Written by Nancy Miorelli
What if the world went suddenly dark? Or cold? Or both? We all know what fate the dinosaurs had, but what would happen to insects?
Before we get going on a wild goose chase through a tunnel of “What If’s” let’s look at some examples throughout geological history and some modern day insects to help us get an idea of what’s going on.
Ice Ages, Meteorites, and Climate Change
Insects first crawled around on the earth 400 million years ago, predating dinosaurs by about 200 million years. Insects started evolving and diversifying throughout the Devonian Period, which means they survived the Karoo Ice Age. During this period, ice sheets expanded from the south pole over the super continent of Gondwana. Temperatures at the poles dropped drastically, but the tropics most likely stayed about the same. The overall temperature of the earth probably only cooled down by about 5⁰C, so insects remained unscathed during this cooling period. In fact, the largest land invertebrate on record lived during this time and it was an 8 foot millipede.
Is It Getting Hot In Here?
Most of the insects you see today zipping around evolved after the most severe mass extinction event of all time, the only mass extinction event to even affect insects. The time during the Permian-Triassic (P-Tr) extinction was difficult for life because of volcanic activity, increases in greenhouse gases, and the aridity of the landscape. Ninety six percent of all marine species and seventy percent of all terrestrial species disappeared off the face of the planet forever.
Basically, it was very *not* cold and very *not* dark and this is the time that the insects struggled with the most.
While the meteorite 65 million years ago is blamed for the destruction of the dinosaurs, in reality it was a combination of changing climatic events that led to their downfall. This period in time is called the Cretaceous-Tertiary (K-T) boundary and the consequences of this climactic period certainly had their effects. Long cold snaps and decreased solar radiation culled the food sources for many herbivorous dinosaurs, affecting dinosaurs further up in the food chain. Despite the giants dropping like flies, insects were unaffected by catastrophic event.
Many insects are scavengers and had plenty to feast upon during these uncertain times. Other insects, especially flying insects, require diets that produce a lot of energy. However, insects that need to fly tend to have diets comprised of fungus, nectar, pollen, seeds, or animal protein. That, combined with their (relatively) small size, meant they didn’t rely on lots of leafy foliage being present all the time. The insects that were most likely to be affected were those with very specific symbioses tied to specific species of plants and those that eat copious amounts of plant matter, like caterpillars and stick insects. That being said, insects that could diversify their diets to several species, genera, or families were more likely to survive.
During the last ice age 14,000 years ago, the planet only cooled about 6⁰C – just enough to keep snowfall on the northern hemisphere. During this period, insects in the tropics were likely unaffected and those that were previously in the northern hemisphere migrated south.
Insects Are Cooler Than You’ll Ever Be
Insects have all sorts of interesting strategies to handle cold weather. “How cold?” you ask? Well, some spring tails (Collembola) can be found hopping around on snowbanks in temperatures as cold as -16⁰C and survive temperatures down to -45⁰C. And they’re not the only thing that you might see out on the snow. In fact, there are whole ecosystems in the arctic governed by insects. Any insect that lives in a place where there is winter has to survive the winter somehow.
And “somehow” comes in two different forms. Freeze tolerance and freeze avoidance are the strategies of choice. Freeze tolerance means that the insects can just handle being frozen solid and wake back up in the spring. If you live in the States, those friendly little woolly bears you see do this.
Insects that like their blood still liquid use the freeze avoidance strategy, which is the more popular way to handle winters. Some insects hibernate in the ground where they aren’t exposed to lethal temperatures, some insects produce coatings to prevent ice from forming on them, some change their gut chemistry, and others produce antifreeze proteins. Some just decide they don’t really need the whole blood thing, and completely dry themselves out.
Who Turned Out The Lights?
Many cave dwelling organisms either don’t have eyes or have significantly reduced eyes, but will compensate for this in another manner. Usually this means becoming more sensitive to vibrations or having better ways to feel the world around them.
But it’s not just cave dwelling creatures that decided eyes just weren’t worth the effort. Many nocturnal insects have comparatively small eyes but with larger antennae to help them identify the world around them. Compound eyes just aren’t great for seeing in the dark, and the more light you can manage to get in, the lower the resolution is. Eventually compound eyes have their limits, but that’s not to say some insects don’t try.
Insects handle cold and darkness surprisingly well. If we went into another dramatic ice age we’d still expect to see insects, especially in the tropical area. Even in the northern latitudes where it is dark and cold, insects have clever ways to hang out on snow banks, hunker down for the winter, and feel around in the darkness. But the insects you’d be searching for would probably be small and drably colored, scavenging and feeding on moss.
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