Question: Are Shrimp and Cockroaches Related? Hmm…
The idea of a big fat cockroach topping off your fancy shrimp cocktail probably grosses you out.
And it should. Creepy crawly cockroaches anywhere near our food is definitely a big no-no. But you might be surprised to learn how closely related shrimp and cockroaches are!
All plants and animals are organized by scientists into separate groups based on the things they have in common. An easy example is how tigers and lions are very closely related, while cheetahs are basically cousins of them both. Your house cat Fluffy is related to all three, but more closely to a cheetah than a lion. They all eat meat, are mammals, and have quick reflexes and sharp teeth.
What about cockroaches? Do they have anything in common with shrimp?
As a matter of fact they do, and this is why it’s so important to understand how scientists group things. Cockroaches are insects. And shrimp are crustaceans. And while they both belong to their own groups (insects and crustaceans), they also share characteristics that group them together.
What are those characteristics?
Both insects and crustaceans have three part bodies, made up of a head, thorax, and abdomen.
Both have jointed legs.
And both have exoskeletons. An exoskeleton means that their bodies’ “bones” are on the outside instead of the inside (like yours). If you’ve ever eaten steamed shrimp, you probably know that they have a hard shell you have to take off first. This is the shrimp’s exoskeleton, and insects such as cockroaches have them too.
Creatures that share these characteristics belong to a group called Arthropods, which also include animals like spiders and centipedes. Scientists have found that insects and crustaceans have a particularly close evolutionary relationship, though. So close that they belong to a group all their own called Pancrustacea.
That means that shrimp, lobsters, and other crustaceans are related – very closely related – not only to cockroaches, but to all other insects, too.
Food for thought: If shrimp lived on land, would we change our opinion of them?
So what about the fact that people scream when they see a cockroach on the table, but not when they see a shrimp salad? Well, aside from the fact that in Thailand and some other Asian countries people do eat cockroaches as a delicacy, the ones here are dirty and sometimes carry disease.
So while the relationship is close, a shrimp is definitely not a cockroach. And though Pancrustacea sounds like the most delicious menu item ever, you’ll want to stay very choosy about the kind of Arthropod you eat.
Cockroaches are insects that go through a gradual metamorphosis. Like mayflies, cicadas, and aphids that also mature this way, they go through three developmental stages: egg, nymph, and adult. Charting the cockroach life cycle is useful for understanding gradual metamorphosis and for learning about them as pests.
In this collection of “How-to-draw” sheets, elementary kids and middle schoolers can draw semi-realistic looking cockroach eggs and cockroach nymphs for biology projects and presentations. The sheets are free, printable, and can be downloaded individually or in a single document here.
The Cockroach Egg
Cockroaches do lay eggs, but unless you get out a scalpel, you’ll never see them. That’s because the female lays an egg case (known as an ootheca) that holds all of the eggs inside. The ootheca is made of a tough material that protects the eggs from harm. Depending on the kind of cockroach, an ootheca can hold as few as 14 eggs and as many as 50, which incubate anywhere from 24 to 215 days.
When the eggs inside the ootheca hatch, the young cockroaches inside begin to take gulps of air, expanding their bodies and eventually spreading the ootheca apart like a purse, allowing them to escape. As they slip out, they shed the membrane that covered them inside the egg.
At maturity, adult cockroaches will be able to mate and reproduce, and the adults of some species will have wings. An adult female can produce as many as 4,500 offspring during her lifetime. Cockroaches have lifespans of between 200 and 700 days based on their species and sex, with an average lifespan of about one year.
Sure, house cockroaches are dirty, smelly, and not exactly the sort of creature you want to see on your kitchen counter.
But are they fast?
You bet they’re fast. Superhero fast. So fast that cockroaches are considered one of the fastest insects on the planet.
With lots of interest in the creatures, scientists couldn’t resist finding out exactly how fast they really are. So they began by testing cockroach’s “start-speed,” the time it takes to start moving from a dead stop.
For even the fastest of humans, start-speed doesn’t go much lower than about 110 milliseconds (about 1/10th of a second). But cockroaches went much faster, darting off at 8.2 milliseconds. Literally faster than the blink of an eye.
At top speed, they’re remarkably fast, and can cover 50 body lengths in a single second. For animals the size of humans that would be the equivalent of 200 miles an hour!
So how do cockroaches run that fast? The secret is in their legs. All six legs have three knees, 18 knees altogether. With so many joints, their movement has precision and accuracy, with very little wasted movement that could slow them down. Once they get up to speed, they rise on their hind legs and run as humans do, which helps them run even faster.
It’s those legs that help them react so fast too. Each leg has tiny hairs that can detect even the slightest movement of air. When you walk into a room, a cockroach can sense the air stirring… and off it goes!
They’re legs have another important feature. A hook-like structure that allows them to flip under ledges or scramble under tables at warp speed. The scientists studying these special ops-style stunts found that the acrobatics happen so fast, the cameras had to slowed down to super-slow speeds to track them all.
So it looks like when it comes to speed, the common house cockroach may not be so common after all!
How long can a cockroach live without its head? A lot longer than you or I could, that’s for sure.
Of the many curious facts about this highly-studied creature, its ability to live without a head… for a while anyway… has got to be one of the creepiest.
But before outright telling you how long a cockroach can survive without a head, let’s look at the science behind why it’s possible at all. Because there’s something remarkable about a creature that can scoot across your kitchen floor, even when it’s missing its noggin.
A Headless Cockroach Isn’t Going to Bleed to Death From Its Wound
Even for major catastrophes like losing a head, cockroaches don’t bleed very much. Unlike humans, they have an open circulatory system: A system for distributing blood through their bodies that doesn’t depend on a closed network of arteries and veins. Their blood doesn’t pump under pressure like ours, but just sort of sloshes around, making its way into the cockroach’s tissues.
The great thing about this system – if you’re someday going to be headless – is that when a major wound occurs, blood doesn’t suddenly get forced out. For a cockroach that loses its head, the blood just clots at the neck. The cockroach will have a nasty scab for sure (where its head used to be), but it won’t die from loss of blood.
A Headless Cockroach Isn’t Going to Suffocate
Unlike humans, cockroaches don’t breath through a nose or their mouth. Instead they breathe through small holes in their bodies called spiracles that don’t need a brain to direct them. No nose, no mouth, and no need for a brain to regulate your breathing means that you can breathe all you want to without a head.
So that’s a second hurdle that won’t stop a cockroach. It won’t suffocate from its catastrophe.
A Headless Cockroach Can Get By Without a Brain
Cockroaches do in fact have brains. And they use them. It’s just that cockroaches don’t really need them that much.
In addition to brains, they have nerve tissues that control reflexes throughout their bodies, and these are distributed within each body segment. If a cockroach loses its head and brain, the nerve tissues (known as nerve tissue agglomerations) continue doing their job, providing the strange headless creature a fairly normal life. It can stand, react to touch, and move around.
In fact, aside from looking like something out of a horror movie or your worst nightmare, a headless cockroach behaves a lot any other cockroach. And it would continue its headless existence except for one thing…
A Headless Cockroach Can’t Eat or Drink
A headless cockroach isn’t going to die from bleeding and it’s not going to die from being unable to breathe. It’s also not going to die from the relatively minor event (for it) of losing its brain.
But it is going to die from being unable to eat. And well before that, it’s going to die from thirst. A headless cockroach has no mouth to drink with and will be dead from dehydration in less than a week.
Which brings the total day count from the moment it loses its head to the moment it loses its life to somewhere around 7 days or less. Not exactly a lot. But a lot more than you or I could manage to do.
Thought this was fun? You’re probably also wondering, “Are there cockroaches in chocolate?”
The short answer? Yes they do. Cockroaches don’t discriminate when it comes to biting things, including lots of things in your home. Do cockroaches bite humans? In a word, yes.
But also… not very often.
Unlike fleas, ticks, and bed bugs that bite humans for survival, cockroaches aren’t actually out looking for a feast of human blood. They’re just scavenging and well – there you are. Sleeping so peacefully with your foot out of the covers.
Roaches really don’t go after humans in general, and roach bites on humans happen very infrequently. If you did get a cockroach bite, it was probably just taking a nibble to see if you consist of the food they like. When roaches encounter humans, they’re seldom out to bite you, and just move on to tastier treats most of the time.
But that doesn’t mean roach bites are okay. They’re not. More about that shortly.
What Does a Cockroach Bite Look Like?
What does a cockroach bite look like? Like other insect bites, mostly. A cockroach bite mark is going to look similar to a mosquito bite. It will probably itch and you may see some swelling.
Does it hurt when you’re bitten? Possibly. Possibly not. Though cockroaches have extremely strong jaws that can chomp down with a force fifty times their own weight, some people don’t feel them at all. Others who do say they feel like an ant bite. It probably has to do with the size of the roach.
That’s roach bites on humans. But do roaches bite pets?
Yes, they can bite pets too. But they’re even less likely to bite pets than humans though because pets are typically seen as predators by roaches. Those rare cockroach bites that do occur to pets aren’t visible because of fur, but are uncomfortable and itchy, so if they happened, you might see pets visibly scratching.
Which Type of Cockroaches Bite?
Another short answer: They all do. But none of them bite very much. There are 4,500 species of cockroach in the world, thirty of which are known pests. Of those 30 species, you’re only likely to encounter five in the U.S. that might take a nibble of you:
The German Cockroach. The German cockroach is one of the most common cockroaches and biggest pest problem globally. You can distinguish them by their size (they’re small), the two dark stripes on their backs, and their light brown color. Sugar and starches are preferred food sources, but like all cockroaches, they’re scavengers and don’t shy away from proteins. Do German cockroaches bite? They can, but it’s unlikely to happen to you.
The American Cockroach. The American cockroach, sometimes referred to as the palmetto bug, is a larger species of cockroach that can grow up to three inches in length. Doubling the survival rate of most roaches, it lives up to two years. It’s either dark reddish in color or brown with yellow edges across its shell. It feeds on fermented organic matter or dead animals, but will eat lots of other things you wouldn’t believe. It’s possible to get a palmetto bug bite, but rare.
The Oriental Cockroach. Sometimes mistaken for water bugs, Oriental cockroaches are winged but can’t fly and grow to one and a quarter inches in length. You can tell them apart by their dark brown or black color and distinctive shape. Do Oriental cockroaches bite? Sometimes, yes. But not very often.
The Brown Banded Cockroach. Smaller than an Oriental or American roach, the Brown Banded cockroach measures just half an inch in length. They tend to flock to warm, dry areas. Males can fly, but more often leap. They’re golden and dark brown colored, although females have a reddish cast. Like other roaches, they’ll occasionally but rarely bite.
The Smoky Brown Cockroach. This species relies on moisture to live. (A dehumidifier might be a weapon of choice.) Smoky brown cockroaches are about one and a half inches long. They are good flyers, for roaches. A dark brown shell and body distinguish this roach. Does it bite? Rarely, but yes.
So can cockroaches bite? Yes. All of them can bite. Do cockroaches bite? Yes, but not very often. At least not to you and me. And though it’s possible that bite on your foot is a cockroach bite, it’s far more likely to have come from a mosquito or spider.
Treating Cockroach Bites
Cockroach bite treatment is the same as other bug bite treatments. Use soap and warm water to clean the area. Then sterilize it with alcohol or another disinfectant. Bites can be treated with ice to reduce swelling and by applying anti-itch cream. Also possibly soothing for cockroach bite first aid would be tea tree oil, lemon juice, aloe vera, or a moist tea bag placed over the wound.
Try not to scratch. If you have an allergic reaction to a roach bite, it may need medical treatment.
Preventing Cockroach Bites
Though cockroach bites can (though rarely) occur, the greater danger has to do with what seeing cockroaches in your home means. If it means you have an infestation, coming into contact with that infestation has the potential to make you sick.
Cockroaches can be disseminators of salmonella, streptococcus, staphylococcus, cholera, dysentery, escherichia coli, poliomyelitis virus, giardia, listeriosis, and gastroenteritis. They can make your allergies worse, and if you have asthma, can increase your risk of an attack.
How to prevent cockroach bites and the risk of disease too? Once it’s clear that cockroaches have invaded your home (and if you actually have cockroach bites, it’s a pretty scary sign), you’ll need to take action as soon as possible, eliminating the pests and cleaning up the signs of infestation that remain.