10 Eggs-traordinarily Odd Eggs

Species that give birth to live young are by far the oddest creatures on earth, at least if you go by the statistics. It is thought that 99% of all species reproduce by laying eggs that hatch outside the mother’s body. Laying eggs is a risky proposition, though, because it increases the chances of something terrible happening to your babies while they are stuck inside their shells.

A dazzling variety of adaptations have evolved over billions of years to give eggs the best chance of successfully hatching. Here are ten fantastical types of eggs you will not find in your local supermarket.

Related: Top 10 Places That Prove Our World Can Be Weird as Hell

10 Monotreme Eggs

When we think of what distinguishes mammals from other groups of animals, we tend to believe that they, and we, give birth to live offspring and feed them milk, but this is not entirely true. A group of mammals called the monotremes still lay eggs. Currently, only two types of mammals, the echidnas and the platypus, are known to do this, and egg-laying mammals are probably more like the ancestral species that all mammals descended from.

The eggs the monotremes lay contain relatively well-developed offspring within them and generally hatch within ten days of being deposited. To escape the leathery eggs they are trapped inside, platypus babies, known as puggles, grow a sharp “egg tooth” made of keratin on their bills to tear the shell casing. Echidna young also develop an egg tooth, which is a feature often seen in reptiles and reflects the evolutionary history of all mammals.^[1]

9 Lacewing Eggs

If you ever see a group of lacewing eggs in your garden, you might think they are suffering from some weird fungal infection. Unlike most insect eggs, lacewing eggs are laid one at a time and at the end of a thin stalk, which holds them away from the plant they are laid on.

Why would a creature lay an egg attached to such a delicate-looking structure? When they emerge from these eggs, lacewing larvae are hungry and carnivorous, so the eggs are deposited near the aphids on which they feed. Oddly, the lacewing is not protecting its eggs from the aphids but from the ants that protect them.

Aphids are often guarded by ants because the aphids produce a sweet liquid from their rear end that is consumed by the ants. By placing their eggs on stalks, the lacewing parents keep them safe from ants until the larvae are sufficiently grown to feast on the aphids.^[2]

8 Mermaid Purses

If you are wandering along a beach, you might stumble upon a small black or brown object that has washed up on the shore. If you pick it up, it is hard to understand exactly what it might be. Folklore has given them the name “mermaid purse” because having mythological marine people using them to store coins almost seems more likely than the reality.

Mermaid purses are the eggshells of sharks, skates, and rays. They are usually made of a tough and leathery material with a rectangular shape with a prong poking out at each corner. These prongs sometimes have thin tendrils spiraling from them, which reveals how the eggs are deposited. The tendrils become entangled with seaweed, which anchors them in place until the embryos within have grown enough to escape and survive on their own.^[3]

7 Spiral Horn Shark Eggs

You might think that the classification of fossils is relatively easy, but that is far from the truth. Some preserved remains confuse even the greatest minds in the field. When examples of a strangely twisted fossil were first discovered, experts thought it must be some type of plant. It was only later that Palaeoxyris was correctly identified as a type of egg—though things might have been cleared up sooner if any of the researchers had seen the egg of a horn shark.

The eggs of a horn shark have a similar spiral shape. They may have evolved to give the baby sharks the best chance of surviving until they are ready to hatch—because the mother shark does not stay around to protect them. It is unclear how the spiral shape is made, but it may be that the gland that produces them in the mother is similarly twisted.

Once the eggs exit the mother, they fall to the seabed where they would be easily consumed by hungry predators if it was not for the strange shape of the egg case. Because of the spiral form, the eggs are more likely to become wedged in out of the way places and between rocks, making it harder for anything looking for an easy meal to get at them.^[4]

6 Drongo Eggs

Cuckoos are cunning parasites. They find a nest where birds of another species have already laid their eggs and then sneak in to deposit their own egg inside. Once the cuckoo egg hatches, the baby bird pushes either the other eggs or the other hatchlings out of the nest. The parent birds then put all their energy into feeding the cuckoo—even as it grows to many times larger than the parent birds themselves. Cuckoos use trickery to make sure their eggs blend in with the eggs already in the nest, as they are able to lay eggs that look almost identical to the other eggs.

How do birds protect themselves from having changelings being snuck into their nests? In the case of the drongo bird, they develop their own personal egg patterns. Cuckoos can still mimic the eggs of the drongo, but they don’t do it quite well enough. Mother drongo birds can recognize their own patterns, almost like a fingerprint, and will destroy the cuckoo eggs before they get a chance to hatch.^[5]

5 Stink Bug Eggs

It should perhaps be no surprise that the eggs of the spined soldier bug, Podisus maculiventris, are also spiny. The small round eggs have openings that are surrounded by short spikes. It is not this odd appearance, though, that makes these stink bug eggs so unusual.

The spined soldier bug is the only species that is known to be able to change the color of its eggs at will. When the insects lay their eggs on the light underside of a leaf, the eggs are almost white. When the same insect lays eggs on the top of a leaf, then they are darker, sometimes black. It is thought that the darker eggs on the more exposed upper surface of the leaf have more protection from ultraviolet light.

No one knows how the insect is able to alter the appearance of its eggs. Researchers are not even certain what chemicals inside the eggs produce the darker colors.^[6]

4 Praying Mantis Eggs

Praying mantises are well known for both their extraordinary prowess as hunters and somewhat unusual mating practices—which sometimes end with the female killing and consuming the male after, or sometimes during, sex. But here, we will focus on the strange structures they produce once they are ready to lay their eggs.

After the mantis mating season, you may spot large, papery objects appearing on branches. Known as oothecae, these structures are produced at the same time as the mother lays her eggs. The mother produces a special foamy substance that covers the eggs and hardens them into the ootheca, which protects the eggs. The ootheca can take a number of shapes, and many of them look like something straight out of a horror film. When the eggs—up to 400—inside hatch, the scene can be equally scary, as a mass of miniature mantises spew out.^[7]

3 Glass Frog Eggs

Glass frogs are a fascinating group of creatures to study and somewhat easy to study internally because they are partially see-through from underneath. This means you can see their bones and internal organs if you flip the frogs over. But here, their eggs and how they develop interest us.

A male glass frog will find a leaf that hangs over running water and begin to make its mating call. When a female comes to the leaf, the pair mate. Then, the female lays its eggs on the leaf, and the eggs stay in place thanks to a jelly-like substance. The female and sometimes the male stay to guard the eggs.

When the eggs hatch, the tadpoles seem trapped, but thanks to gravity, they soon tumble off the leaf and into the water.^[8]

2 Octopus Eggs

While many creatures who lay eggs abandon them as soon as they are out, some species spend a great deal of time caring for their unhatched babies. No group of organisms gives more energy toward guarding their eggs than octopus mothers.

Octopuses sometimes lay hundreds of thousands of small and translucent eggs in a single batch, so there are many reasons to make sure they remain safe until they are ready to hatch. In most species of octopus, the mother will create a den, often dragging rocks around it to ensure it is safe, before laying her eggs.

Once the eggs are deposited the mother octopus will cling to the top of the den and gently fan the eggs to make sure they get the right amount of oxygen. Then she waits. Without feeding, the mother octopus stays in the den to guard the eggs for months. One deep-sea octopus was observed guarding its eggs for four years.

Such a long time without food is catastrophic for the mother. She slowly begins to die as she watches over her eggs. The usual strong colors of the octopus fade to a sickly white; she will not live long enough to care for her young. When the tiny baby octopuses hatch, they immediately swim away to begin their struggle to survive into adulthood.^[9]

1 Elephant Bird Eggs

Had you visited the island of Madagascar a little over a thousand years ago, you might have encountered a bird so large that it is called the elephant bird. The largest example of the elephant bird stood around 10 feet (3 meters) tall, easily dwarfing the largest humans. You would expect the large bird to lay large eggs, and you would not be wrong.

Elephant bird eggs are the biggest of any vertebrate species that we know of. Each egg could reach up to 16 inches (40 cm) in length and hold as much as 120 chicken eggs. To produce even one of these eggs would have been extremely expensive for the elephant bird mother, so if they were stolen or destroyed, it was a costly loss.

No more elephant birds exist, but no one is entirely sure why. Some researchers blame climate change for the loss of habitat for the birds, but others think the human inhabitants of Madagascar are the ones who drove elephant birds to extinction. If mother elephant birds had guarded their nests, it would have to be a brave hunter who tried to raid them.^[10]