Few insects can make people squirm like the much-maligned cockroach. Just the thought of one of these shiny-backed insects skittering across a floor or, worse, countertop late at night is enough to give even the most stalwart individual the heebiejeebies. And their longstanding reputation as being the only creature able to withstand nuclear war doesn’t help make them any more “cuddly.” After all, who likes to think of humans being replaced by hordes of crawling cockroaches?
However, as with other types of reviled insects, their reputation as being “dirty” and disreputable is pretty much solely due to the human perspective on just a handful of species and a basic but broad misunderstanding of roaches and their real “purpose” as members of the world’s vast ecosystem.
There are about 4,500 species of cockroaches worldwide, but only a handful prefer taking up residence with humans. Of those, only four species make the “most wanted” list for most homeowners: the American, the German, the Oriental and the brown-banded cockroach. While the German species is more common than the other three, the American is larger and, therefore, more likely to cause fear and disgust when it scrambles across your floor or flies into your face. But of all four, the Oriental cockroach is the most problematic; that’s because it loves living in sewers, and that means when it comes in contact with humans in their homes or elsewhere, it’s much more likely to spread diseases.
And speaking of disease, cockroaches actually can pass diseases that cause food poisoning and other digestive tract disorders, usually through their saliva or their feces, which they tend to deposit on a regular basis throughout their domains, using the scent to form trails that can help them get from one place to another. Their feces and saliva may also be able to pass other types of diseases, including hepatitis or even polio.
But beyond these four species, by and large cockroaches keep to themselves, living primarily in warm, moist regions and feeding on decaying wood, leaf debris and other matter, turning it into nutrient-rich soil that in turn fosters a healthier environment overall. Plus, they’re a great food source for plenty of other insects as well as birds, small mammals, reptiles and amphibians.
Roaches may have a dastardly reputation in the human world, but in the insect world, they have a pretty great rep as parents. In fact, studies have found cockroaches to be among the most caring of all insect parents, with some species caring for their young for years. (Others, it must be said, simply drop the egg sac and run.)
Life for a cockroach begins in an egg sac or capsule that contains dozens of its brothers and sisters. Eggs sacs are fertilized by sperm from the male cockroach, and many females carry the fertilized capsules on the outside of their bodies – typically the underside. The time it takes for the fertilized capsule to hatch can range anywhere from one to three months or so. Once the capsule hatches, the tiny newborn roaches emerge, usually looking a lot like their full-grown parents. But there is one significant difference: Their outer shells are still soft, making them much more prone to predation. This is when many species of parent roaches are especially protective, and some roaches even dig small burrows for the egg sacs to provide a place for the “babies” to chill while they complete their development. A few wood-eating species can care for their young for a prolonged period of time, seeing them through several stages of molting until their hard exoskeletons finish forming.
While the young are being cared for by the parents – the brooding period – the mother renders another kindly service beyond physical protection: She feeds the neonates some of her fecal matter to transfer important gut bacteria that can help keep them healthy throughout their lifecycles. Some species offer an alternate “menu” item – a gelatinous mass expelled by the mother and offering similar health benefits for the young that consume it.
Once grown, the cockroaches spend most of their adult lives searching for food, eating and reproducing. And that brings us to another reason why roaches have been able to survive for so long and in so many places: They’ll eat nearly anything, from debris found on the forest floor to paper products and books to crumbs and garbage, making it very easy to adapt – and thrive – in nearly any environment.
While some cockroach species may be more or less independent, most roaches prefer the company of other roaches and the benefits of a more organized society. For instance, both German and American cockroaches are extremely social, enjoying a common shelter, hunting and foraging together, transferring information from one colony member to another, and even recognizing their kin, with multiple generations living together under the same “roof.” In fact, cockroaches that don’t enjoy such social interaction and companionship suffer, taking longer to molt and transform into adults and finding it much more difficult to find a mate in later life.
Despite their community involvement and dependence, the average daily – or rather, nightly – routine of a cockroach is one of relative independence. After spending the daylight hours resting, sleeping and communing, roaches head out individually at night to seek out food, leaving trails of hormones and other substances that communicate the location of their finds.
And these special chemicals play another important role: They can help cockroaches identify which other members of the colony are relatives, and even determine how closely they’re related. Scientists say this ability prevents roaches from mating with their siblings, helping to enable the colony to stay healthy and survive.
While they may not be as socially developed as, say, ants or similar bugs that have clearly defined roles for different community members, cockroaches are capable of making group decisions. For instance, while foraging, cockroaches use their scent trails to locate potential new places to hang out. When the group becomes too large to remain in their current location, they decide, as a group, which of these potential new locations constitutes the best choice. By working together as a group, decisions can be made more quickly and disputes can be avoided. And unlike highly socialized ants where only the queen is allowed to mate, cockroach communities are much more democratic, allowing any member of the colony to reproduce.
Of course, group behavior does involve some amount of peer pressure, and that’s not always a good thing. In one recent study, researchers created a tiny robot designed to excrete cockroach scent trails, leading masses of cockroaches away from their secured dens in a sort of Pied Piper-esque experiment that could have future implications for pest control.
That’s not the only odd study involving cockroaches. Researchers from Japan decided to conduct an experiment to learn if cockroaches are subject to conditioned responses like those demonstrated the famous dog studies conducted by Russian physiologist Ivan Pavlov. In those studies, dogs were fed every time a bell was rung. Eventually, the dogs became trained to salivate every time they heard a bell, regardless of whether or not food was presented. In the cockroach version, the researchers placed a tiny droplet of sugar water (roaches, like humans, are particularly fond of sweets) in the roaches’ mouths, then stimulated their antennae with peppermint scent. After repeating the exposures a few times, the researchers found the scent alone was enough to cause the roaches to, well, salivate.
Sure, pretty much no one outside of a scientist actually wants to see a cockroach. But thanks to the generally skeevy reaction most people have when the subject of roaches is brought up, it can be pretty fun to talk about them. Here are just a few “fun facts” to freak out your most squeamish friends and loved ones:
So what of that rumor about nuclear survival? Is it true? And how did roaches gain that rep in the first place? It all started following the World War II bombings of Hiroshima and Nagasaki, where roaches were the only living things left behind in the cities’ rubble. More recently, the intrepid team of the Discovery Channel’s Mythbuster’s program tested the nuclear survival claim by exposing roach colonies to varying degrees of radiation, from 1,000 rads (enough to kill a human in about 10 minutes) all the way to 100,000 rads, then tracking their mortality rates for a month. While about half of the roaches survived the lower dose with ease, the 100,000-rad exposure proved completely lethal. However, at 10,000 rads – about the same amount of exposure caused by the World War II bombs – about 10 percent survived.
Yes, cockroaches may elicit some creepy reactions from most of us. But when it comes down to it, they’re pretty remarkable insects, forming vast societies and intelligent communities that have helped them survive for more than 300 million years. Of course, no one is going to blame you for stomping a roach that’s careening across your kitchen floor in the dead of night. But it is nice to know that as repugnant as we may find them to be in our own homes, they play an integral and essential role in the world at large.