Ladybug love lights up Mt. Diablo

This article was originally published in the Pioneer in 2014.

Clayton resident Debbie McCarthy, a frequent Mount Diablo hiker, stumbled onto one of nature’s more risque shows recently.

While hiking Falls Trail, she and her husband took a rest on a rock, and suddenly realized they were cocooned by swarms of ladybugs all over the branches of nearby trees.

“I sat on the ground to shoot some pictures and a few started crawling on me,” she says. “Many of them were mating. We sat and watched them for about 20 minutes. It was one of the best ‘hike finds’ we’ve had.”

During the late winter months, before the wildflowers bloom but after the December and January chills, hikers along Mount Diablo’s trails are treated to this colorful display: thousands of ladybugs converging on branches, eating, socializing and sometimes engaging in that natural R-rated activity, mating.

Mt. Diablo, nature’s tallest spring-break destination

It is ladybug season in the East Bay, and the lush hills of Mount Diablo are ground zero. In the fall the ladybugs move out of the valley lowlands into the surrounding hills and mountains, gathering in leaf litter, under logs or in rock crevices to hibernate.

They can hibernate in groups of 50 to 100 million, to produce and conserve warmth. Most ladybugs only live for several months.

They are attracted by pheromones and some species will mate in autumn before wintering in these huge groups; others mate in spring after coming out of the winter hibernation. As the weather warms and the beetles disperse the females look for plants on which to lay their eggs.

Every year during winter, hikers walking up the canyons of Mount Diablo remark about finding large congregations, sometimes in the thousands, of brightly orange-red lady beetles. Over 180 species of lady beetles (the more accurate name for ladybugs) live in California. Worldwide there are more than 6,000 species and in many parts of the world, ladybugs are revered and thought to bring good luck.

Certainly many of them are getting lucky in their winter home.

Don’t call them bugs

Not bugs at all, they are VW-shaped beetles with hard, protective outer wings. Their coloration varies from region to region, but many ladybug species are predominantly red-orange with black spots. There are several species in California; the most prominent on Mt. Diablo is Hippodamia convergens. Guided by some inner map, they mass in the same sheltered ravines year after year, dispersing in the spring to search for food.

However winsome they may seem to humans, ladybugs are rapacious armored tanks to their favorite prey, aphids. Because of the beneficial role they played in medieval Europe by ridding gardens and vineyards of aphids, they were reverentially dubbed “Our Lady” beetles, after the Virgin Mary; hence the derivation ladybug (“ladybird” in Britain). Look for swarms of adult ladybugs in dark, shaded ravines, especially on the Falls Trail.

Surprisingly lady beetles are diverse in their habitat, food and coloration. The most familiar to children and adults alike are the oval-shaped red with black spots, the red seven-spotted lady beetle, the plain red California lady beetle or the two-spotted lady beetle.

Adults and the black and orange larva that hatch from the tiny yellow eggs feed on aphids, scale insects, and mealy bugs that can be very destructive to plants. For this reason ladybugs are sometimes collected in these huge colonies and sold as a control for pests in gardens and orchards. It should be noted that one imported variety, the multicolored Asian lady beetle, will congregate during the winter in yards and around homes sometimes causing large “infestations” in buildings.

The bright colors of ladybugs warn predators that they contain a toxic chemical in their bodies that cause them to be distasteful and even unpalatable. A few species, as well as some other insects that do not contain the toxin, mimic the toxic varieties, therefore benefiting from these colors.

Luckily, most hikers aren’t aphids, and are fairly safe from being devoured by the swarms of Ladybugs nesting on the mountain. Besides, it seems as if the ladybugs have something better to do.

Robert Smith and Mike Marchiano of the Mt. Diablo Interpretive Association, and Debbie McCarthy contributed to this article. It was originally published in the Pioneer in 2014.