By Paul Belz
“How many ladybug species do you think live in California?” East Bay Regional Parks naturalist Michael Charnofsky asked a group of 100 ladybug seekers.
“100,000!” an eight year old boy called. Michael laughed and stated that around 175 species live in California, while approximately 5,000 species live across the world. Tens of thousands of red and black spotted convergent ladybugs (Hippodamia convergens) gather every year for the winter in Oakland’s Redwood Regional Park, but nobody really knows for sure why they come to exact certain locations.
Investigators believe that these ladybugs probably spend spring and summer in coastal areas. They pass their time feasting upon soft-bodied insects, especially aphids, small insects that are the bane of local gardeners. “In its lifetime, a ladybug can eat 5,000 aphids,” Michael said. “Aphids are small, but ladybugs aren’t that big either!”
“What are their predators?” a hiker asked.
“One flew in my mouth once!” another hiker exclaimed. “They taste terrible.”
“Most animals would agree,” Michael said. “Ladybugs excrete a yellow substance when they’re scared.” This toxin doesn’t kill the predator, it just tastes lousy. The color red is often a natural warning that an animal is unpalatable. Any animal that’s tried to eat a ladybug will recognize and avoid them in the future.
The number of aphids drops as autumn brings cooler weather. Ladybugs, like many animals, use hibernation as a survival strategy during cold times when food is scarce. “To reach their hibernation locations, ladybugs probably follow the wind currents,” Michael said. Investigators believe that ladybugs make use of the winds blowing inland from the coast to migrate to their hibernation locations in cool areas of the coastal range, such as Redwood Regional Park.
Rising air carries them up the slopes of the East Bay hills, and down into Redwood Regional Park. The new arrivals find scent markers from the previous seasons’ ladybugs to find the places where their parents gathered during the previous winter. Hikers often find huge clusters hibernating on fence posts, trail markers, tree stumps, on the ground, under leaf litter, and many other surfaces.
Some researchers speculate that the ladybugs aggregate to stay warm. Michael questioned this hypothesis- “Why would they cluster in this location here if they wanted to stay warm?” he asked. The canyon where the Stream Trail passes through is colder in winter than surrounding areas of Redwood Regional Park, other parts of Oakland, and the coastal areas. Like all ectothermic or “cold blooded” animals, ladybugs’ body temperatures fall when they come to a cooler habitat. They need less energy to live, so they can hibernate and survive without needing to eat.
The group hiked along the Stream Trail, toward the foot of the Prince Trail where tens of thousands of ladybugs had gathered earlier in the winter. Michael described Redwood Regional Park as a healthy second growth forest. Perhaps some of the world’s largest trees grew here until the region was clear-cut during the 1840s through the 1860s. The forest is protected now. “Maybe in a thousand years it will be similar to the way it was before the 1840s,” Michael said. A chickadee called “Chick-a-dee-dee-dee!” from the shaded forest. Redwood Creek, which supports trout that swim from San Leandro Reservoir, rang with rushing water.
Michael said that the thousands of ladybugs that gathered near Prince Trail had left already, wakened by the early warm weather. Many others remained near a lower meadow. The group photographed them as they clung to fence posts, trail markers, and blackberry shrubs.
They become active and mate on warm, late winter days like this one. They may aggregate so they can find mates. ”When they’re out eating aphids during the summer, they can’t necessarily find each other,” Michael said. “When they gather to hibernate there are lots of other ladybugs to choose from.” This generation will return to the Coast to eat, lay eggs and die. Their children will hatch, eat aphids through the summer, and perhaps return here next autumn to continue the cycle.
The group found a large group of yellow mushrooms with remnants of delicate veils dangling from their caps. “Fairies live around here,” an excited five year old cried. She found no fairies, but was thrilled to find the ladybugs!