Millions of Mormon crickets have invaded streets and buildings in Nevada and are causing intense concern among citizens.

Videos shared on social media and local news outlets show six Nevada counties under… siege by the crickets. A local hospital had to use brooms to clear the way for patients to enter the building, a spokesman for Northeastern Nevada Regional Hospital told local news outlet KSL.

Crickets not only make for scary pictures and videos but also make the roads dangerous when they are infested.

Crickets lay eggs in the summer, which lie dormant in the winter and then hatch in the spring. But this year, due to an unusually wet winter, the hatchlings were delayed. The large numbers of insects moving into Nevada can remain at their peak for four to six years before being brought back under control by other insects and predators, Jeff Knight, an entomologist for the Nevada Department of Agriculture, told the Guardian.

Mormon crickets are a thorn in the side of farmers. They earned their name because swarms of the insects devastated the fields of Mormon settlers in Utah in the mid-19th century. Since then they have continued to destroy corn, oats, wheat, rye and barley, some of the state’s most profitable crops, according to the University of Utah.