Insect Clouds are normal sized insects that act as a group rather than individually. Generally insect swarms will detect movement and follow a player around for a time. While doing so, the player suffers from the Distracting Cloud debuff. If ignored the insect swarm will eventually grow bored and leave the player alone. Players can regain the interest of the insect swarm at a later time.
If aggravated by others, or attacked by the player, insect swarms will retaliate and are quite capable of defending themselves. Unfortunately, insect swarms tend to appear in areas with other, more dangerous creatures which will attack on sight. While defending themselves from one opponent, players frequently attack the swarm accidentally.
As with other Spiders and Insects, insect swarms are weak to Beleriand damage.
A list of all known sightings: