A stroll through the East Bay Regional Parks in Oakland will normally embrace visitors in a vast cloak of greenery. But during the winter months, they may also notice peculiar streaks of red across branches and vegetation stems. No, it’s not evidence of a gruesome crime — it’s a sign of the annual gathering of the ladybugs.

Every November zillions of ladybugs, technically lady beetles, gather in Redwood Regional Park to dine on aphids during their annual migration from the Central Valley. The numbers of the bright red insect swell in December as the congregation coats tree limbs and hemlock stems in a telltale swath of red.

“It’ll pretty much change that branch or piece of a vegetation into shimmery red,” said Pamela Beitz, East Bay Regional Parks head of pest management. For the record, ladybugs don’t count as pests, in fact Beitz said they help manage the park’s aphids.

“Lady beetles perform a pretty important ecosystem service for us, they prey on pests,” said Beitz. “From a pest management standpoint we love to see the lady beetle population thriving.”

While this year’s numbers may be down a bit from previous years, possibly because of the drought, the annual gathering was in full swing. Beitz waded into the brush on a recent rainy morning, pointing out a log covered in a blanket of squirming red beetles.

“Sometimes when they’re on the ground,” Beitz said, “people don’t even see them. They walk by millions of lady bugs and it looks like a carpet of moving beetles.”

No one is exactly sure why the park became one of the few destinations for the annual migration. The beetles will normally remain until February, eating and reproducing until heading off for other points unknown.

“I think we only see ladybugs converge and aggregate like this in certain valleys and rivers and waterways,” Beitz said. “This is where they end up coming back down from their migration.”

The areas where the ladybugs prefer to converge are generally about a mile-and-a-half hike into the park. On rainy days the beetles often become more visible, climbing to the tops of vegetation where they’re easy to spot. The sight draws visitors to the park throughout the winter to see the strange spectacle.

“It’s very fun to see,” said East Bay Regional Parks’ Justin Neville. “It’s fun to come out on a nice rainy day and explore the park and see the ladybugs kind of huddle together.”

Beitz said people have a strong connection with ladybugs, mostly because of their bold red colors of course, but also for their long arduous migration.

“I think we’ve developed kind of a mythical relationship with them and we use them as symbols,” Beitz said. “The lady beetle is a symbol of nature.”

Indeed it’s hard to imagine visitors flocking to the park to witness a gathering of flies or mosquitoes. And of course flies and mosquitos don’t have many poems written about them.

“Lady beetle, lady beetle fly away,” said Beitz, reciting a politically correct version of the famous poem, before whipping out her phone to take one last picture.