AUSTIN (KXAN) -- Begun, the emergence, has. The great cicada emergence of 2024 is underway. Trillions of the insects are expected to crawl from below the surface to breed before dying off. The last time these specific broods of insects were above ground was in 1803. Cicadas come in two varieties, according to Texas A&M. One type, called annual or dog-day cicada, emerges at the end of summer every year. They typically have a 2-5 year life cycle, making them a fairly common sight in North America. The other type of cicada is called periodic cicada. Identifiable by their red eyes, these insects have a thirteen or seventeen-year life cycle. Broods of cicadas across the country are on these different cycles, meaning they emerge from the ground at different times. This year, two different broods (another word for family) are popping up. Brood XIX emerges every 13 years, while Brood XIII emerges every 17 years. This is the first time their cycles have synced up since Thomas Jefferson was president and the last time until 2245. Where can I see the cicadas? The two broods emerge once underground temperatures reach 64 degrees, typically in late April. The broods won't emerge in the same places, thankfully. Brood XIX is also known as the "Great Southern Brood" and Brood XIII is known as the "Northern Illinois Brood." XIX lives in the Southeast while XIII lives in the Midwest. Some can be spotted near the eastern Texas border. "Cicadas have been doing this in nature since before recorded time. And they have a beneficial impact when they come out of the ground. They aerate the soil. They produce a lot of food resources for things that eat insects, like fish, birds and lizards," said Eric Benson, an entomologist at Clemson University, in an interview with the Associated Press. Cicadas are small, but easily found because they are very noisy. The male insects run their legs together, sort of like a cricket, to make noise and attract a mate. "Periodical cicadas can be quite loud when the males are coursing in huge numbers, but it's not dangerously loud. I would say it's like being at maybe a football game or a sized football game where people are cheering, but they're not going crazy," Benson said. Are cicadas dangerous? Thankfully, no. Cicadas don't eat crops. When they emerge, they do it strictly to mate. Female cicadas lay around 600 eggs. Once those eggs hatch, the baby cicadas will crawl underground for another decade plus. During this time, they will feed on tree sap. "To the average garden or a garden to the average bushes, they do little to no damage. I tell individuals if they're concerned, if they have a pool or a hot tub or some area and they don't want a bunch of bugs flying around, you can cover it. If you have a tree that you're worried about and it's a valuable tree and not too large, you can put netting over it," Benson said. Texas A&M said that the worst they can do is break a tree limb after landing on it.