Insect reclassification and Evolution
- SciEnvy
- Jun 25
- 3 min read
Insects are crustaceans that live on land.
Stay with me!
There are already a few famous land insects. Coconut crabs rank among the most impressive, while pillbugs, or woodlice, also spend their entire lives on land, despite having gills.
However, it is increasingly accepted, over the last 10-15 years or so, that any grouping that includes all crustaceans must also include insects. For those among us who are not evolutionary biologists, it works like this: imagine a family group, the Lawsons, with grandparents, parents, and the current generation. Maybe someone dyes their hair green and adopts a new rock-n'-roll persona, totally different to the rest of the family, and drops the name. On meeting the family, you might not immediately see that the rebel is one of them, but you wouldn't be able to talk about 'the Lawsons' without including the musician. This is basically what we think has happened with Crustaceans and insects- you might not be used to calling an insect a crustacean, but its relationship with other crustaceans means it, too, is one.
That might seem pretty far-fetched, but there are some compelling reasons to believe this. Firstly, of the many creepy-crawly type things on this planet- centipedes, spiders, crabs- only insects and crustaceans (think: flies and lobsters) share the same shape of a special focusing crystal in each of their many lenses of the eye. It might seem trivial, but this is consistent from things as different as brine shrimp and caterpillars, or krill and cicadas. It's not just the eyes that are the same, however. The more researchers look at what is called 'molecular' evidence, or: similarities between the DNA and proteins of other crustaceans vs. insects, the more they are convinced of this relationship.
This is despite that the obvious differences- land vs. sea, squished vertically vs. squished horizontally; and so on- reflect profound amounts of time in evolutionary history. Perhaps as much as 500 million years separate the insect lineage. For reference, the earliest Tyrannosaurus rex fossils are around 72 million years old. So, insects have been crawling around for over seven times as long!
Our six-legged friends have taken some surprising turns and detours during this time; one that has resulted in some incredibly unique biology and important impacts on other life forms.
Insects are older than flowering plants- which are perhaps only 150-250 million years old. Or, half as old as the ancestor of insects! Insects are of course famous as pollinators, enabling plants to reproduce, and they were doing this before flowers existed, to plants such as pines. The relationship between pollinating insects and flowering plants has actually enabled both groups to become more diverse, and the success of one would have been impossible without the other. This is illustrated by the fact that Magnolias, the beautifully fragrant cream-white flowering trees which are the descendants of some of the oldest flowering plants, are actually pollinated by beetles. Why? Bees didn't exist yet!
Bees are special for reasons other than being the source of pollination for one-third of our crops. You may be aware that every worker bee (basically, any bee you're likely to ever see out and about) is female, but why? Workers and the queen have two copies of their chromosomes, much like we humans do. Males only have one copy. That means that a female queen creates male bees without any sperm- they simply only put half their DNA in an egg! This fascinating arrangement basically means that a male bee is something akin to a multicellular sperm. They emerge, mate, and die on average in 55 days, compared to a queen's average of three to six years. The peculiarity social structures such as theirs, where a queen is also the only one to reproduce and her daughters provide for her, inspires research in fields like evolutionary game theory to this day.
More examples of strange insect lifestyles:
Some insects are what are called hyperparasites- parasites on insects that are themselves parasitic, an extremely niche and unlikely way to make a living.
Research has suggested the 13- and 17- year cycle of cicada (a kind of 'true bug'), has evolved not once, not twice, but at least EIGHT times in the last four million years!
There are kinds of wasp that live inside of, and ONLY inside of, specific types of tree, such as the oak apple gall wasp.
The insect world is one of the most unusual and interesting in the animal kingdom- and hopefully even more so now that you know they are 'really' crustaceans! So next time an unsuspecting relative is enjoying the dance of butterflies around a garden of flowers, you can be sure to ask them if it's their favorite kind of crustacean.
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