Why Do Doodlebugs Walk Backward?

Have you ever seen an insect that prefers to walk backward instead of forward? Meet the doodlebug! These insects, also known as antlions or Myrmeleon, are masters of backward motion. While most bugs scurry forward to get around, doodlebugs choose to do things differently. They shuffle backward through the sandy soil, creating perfect cone-shaped pits to catch their prey.

What Is A Doodlebug?

The doodlebug is the larvae of the antlion, an insect belonging to the family Myrmeleontidae. There are about 2,000 species of antlion in the world. They are most common in tropical regions. However, there are a few species that exist in colder temperate regions. These insects are typically found in dry and sandy environments where the larvae can easily dig their pits.

Antlions are winged insects with two pairs of translucent wings and a long abdomen. They may look like dragonflies or damselflies. However, you can easily spot an antlion by its clubbed antennae. The antennae are about as long as its head and thorax combined. Males typically have longer abdomens with an extra lobe, while females have more variation in their abdomen tips. Females lay their eggs and then leave them to hatch.

The antlion larvae (the doodlebug! aka baby antlion) has a thick, spindle-shaped body and a large abdomen with three pairs of walking legs. Its flexible “neck” connects to a wide, flat head with large, curved jaws that are sharp and hollow. The mandibles have grooves that form a channel to inject venom and enzymes to immobilize and digest prey.

When the larva reaches its full size, it forms a cocoon and changes into an adult insect. It creates a round cocoon using sand or other local materials. It sticks these materials together with fine silk. After about a month, the larva transforms into an adult. The adult insect is much larger than the larva. Antlions are unique for having one of the biggest size differences between larva and adult among insects that undergo complete metamorphosis. This is because the adult’s exoskeleton is very thin and light. Adults usually live for about 25 days, but some can survive up to 45 days.

Walking Backwards: How and Why

While most insects prefer walking forward, doodlebugs have specially designed short, stubby legs that work best when moving backward. Their bodies are covered in nearly invisible curved hairs that help them glide smoothly through the sand.

The doodlebug has a broad, flat, oval-shaped body, like a tiny pancake with legs. The most striking feature is its head, which has sharp, sickle-shaped jaws that look like tiny curved swords.

Their oval-shaped abdomen works like a tiny plow, easily pushing through the soil. Their flat head acts just like a shovel, helping them flip sand out of their way as they move. This unique body shape helps them dig their perfect pit homes while moving backward in a spiral pattern.

You might wonder why they move backward at all. Well, their body is perfectly designed to push sand aside. It’s like having a built-in bulldozer. This design makes it much easier to build their traps. Their flattened abdomen helps them stay stable while they work.

Doodlebugs have learned that walking backward in a spiral pattern is the fastest way to build their pit traps. This technique helps them create a perfect pit within 15 minutes.

Doodlebug Hunting Strategies

The doodlebug’s pit-trap construction for catching food process starts after finding an ideal spot in dry, loose sand. The insect marks its construction site with a circular groove. Then, it uses its body like a tiny bulldozer. It plows backward in a spiral pattern, going deeper and deeper into the sand.

Doodlebugs are super picky about their building materials. They carefully sort through the sand. And, they throw out larger grains to make their pit extra slippery. This isn’t just being fussy – it’s a brilliant strategy mixed with engineering. The fine sand helps create what scientists call the “angle of repose” – the steepest possible slope that won’t collapse.

It takes about 15 minutes to complete this masterpiece. The finished pit is quite impressive – measuring up to 2 inches deep and 3 inches wide. But what makes these pits truly unique is their perfect cone shape and carefully maintained walls.

These dedicated builders constantly maintain their traps to keep them in perfect working order. The doodlebug repairs damage to the pit walls by throwing sand. This action restores the slope to its ideal angle of about 31 degrees. This maintenance is so important that without it, the pit’s effectiveness drops significantly over just 12 hours.

When the pit is finished, the larva hides at the bottom, with its jaws wide open and sticking out. The steep walls of the pit guide prey into its mouth while preventing sand from collapsing. This trap is one of the simplest and most effective in the animal world. The fine grain lining creates large avalanches of sand that carry the prey. The loose sand on the sides makes it easy for small insects, like ants, to slip in. The larva quickly grabs any prey that falls in. If the prey tries to climb out, the larva throws sand at them, pushing them back down. This also weakens the walls, causing them to collapse and bring the prey down.

Experienced doodlebugs can catch their prey in record time. Studies show that their capture success increases as they perfect their technique. The most successful hunters are those who maintain perfectly conical pits – they can catch their prey almost instantly. However, sometimes it takes a very long time for prey to fall into the trap. This happens when ants are scarce in the area or there are some other type of outstanding circumstances. Doodlebugs will sit in their traps motionless and waiting up to a month (that we know of)!

Doodlebugs use a clever defensive strategy. These insects can play dead for unpredictable periods, which leaves their predators (birds love eating doodlebugs!) confused. Scientists found that these insects can remember and learn from vibrations in the sand, helping them become better hunters. They can even tell the difference between big and small prey just by feeling tiny movements in the sand.

Research shows that experienced pit-building males have much higher mating success than newcomers. The most successful pairs are those where both partners have previous experience. They are twice as likely to find each other compared to inexperienced couples. And they can remember exactly where they’ve been successful before. They remember their best hunting and mating spots.

Why The Name Doodlebug?

The term doodle originated in the 17th century as a derogatory term for simple-minded individuals. Over time, it evolved into a verb meaning to waste time. It wasn’t until the mid-20th century that it became associated specifically with drawing and scribbling. The meaning of doodlebug used to be idiot. Nowadays, it refers to someone who constantly draws.

The name connection to this particular insect exists because of its pit-building behavior. When the doodlebug moves from pit to pit, it leaves long squiggly walking lines in the sand. It looks like the bug is scribbling, or doodling, in the sand.

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