses and epitympanic, or membranic, recess of the middle ear).
The envelope or coat of certain fungi, such as the puffballs and earthstars.
pygidium (s) (noun), pygidia (pl)
1. The posterior or back part of the body in certain invertebrates, primarily insects, crustaceans, and worms, when forming a distinct segment or division.
2. Etymology: from New Latin which came from Greek pugidion; from puge, "rump".
Information is located at Chemical Element: rubidium .
1. In orchid flowers, a sticky disc at the end of the stalk of the pollinium, by which it is attached to an insect's head.
2. A sticky substance in flowers used to collect pollen or pollinia; entomological orchid pollination uses the viscidium dually.

When an insect initially becomes engaged with a second flower of a compatible species, the viscidium of this flower grabs the pollinia off of the host insect's back or head and sends the genetics down the column to the ovary of the flower which is located in the stalk.

If the insect is lacking pollinia clusters to implant into the viscidium, it simply receives a coating of sticky matter which will in return collect pollinia from the anther cap as it disengages the flower.