BY LARRY BARNES
Like Redfish Lake on a summer Saturday afternoon, the cow parsnip pictured here was hugely attractive to the locals. Upon enlarging the image I discovered at least 21 individual insects mining the riches within the flowers. Eight species are pictured, if you include the plant. It could take years to fully understand their collective ecological roles in the world. If you include their microbiomes — the thousands of bacterial species in and on these tiny creatures — it could take lifetimes. But let’s start with just one: the police car moth, Gnophaela vermiculata.
Earth’s moth diversity is far greater than that for butterflies. There are about 160,000 species of moths compared to only about 18,000 butterflies. Moths are generally nocturnal, while butterflies are mostly diurnal. Moth antennae are usually feathered and butterflies typically have unbranched antennae ending in a tiny club.
The police car moth is already a rule-breaker, being active during the day. It also gathers in fairly large numbers and its vibrant patterns make it easy for predators to spot. Often bright patterns signal toxicity, and so it is with police car moths. The moths “want” predators to see them, which is probably why getting close to photograph them is so easy. Police car moths protect themselves in two biochemical ways.
The moths possess genes that create toxic chemicals that repel predators. They also sequester alkaloid toxins by eating bluebells (Mertensia sp.) and store them in their own tissue. The bluebells make a toxin (lycopsamine) as a deterrent to insects (which is evidently not 100 percent effective because at least the moths can eat them). Once in the gut of the moth, the alkaloid is modified and much of it is excreted. The modified portion is exported to the moth’s outer shell, their exoskeleton, where it provides toxic protection against predators.
Police car moths also fly at night and must defend themselves against bats. Along their abdomens are specialized sound-emitting organs called tymbals that make ultrasonic clicks that bats could easily zero in on. The moths make the clicks only when they detect the sonar of the bats. Like the effects of the moths’ bright coloration on the eyes of birds, the moth’s pattern of ultrasonic clicks delivers a message of unpalatability to bat ears and the bat continues hunting for tastier prey.
Natural selection is governed by costs and benefits. The police car moth must allocate energy to make and modify chemicals that are toxic to their predators. They have evolved resistance to the toxic lycopsamine in the tissue of bluebell plants and the ability to turn them into their own defense. The moths have special organs that communicate sounds to bats. These tactics are not cost free; energy is used to make it all pan out. The benefit — immunity to predation — is a big one but nothing in nature is static.
When we look at nature, we are observing a snapshot in an ongoing evolutionary arms race between organisms. The police car moths appear to have seized a winning strategy for now, but new bird or bat counter strategies that might subvert the moth’s winning hand might only be a few mutations away in the unwritten future of the evolution of life on Earth.
Larry Barnes retired from 26 years as a biology teacher at Wood River High School and is now transitioning to spending more time exploring the natural world.