Ticks are bloodsucking arachnids that burrow into your skin. Before burrowing into your body, they might wander around on your body for over an hour.
Ticks can also be pin sized and their bites are unnoticeable.
They'll also stay attached for multiple days. Although the bites themselves are relatively harmless, they can transmit diseases.
That mole that you're unsure if it's always been there might actually be a tick.
At this point, it should be relatively obvious why we moved a significant amount of recourses from researching mosquitoes to ticks. They're just way better at being stealthy.