They're usually too loud to ignore. Every 17-years, massive swarms of periodic cicadas take over.
A group known as Brood X last invaded the state in 2004, and they are due back in 2021. But stragglers, likely from that brood, are showing up now, a whole four-years early.
Entomologist John LaPolla teaches at Towson University. He says it's not that strange to see some bugs this far ahead of schedule.
"For reasons that are not entirely clear, it's been documented that occasionally we'll have early emergences, which is what we're having right now," LaPolla said.
The harmless insects have been spotted all around Baltimore, with bigger clusters popping up in Columbia and Towson. The numbers are expected to grow with the warm weather across region this week.
Periodic cicadas spend nearly their entire lives underground. Crawling out in cycles, and into the trees to shed their skin, becoming adults.
That humming chorus you hear is the cicada's mating call. They sing, mate, lay eggs and die. All in just four to six weeks.
"Those eggs will hatch in a few weeks and the little developing nymphs will fall to the ground."
Burrowing into the soil until they follow their parent's footsteps 17-years-later. Or in some cases, sooner.
Scientists say when cicadas make an accelerated appearance, the group could end up creating new cycles of time-keeping broods.
"It's probably why we have all these different broods in the first place, that this sort of happens and sometimes it takes and you get an emergence of a new brood over all," said LaPolla.
Since this off-schedule visit is still somewhat of a mystery, scientists want you to help figure it out. If you see nymphs, exoskeletons or adults you can use online reporting tools to document the sightings.