You pick up a rock and stare up at yourself, a small insect with a curled tail and pincers, ready to inflict who knows what. Then you see its companions – tiny white insects huddled underneath. Should you drop the stone and crush them or leave them alone?
What you’ve discovered is a family of one of Britain’s least loved but one of the most caring insects – a catchy tune.
Only about 1% of insect species exhibit parental care. Earwigs are one of them.
The females build an underground chamber and lay 30 to 60 eggs, which they protect from fungi and keep clean by “licking”. If a mole or another burrowing animal scatters her eggs, she diligently collects them again.
They hatch after about 70 days, usually in late winter. Foraging in winter, when predators are hungrier than usual, is risky, but it helps the mother ensure her babies survive to adulthood as they can safely remain in her chamber until they are larger.
By the end of spring, the baby “growths” will have dispersed. The female may then have a second, smaller brood with eggs fertilized by the original mating.
Mother earwigs take parenting seriously. Photo credit: Cleopatra women’s mail order/Shutterstock
Maternal tenderness appears to be built into a catchy tune’s genes, as artificially reared wiglets are later shown to nurture their own babies. Despite the cost of energy, caring parents seize the opportunity to pass on their genes.
In contrast, there is a species of wasp that will seal its eggs in a nest that only has enough food for a few larvae, leaving the strongest to eat its siblings. This is parenting care rather than parental care.
Earwigs are unusual in other ways. They are members of the order Dermaptera (“skin wings”), a reference to their shortened, leathery forewings, also called tegmina. These protect the membrane-covered hind wings. Grasshoppers, stick insects and cockroaches also have skin wings.
Earwigs respond to touch, known as positive thigmotaxis, so they habitually crawl into tight spaces. As an adaptation to this behavior, their hind wings are folded under the tegmina. It’s possible that the name “earwig” comes from their ear-shaped hind wing, which is so intricately folded that it’s been studied for technical solutions from self-folding tents to space travel.
The word “catchy” comes from the Old English “ēare” (ear) and “wicga” (insect). Several types of insects, including flies, moths and crickets, get into people’s ears and must be carefully removed.
But they won’t dig into your brain the stories your older siblings or classmates traumatized you with. Earwigs can enter human ears because they prefer close contact, not because they want to harm you.
When you consider that human activities have wiped out so many insects that nature is in danger of collapsing, the idea that these insects are dangerous is ridiculous.
There are almost 2,000 species of earwigs. Credit: Scott Conner/Shutterstock
Not just for show
The most distinctive feature of European earwigs is their terminal tweezers. Tweezers are used for defence, releasing prey, and in mating rituals. The tweezers are straight in women and curved in men.
They also differ between men. Those with shorter, more strongly curved pincers are called brachylabic. Males with long, straight pincers are known as macrolabics. Macrolabic males are more successful at mating, disrupting ongoing copulation with less well-endowed earwigs.
One study examined the relationship between weapon size and the efficiency of the immune system of earwigs. Forceps size has been found to conflict with hemocyte concentrations. In insects, hemocyte cells are crucial for the prevention of infection. Brachylabic males produced more hemocytes than macrolabic earwigs when infected with bacteria.
Just like us, earwigs can be a social bunch. In the fall, they release a pheromone that attracts other earwigs. This is primarily for mating, but earwigs congregate during hibernation, a bit like ladybugs. Nymphs also produce pheromones to encourage maternal care.
Courtship includes the tweezers. Males wave them in the air and use them to pet and grab the female, but they are not used for mating. The pair connect tail to tail for the semen transfer, which can take several hours.
Males and females can have multiple partners. They can stay together after the female has made a burrow and laid her eggs, but males usually return to the surface to forage, so don’t feed their wiglets.
Are earwigs good or bad?
They carry no known human pathogens, but can emit a light nip with their tweezers. They are sometimes garden or horticultural pests. They damage plants, especially dahlias, lettuce, strawberries, potatoes and roses.
But catchy tunes benefit us too. As consumers of organic matter, they accelerate decomposition in the compost. They are nature’s pest controllers, eating aphids, mites and insect larvae on plants. If you prefer to keep your distance, they can be trapped with a damp rolled-up newspaper or controlled by non-chemical methods including diatomaceous earth (a natural rock that can be crumbled into a fine white powder).
Earwigs enter homes through cracks and crevices and, with their aggregation pheromone, can accumulate in damp basements, pantries, or bathrooms. But they won’t harm your home and won’t breed indoors.
They demonstrate the importance of maternal care and biological compromise. They can help us better design structures that fit into small spaces but can unfold into something much larger.
Perhaps people’s aversion to earwigs is similar to how ants react when you lift a rock and find a sizzling colony. Some researchers believe their sheer numbers threaten human desires for individuality and independence.
Here you interrupt a mostly peaceful family life while Mother and Wiglets are startled by a sudden ray of light. Carefully reinsert the stone. They want to be left alone just as much as you do.
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Citation: Earwigs are the hero single mothers of the insect world, and good for your garden too (2023, January 30) retrieved January 30, 2023 from https://phys.org/news/2023-01-earwigs-hero- mothers-insect-world.html
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