Tag Archives: cockroach

Episode 191: Masters of Disguise!

Thanks to Nicholas and Pranav for their suggestions which led to this episode about animals that are especially good at disguising themselves!

If you’d like to listen to the original Patreon episode about animal mimics, it’s unlocked and you can listen to it on your browser!

Don’t forget to contact me in some way (email, comment, message me on Twitter or FB, etc.) if you want to enter the book giveaway! Deadline is Oct. 31, 2020.

Further watching:

An octopus changing color while asleep, possibly due to her dreams

Crows mobbing an owl!

Baby cinereous mourner and the toxic caterpillar it’s imitating:

The beautiful wood nymph is a moth that looks just like bird poop when it sits on a leaf, but not when it has its wings spread:

The leafy seadragon, just hanging out looking like seaweed:

This pygmy owl isn’t looking at you, those are false eyespots on the back of its head:

Is it a ladybug? NO IT’S A COCKROACH! Prosoplecta looks just like a (bad-tasting) ladybug:

The mimic octopus:

A flower crab spider with lunch:

Show transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.

This week let’s look at some masters of disguise. This is a suggestion from Nicholas, but we’ll also learn about how octopuses and other animals change colors, which is a suggestion from Pranav. Both these suggestions are really old ones, so I’m sorry I took so long to get to them. A couple of years ago we had a Patreon episode about animal mimics, so I’ll be incorporating parts of that episode into this one, but if you want to listen to the original Patreon animal mimics episode, it’s unlocked so anyone can listen to it. I’ll put a link to it in the show notes.

Most animals are camouflaged to some degree so that they blend in with their surroundings, which is also called cryptic coloration. Think about sparrows as an example. Most sparrows are sort of brownish with streaks of black or white, which helps hide them in the grass and bushes where they forage. Disruptive coloration is a type of camouflage that breaks up the outlines of an animal’s body, making it hard for another animal to recognize it against the background. Many animals have black eye streaks or face masks that help hide the eyes, which in turn helps hide where their head is.

But some animals take camouflage to the extreme! Let’s learn about some of these masters of disguise.

We’ll start with a bird. There’s a bird that lives in parts of South America called the cinereous mourner that as an adult is a pretty ordinary-looking songbird. It’s gray with cinnamon wing bars and an orange spot on each side. It mostly lives in the tropics. In 2012, researchers in the area found a cinereous mourner nest with newly hatched chicks. The chicks were orangey-yellow with dark speckles and had long feather barbs tipped with white. While the researchers were measuring the chicks and making observations, they noticed something odd. The chicks started moving their heads back and forth slowly. If you’ve ever seen a caterpillar moving its head back and forth, you’d recognize the chicks’ movements. And, as it happens, in the same areas of South America, there’s a large toxic caterpillar that’s fluffy and orange with black and white speckles.

It’s rare that a bird will mimic an insect, but mimicry in general is common in nature. We’ve talked about some animal mimics in earlier episodes, including the orchid mantis in episode 187 that looks so much like a flower that butterflies sometimes land on it…and then get eaten. Stick insects, also known as phasmids, which we talked about in episode 93, look like sticks. Sometimes the name just fits, you know? Some species of moth actually look like bird poop.

Wait, what? Yes indeed, some moths look just like bird poop. The beautiful wood nymph (that’s its full name; I mean, it is beautiful, but it’s actually called the beautiful wood nymph) is a lovely little moth that lives in eastern North America. It has a wingspan of 1.8 inches, or 4.6 cm, and its wings are quite lovely. The front wings are mostly white with brown along the edges and a few brown and yellow spots, while the rear wings are a soft yellow-brown with a narrow brown edge. It has furry legs that are white with black tips. But when the moth folds its wings to rest, suddenly those pretty markings make it look exactly like a bird dropping. It even stretches out its front legs so they resemble a little splatter on the edge of the poop.

But it’s not just insects that mimic other things. We’ve talked about frogfish before in episode 165. It has frills and protuberances that make it look like plants, rocks, or coral, depending on the species. The leafy seadragon, which is related to seahorses and pipefish, has protrusions all over its body that look just like seaweed leaves. It lives off the coast of southern and western Australia and grows over nine inches long, or 24 cm, and it moves quite slowly so that it looks like a piece of drifting seaweed. Not only are the protuberances leaf-shaped, they’re green with little dark spots, or sometimes brown, while the body can be green or yellowish or brown like the stem of a piece of seaweed.

Many animals have false eyespots, which can serve different purposes. Sometimes, as in the eyed click beetle we talked about in episode 186, the false eye spots are intended to make it look much larger and therefore more dangerous than it really is. Sometimes an animal’s false eyespots are intended to draw attention away from the animal’s head. A lot of butterflies have false eyespots on their wings that draw attention away from the head so that a predator will attack the wings, which allows the butterfly to escape. Some fish have eyespots near the tail that can make a predator assume that the fish is going to move in the opposite direction when startled.

Even some species of birds have false eyespots, including many species of pygmy owl. The Northern pygmy owl is barely bigger than a songbird, just six inches tall, or 15 cm. It lives in parts of western North America, usually in forests although it also likes wetlands. It’s mostly gray or brown with white streaks and speckles, but it has two black spots on the back of its head, fringed with white, that look like eyes. Predators approaching from behind think they’ve been spotted and are being stared at.

But some larger birds of prey have false eyespots too, including the American kestrel and northern hawk owl. What’s going on with that?

You’ve probably seen or heard birds mobbing potential predators. For instance, where I live mockingbirds will mob crows, while crows will mob hawks. The mobbing birds make a specific type of angry screaming call while divebombing the predator, often in groups. They mostly aim for the bird’s face, especially its eyes, in an attempt to drive it away. This happens most often in spring and summer when birds are protecting their nests. Researchers think the false eyespots that some birds of prey have help deflect some of the attacks from other birds. The mobbing birds may aim for the false eyespots instead of the real eyes. Despite its small size, the northern pygmy owl will eat other birds, and it’s also a diurnal owl, meaning it’s most active during the day, and it does sometimes get mobbed by other birds.

Sometimes, instead of blending in to its surroundings, an animal’s appearance jumps out in a way that you’d think would make it easy to find and eat. But like the cinereous mourner chicks mimicking toxic caterpillars, something in the mimic’s appearance makes predators hesitate.

A genus of cockroaches from the Philippines, Prosoplecta, have evolved to look like ladybugs, because ladybugs are inedible to many predators. But cockroaches don’t look anything like ladybugs, so the modifications these roaches have evolved are extreme. Their hind wings are actually folded up and rolled under their carapace in a way that has been found in no other insect in the world. The roach’s carapace is orangey-red with black spots, just like a ladybug.

In the case of a lot of milkweed butterfly species, including the monarch butterfly, which are all toxic and which are not related to each other, researchers couldn’t figure out at first why they all look pretty much alike. Then a zoologist named Fritz Müller suggested that because all the butterflies are toxic and all the butterflies look alike, predators who eat one and get sick will afterwards avoid all the butterflies instead of sampling each variety. That’s called Mullerian mimicry.

A lot of insects have evolved to look like bees, wasps, or other insects with powerful stings. The harmless milksnake has similar coloring to the deadly coral snake. And when the mimic octopus feels threatened, it can change color and even its body shape to look like a more dangerous animal, such as a sea snake.

And that brings us to the octopus. How do octopuses change color? Is it the same in chameleons or is that a different process? Let’s find out and then we’ll come back to the mimic octopus.

We’ve talked about the octopus in many episodes, including episodes 100, 142, and 174, but while I’ve mentioned their ability to change color before, I’ve never really gone into detail. Octopuses, along with other cephalopods like squid, have specialized cells called chromatophores in their skin. A chromatophore consists of a sac filled with pigment and a nerve, and each chromatophore is surrounded by tiny muscles. When an octopus wants to change colors, its nervous system activates the tiny muscles around the correct chromatophores. That is, some chromatophores contain yellow pigment, some contain red or brown. Because the color change is controlled by the nervous system and muscles, it happens incredibly quickly, in just milliseconds.

But that’s not all, because some species of octopus also have other cells called iridophores and leucophores. Iridophores are layers of extremely thin cells that can reflect light of certain wavelengths, which results in iridescent patches of color on the skin. While the octopus can control these reflections, it takes a little longer, several seconds or sometimes several minutes.

Leucophores are cells that scatter light, sort of like a mirrored surface, which doesn’t sound very helpful except when you remember how light changes as it penetrates the water. Near the surface, with full spectrum light from sunshine, the leucophores just appear like little white spots. But water scatters and absorbs the longer wavelengths of light more quickly than the shorter wavelengths. We’ve talked about this before here and there, mostly when talking about deep-sea animals.

To make it a little simpler, think of a rainbow. A rainbow is caused when there are a lot of water droplets in the air. Light shines through the droplets and is scattered, and the colors are always in the same pattern. Red will always be on the top of the rainbow because it has the longest wavelength, while violet, or purple, will always be on the bottom because it has the shortest wavelength. The same thing happens when sunlight shines into the water, but it doesn’t form a rainbow that we can see. Red light is absorbed by the water first, which is why so many deep-sea animals are unable to perceive the color red. There’s no reason for them to see it, so there’s no need for the body to put effort into growing receptors for that color.

Blue, by the way, penetrates water the deepest. That’s why clear, deep water looks blue. Solid particles in the water also affect how light scatters, so it can get complicated. But to get back to an octopus with leucophores, the leucophores reflect the color of the light that shines on them. So if an octopus is deeper in the water and the light shining on it is mostly in the green and blue spectrum, the leucophores will reflect green and blue, helping make the octopus look sort of invisible.

But wait, it gets even more complicated, because some octopuses can also change the texture of the skin. Sometimes that just means it can make its skin bumpy to help it blend in with rocks or coral, but some species can change the shape of the skin more drastically.

We still don’t fully understand how cephalopods know what colors they should change to. While octopuses mostly have good eyesight, at least some species are colorblind. But they can still match the background colors exactly. Some preliminary research into cuttlefish skin appears to show that the cuttlefish has a type of photosensor in the skin that allows it to sense light wavelengths and brightness without needing to use its eyes. Basically the skin acts like its own eye. This is getting weirder and weirder, but that happens when we talk about cephalopods because they are peculiar and fascinating animals. In 2019, marine biologists released footage of a captive octopus changing colors in her sleep. Some researchers think she may have been dreaming, and her dream prompted the color changes.

Let’s get back to the mimic octopus now that we’ve learned the basics of how octopuses change color. The mimic octopus lives throughout much of the Indo-Pacific, especially around Indonesia, and has an armspan of about two feet across, or 60 cm. It generally lives in shallow, murky water, where it forages for small crustaceans and occasionally catches small fish. It’s usually light brown with darker brown stripes, but it’s good at changing both its color and its shape to mimic other animals.

So far, researchers have documented it mimicking 15 other animals, including a sea snake where it hides all but two of its legs, a lion fish where it holds its legs out to look like spines, jellyfish, sting rays, frogfish, starfish, sponges, tube-worms, flatfish, and even a crab. It actually imitates a crab in order to approach other crabs, which it then grabs and eats. So obviously it’s not using its mimicry ability randomly. It will imitate a sea snake if it feels threatened by an animal that is eaten by sea snakes, for instance. And it was only discovered in 1998 and hasn’t been studied very well yet.

Unfortunately, the mimic octopus is rare to start with and threatened by pollution and habitat loss. Once it was discovered, people immediately wanted to own them. But the mimic octopus doesn’t do well in captivity, usually dying within weeks or even days. Even octopus experts have trouble keeping them alive for very long. One expert reported that the mimic octopus is incredibly shy and spends most of its time hiding deep under the sand. It’s mostly active at night and doesn’t like bright light. It’s incredibly sensitive to temperature changes, water quality, and even the type of salt used in saltwater aquariums, and most importantly, he reported that in captivity, it doesn’t do any imitating.

Chameleons are also famous for their ability to change color and pattern, but not every species can do so. The ones who can use a very different process for color changing compared to octopuses. The chameleon has a layer of skin that contains pigments with a layer beneath that contains crystals of guanine, a reflective molecule that’s used in cosmetics to make things look shimmery, like nail polish. The chameleon can move the crystals to change the way light reflects off them, which affects the color, especially when combined with the pigments in the upper layer of skin. The color change takes about 20 seconds and different species are able to change into different colors and patterns.

Not all mimics use appearance. A number of moths are toxic to bats, but it’s no use evolving bright colors to advertise their toxicity to predators who use echolocation to hunt. Instead, the moths generate high-pitched clicks that the bats hear, recognize, and avoid. And naturally, some non-toxic moths also generate the same sounds to mimic the toxic moths.

Let’s finish with a tiny spider that also changes color. It’s called the white crab spider or the goldenrod crab spider or the banana crab spider, or just the flower spider. It’s a small, common spider that lives throughout the northern hemisphere. You’ve probably seen a few of them in your time, probably when you’re leaning down to sniff a flower. It hangs out on flowers and can be white or yellow in color. A big female can be 10 mm long, not counting her legs, while males are barely half that size. They’re called crab spiders because they often run sideways like a crab. The flower spider doesn’t build a web. Instead, it just sits on a flower.

The male flower spider climbs around from flower to flower, looking for a mate. The female generally stays put on a particular flower until it fades, and then she’ll find a new one. If she moves from a yellow flower to a white one, or vice versa, she can change color to match, but it’s not a quick process. It takes at least ten days and sometimes up to 25 days to change from white to yellow, since the spider has to secrete yellow pigment into its cells, while changing from yellow to white usually takes less than a week. If she’s on a flower that is another color, she’ll usually remain white. Only the female can change color, and some females may have small red or pink markings that don’t change color. The male is usually yellow or off-white in color.

The flower spider is so well camouflaged that it can be hard to spot even if you’re looking for it. It eats butterflies and moths, bees, and other insects that visit the flowers. Males will also eat pollen. Its venom is especially toxic to bees, although it’s harmless to humans. It really likes to eat bumblebees. Its first pair of legs are longest and curve forward to make it easier for the spider to grab a bumblebee and sink its fangs into it. Meanwhile, the bumblebee has black and yellow stripes to advertise to potential predators that it will sting, but that doesn’t help it when it comes to the little crab spider. Danger in the bee world!

You can find Strange Animals Podcast online at strangeanimalspodcast.blubrry.net. That’s blueberry without any E’s. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. We also have a Patreon if you’d like to support us that way.

Don’t forget to contact me if you want to enter the book giveaway contest, which will run through October 31, 2020! If you want to enter, just let me know by any means you like.

Thanks for listening!

Episode 187: The Praying Mantis and the Cockroach

We finish off Invertebrate August in style, with great suggestions from Rosy and Kim!

Also, I was a guest on The Flopcast last week if you want to hear me talking about DragonCon and birding with my friend Kevin! Also, he actually has a few pictures of me if you want to know what I look like (I hate having my picture taken).

Further Reading:

Why Do Mantids Only Have One Ear?

Secrets of the orchid mantis revealed

In this new praying mantis group, gender dictates disguise

Male (left) and female (right) Hondurantemna chespiritoi (photos from article linked to just above):

The female Hondurantemna chespiritoi showing her leaf-like wings:

An orchid mantis:

Vespamantoida wherleyi looks like a wasp:

A Neotropical bark mantis, hiding in plain sight:

The Indian domino cockroach is actually kind of cute:


Show Transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.

It’s the last week of Invertebrate August, but what a wild ride it’s been. We’ll round out the month with a few more listener suggestions, so thanks to Kim and Rosy for some awesome topics!

Before we get started, though, last week I was a guest on The Flopcast, a hilarious and family-friendly podcast about geeky stuff like old cartoons and TV shows and music from when you were a kid, unless you’re a kid now in which case music from before you were born. I talked with the host Kevin about DragonCon, so if you are interested in hearing me talk about something besides animals, I’ll put a link in the show notes so you can go listen!

But now, on to the invertebrates! First, let’s learn about the mantis, also called the praying mantis, which is Rosy’s suggestion. If you play Animal Crossing you’ll be familiar with the orchid mantis, but there are lots of species. Lots. Like, almost 2,500 species. They live throughout much of the world but are most common in tropical areas.

All mantises have elongated bodies, enlarged forelegs used for catching and holding prey, and a triangular head with big eyes. The mantis walks on its two rear pairs of legs but holds its big front legs up to use as weapons. Most species have wings and can fly, some don’t, but they are all predators. Most are ambush predators who wait for an insect or other small animal to come near, then grab it with their spiny front legs. Mantises have good vision since they primarily hunt by sight. They’re also most active during the day.

The mantis will eat, in no particular order, insects, frogs and other amphibians, lizards, snakes, small turtles, mice, small birds, spiders, other mantises, and fish. That’s right, fish. In 2017 a team researching insects in India observed a mantis catching guppies in a rooftop garden pond. To reach the guppies, it walked across the water-lilies growing on the water. The scientists observed the mantis catch and eat nine guppies over the course of several nights, and surprisingly, it hunted them in the evening and night when mantises aren’t usually active.

Mantises can and will catch and eat hummingbirds by climbing onto hummingbird feeders or into flowering bushes, and when a hummingbird comes to feed, chomp! So basically, mantises will eat anything they can catch, and they can catch a lot of things.

The eyesight of mantises is interesting, and scientists are discovering more about it all the time. A study published in 2018 reports that the stereo vision, also called 3D vision, that mantises have is very different from that in humans. Whereas human vision is in 3D all the time, the mantis’s stereo vision only kicks in when there’s movement nearby. At that point the mantis has sharp details of exactly where potential prey is, since that’s what’s most important to it. The mantis is also the only insect known to have stereo vision at all.

The mantis doesn’t have any kind of hearing organ on its head and for a long time entomologists thought it was deaf. But it turns out that the mantis does have a type of ear that’s specialized for one thing. It’s not on the head, though. Many species of mantis have a single ear, or what’s called an auditory thoracic organ, in what is sort of their chest, just in front of the middle pair of legs. Technically the organ is split in two, but it acts as a single ear. The reason they have this organ is to detect bats. That’s right, bats. The ear can hear in the ultrasonic range. Some mantis species will fly to find new territory, especially males, and they do this mostly at night to avoid birds. But then they have to avoid bats. When a flying mantis hears a bat’s echolocation calls, it will go into a dramatic dive to avoid it, sometimes just plummeting to the ground.

Most mantises have evolved camouflage to hide from both predators and prey. Some look like leaves, like a newly discovered species from the Honduras and Mexico. Hondurantemna chespiritoi lives in forests and demonstrates sexual dimorphism, where the males and females look very different. The male is light brown with darker and lighter spots, and basically looks sort of like a bundle of sticks. He’s about two inches long, or 5 cm. The female is twice his size and bright green, with forewings that resemble leaves—so much so that the wings have spots that look like blemishes on a leaf and veins that resemble veins in a leaf. The wings are also big enough to hide the body.

Flower mantises, including the orchid mantis, are camouflaged to look like flowers. You probably guessed that from the name. The orchid mantis lives in tropical forests in parts of southeast Asia and is rare and beautiful. It looks so much like a flower that butterflies will land on it thinking it’s actually a flower, at which point—you know. CHOMP. It’s white and pink with heart-shaped lobes on its legs that resemble flower petals, and it mostly eats butterflies and bees. But scientists have determined that despite its name, the orchid mantis isn’t actually trying to specifically mimic an orchid. It doesn’t perfectly resemble any particular type of flower, but seems to have evolved to look like a general flower of the kind that insects just like.

Another newly discovered mantis species, Vespamantoida wherleyi, mimics a wasp. It was discovered in Peru near the Amazon River in 2013, and is bright orangey red in color with black markings and long antennae. Not only does it look like a wasp, it even walks and acts like a wasp. Since wasps are famous for their stinging abilities, many predators avoid them.

Other mantis species are camouflaged to look like tree bark, like the 19 new species of mantis described a few years ago that live in Central and South America. They’re called Neotropical bark mantises and unlike most mantis species, they actively pursue prey. They’re extremely fast runners as a result. They have flattened bodies and are mottled to look like pieces of bark, including imitation patches of moss and lichen. Another bark mantis group lives in Australia.

New species of mantis are discovered frequently, and some entomologists think only about half of the species alive today have actually been described scientifically. Many species that are described have barely been studied. So if you were thinking of going into entomology, praying mantises are a hot field.

The smallest species of mantis is Bolbe pygmea, which only grows to about 10 mm long. It lives in Australia. The largest species is probably the Chinese mantis, which grows almost 4.5 inches long, or 11 cm. It’s native to China and other parts of Asia, but has been introduced into North America.

The female mantis lays her eggs inside a ball of froth that then hardens to make a protective shell called an ootheca [oh-a-THEK-a]. Depending on the species, the ootheca may be attached to a tree or other plant, or may just lie on the ground. In some species, the female guards her eggs by standing over the ootheca and attacking anything that comes too close. Baby mantises are called nymphs.

At least one species of mantis doesn’t have any males, just females. The females produce eggs that hatch even though they’ve never been fertilized, which is called parthenogenesis. A few other species of mantis can reproduce parthenogenetically if they can’t find a male.

That brings us to the one thing that most people know about the praying mantis, that the female cannibalizes the male after or even during mating. This does happen in some species, but not always. It tends to happen more when the female is hungry or poorly nourished, but males are typically cautious about approaching a hungry female. But yes, sometimes the female does just bite the male’s head off, literally, while the pair is in the process of mating.

The praying mantis gets its name because of the way it holds its front legs up. It sort of looks like someone saying a prayer. In this case, the prayer is probably, “Please let me find a big juicy bug to eat.”

The mantis is closely related to the cockroach, which is perfect because Kim suggested roaches as a topic! There are even more cockroach species than there are mantis species, which is saying a lot—at least 4,600 known. Of those, only about 30 are ones that want to live in your house and only six of those 30 are major pests.

A few cockroach species are actually pretty, like the Indian domino cockroach from southern India. It’s a rounded insect that lives in leaf litter in forests and eats decomposing plant material. It grows about 1.5 inches long, or 3.5 cm, although males are smaller. It’s black with seven big white spots.

Generally, though, cockroaches are nothing special to look at. Most species are plain brown with a small head, a flattened body, and wings, although not all species can fly. Most are omnivorous and nocturnal, and many are social insects that live in colonies. They’re also extremely tough. They can go a month without eating at all and some species can even survive up to 45 minutes without air.

Cockroach pests will eat human food, pet food, leather, shed hairs, skin flakes they find in dirty clothes, paper, glue, and book bindings. They can spread diseases like salmonella, although fortunately it’s not very common. Cockroach feces can cause asthmatic reactions in some people, though, and can make your home smell bad.

Cockroaches can also become resistant to pesticides. One effective way to rid your home of roaches is to release a whole bunch of praying mantis nymphs inside. The nymphs will eat each other as well as cockroach nymphs, and once the surviving mantises are adults they will happily eat up all the full-grown and young roaches they can find. Of course then you’ve got mantises in your house, but mantises don’t spread diseases that humans can catch, and of course you can name them and treat them as pets. Some people keep mantises as pets anyway.

Speaking of which, some people keep the Indian domino cockroach as a pet. Some other people keep the hissing cockroach as a pet. The hissing cockroach is native to Madagascar and mostly lives in rotting logs, where it eats rotting plant material. There are actually 20 known species and they differ from other cockroaches because they don’t have wings. Also, they make horrible noises. The hissing is a method of communication and includes different hisses to warn other roaches when a predator approaches, or to establish dominance, or to attract a mate. The largest species can grow up to 3 inches long, or 7.5 cm.

This is what a hissing cockroach sounds like.

[hissing cockroach]

You can find Strange Animals Podcast online at strangeanimalspodcast.blubrry.net. That’s blueberry without any E’s. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. If you like the podcast and want to help us out, leave us a rating and review on Apple Podcasts or just tell a friend. We also have a Patreon at patreon.com/strangeanimalspodcast if you’d like to support us that way.

Thanks for listening!