Tens of thousands of grasshoppers have descended on Las Vegas due to an especially wet winter and spring, according to an insect expert.

Dozens of clips have emerged online of swarms of the insects gathered around lights and covering the sidewalk of the famous strip.

“It appears through history that when we have a wet winter or spring these things build up,” Jeff Knight, state entomologist for the Agriculture Department, told a press conference Thursday.

“Then we’ll have flights about this time of year, migrations and they’ll move northward and they’ll often move as far north as central Nevada.”

This year has seen larger numbers than normal, according to Knight, who identified the bugs as a common desert species called the pallid-winged grasshopper.

Knight pointed out that the insects are harmless and eat vegetation.

“They don’t carry any diseases. They don’t bite. They’re not even one of the species that we consider a problem,” Knight said. “They probably won’t cause much damage in a yard.”

The grasshoppers are all adults, measuring no more than 3.8 centimetres, but with wings that help them fly up to three metres high and end up nine metres away, Knight said.

He estimates they’ll hop out of Sin City within a few weeks, continuing north.

In the meantime, residents can deter them by switching off ultraviolet lights and replacing them with a low UV or amber light instead.

“We’ve seen this in the past, approximately every seven to eight years," Knight said. "But again, it primarily depends on the weather.

“Just scare them out of the way and if they get into a home, just use a vacuum cleaner.”