What are glochids?
Glochids are hair-like spines or short prickles, generally barbed. (1)
Glochids are also known as glochidia. (1)
The singular of glochids is glochidium. (1)

What do glochids look like?
picture here, and here (picture here) (1)
hair-ike spines or short-prickles (1)

Where are glochids located?
found on the areoles of cacti in the subfamily Opuntioideae. (1)

1. https://en.wikipedia.org/wiki/Glochid