Friday, April 12, 2024

Lady Beetle

by Christian Ryan
| August 25, 2020 1:00 AM

I was homeschooled through much of my childhood. During one such session (math, I think?) in autumn, my sister, mom, and I looked up at our ceiling to find hundreds — literally hundreds — of tiny red and black-spotted “aliens” invading our house through an almost invisible space between the edge of a window and the ceiling. Our house was under siege from insects commonly known as ladybugs! They were looking for a safe, warm place to hibernate over the long, cold winter, and our house apparently fit the bill. We were well into the winter vacuuming up the remnants of our autumn invasion. Scientific results are inconclusive as of yet, but I suspect our insect invasion may be part of the reason my mother hates the red and black-spotted insects now.

Though “ladybug” and “ladybird” are the common names given to any member of the coccinellidae family, scientists do not recognize these little guys as true bugs or (for fairly obvious reasons) birds. This is largely because they do not possess special mouthparts designed to extract liquids from plants. They are actually a type of beetle, so you’ll hear scientists refer to these critters as “ladybird beetles,” or simply “lady beetles.” We shall use the latter. The most well-known type of lady beetle is called the seven-spot lady beetle.

Farmers have particular interest in lady beetles because they are one of the primary predators of aphids. As true bugs, aphids are notorious for sapping the juicy bits of plants, laying waste to farmers’ crops. The lady beetles are very efficient at pest control, and just one can eat several thousand aphids in the two to three years of its lifetime (this is quite long for an insect of this size). They show the aphids no mercy, hungrily ripping them apart with their barbed mandibles! Young lady beetles have an appetite for aphids as well. A mother lady beetle will lay hundreds of eggs in the middle of an aphid colony. When the offspring (called larvae) hatch a few days later, they go out on the attack!

Not all lady beetles spend their time munching on aphids. Some species are vegetarian, eating only plants, and farmers don’t like them so much. The Mexican bean beetle and squash beetle are both horrific pests of the plants which give them their name. In years when aphids are low, adult lady beetles may get by on pollen, and some may even resort to cannibalism of younger lady beetles.

We’ve discussed at length the lady beetles’ predatory relationship with the aphid, but what’s eating the lady beetles? Predators of the lady beetle include birds, small mammals, and spiders. That being said, these insects have little to fear from these carnivores because of a special defense. Lady beetles produce a toxic brew of chemicals in their knees that are released when approached by predators. The chemicals don’t kill attacking predators, but they make the beetles taste absolutely awful. Next time that predator spies a lady beetle, it will recognize its bright red and black-spotted wing covers and know it should stay away.

That being said, my cat never got this memo, because she would catch and eat them throughout the winter of our lady beetle infestation. Nevertheless, the lady beetle’s defense mechanism is very adept at keeping most predators at bay, ensuring they can continue their aphid-eating spree.

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Christian can be reached at