Psychically, insects can appear in dreams as some kind of threat.
This is one reason why they are often used in psychological thrillers and science fiction.
Some form of spiritual ‘infection’ may have taken place. Fleas are symbolic of the type of disruption that is likely to hurt, rather than destroy, such as gossip.
A mantis represents deviousness, particularly of a spiritual kind.
It is that trickster part of us that can create problems when things are effectively working out for us; it is that aspect of our personality which perhaps preys on the other parts and will not take its place within our overall integration. More positively, insects such as ants can appear in dreams as reminders of instinctive behaviour.