Melissa Kaplan's
Herp Care Collection
Last updated January 1, 2014

Hissing Cockroaches: The Battletanks of the Cockroach World

Robert Gale Breene III, PhD, College of the Southwest, Carlsbad, New Mexico USA

It happened while I was visiting a woman friend of mine and her seven-year-old son years ago in College Station, Texas. I was out in the garden while she was fussing around in the kitchen. The silence of the peaceful garden was abruptly shattered by piercing, blood-curdling screams!

I sprinted for the door with horrible visions of gore and mutilated bodies running rampant through my mind. Whipping through the entrance into the house, I found the woman and her son standing on separate chairs, howling their lungs out in sheer terror and pointing vigorously at a rather smug-looking American cockroach sauntering along the floor in front of them. I picked the critter up and put it outside; not an easy task considering I was laughing so hard that tears were streaming down my face and I could hardly breathe. If that's how you feel about cockroaches, then you may want to stop reading now.

Cockroaches, often incorrectly called waterbugs or roaches (a roach is a kind of European fish) go way back, not having changed in any obvious manner for some 320 million years. Their closest relatives are termites. This is not surprising because cockroaches are part of the decomposer component of the ecosystem (recyclers, as are termites) which normally eat decaying organic material, helping to break it down into simpler compounds for re-use by plants. A few cockroach species actually eat wood. Only a few of the 4,000 or so species of cockroaches (order Blattaria) are known to pester humans. Most stay out of sight and out of mind busily doing their important job in the ecosystem.

The hissing cockroach, Gromphadorhina portentosa, is one of the larger species of cockroaches, and hails from forested areas of Madagascar. Its exoskeleton or "skin" is thick and hardened, inspiring one author to call it "the battle tank of the cockroach world." Hissing cockroaches can get quite large. Some can reach nearly three inches in length, although two, perhaps two and a half inches is more common. Some have said that a six and a half inch hissing cockroach was found in the wild, but this is probably the kind of story I hear so many times about tarantulas: A four inch legspan tarantula is transformed into the size of a large dinner plate after the story is retold a sufficient number of times (fish tales, the big one that got away).

Anatomy, Morphology
Hissing cockroaches have the typical insect body setup. They have three major body regions: The head, thorax, and abdomen. The head (the most disputed region) has from three to seven segments (depending on what authority you are talking to and how loud they are speaking). A pair of long antennae, a pair of mandibles for chewing food, a pair of compound eyes, and other essential components are located on the head, as you may have expected. In captivity, the antennae often partly or completely break off. This doesn't seem to have much of a negative effect. The head is almost completed covered from above by the pronotum (this is the top part of the prothorax).

The prothorax is the first of three thoracic segments. The other two are the mesothorax (in the middle), and the metathorax. Each thoracic segment has a pair of walking legs. The legs have lots of sharp spines on them, and can prick people with soft skin, although I've never heard of them being able to draw blood. When handled, hissers often rapidly latch onto your fingers and hang on for dear life. Needless to say, this can startle some people, especially if they also start hissing.

Hissing cockroaches don't have wings as adults. Scientists call this secondarily wingless, since they had them at one time long ago, but apparently had no use for them, so they were discontinued, so to speak. Many cave dwelling species of animals have lost their eyes due to the same reason.

The abdomen consists of eleven or so segments, although only eight or nine are visible. The abdomen contains the sexual organs, the heart (on the top, or dorsal side of the insect) which is a tube that pumps blood forward from the abdomen through the aorta (a large artery) and dumps it into the head. The abdomen also contains many other organs.

Internally, insects don't have lots of arteries and veins, but have what's called an open blood bath (hemocoel). The blood carries nutrients around and serves other functions. Unlike humans, the blood plays a very small role in respiration (bringing in oxygen and getting rid of carbon monoxide). In fact, in a few insects, when they start to walk, the heart shuts off because just the motion of walking provides all the blood circulation the insect needs. When they stop, the heart starts up again.

As with most insects, cockroaches breathe (respire) using air tubes connected to openings (spiracles) on the outside of the insect body. The spiracles can open and close in most species. These air tubes lead to all the tissues in the body (heart, ovaries, others) that need oxygen and supply them with it. The spiracles are what gave the hissing cockroach its fame. They hiss by forcefully expelling air out of the second pair of spiracles on the abdomen. Maybe, in a few million years, they'll learn how to whistle instead of just hiss.

The Sexes
Although a male in a particular colony may grow slightly longer than any of the females, in most colonies, the adult females are longer and a bit fatter than the males. Males have very obvious protruding frontal "horns" on the pronotum behind the head. Females also have these horns, but they are much less pronounced. Almost anyone can become an adult hissing cockroach sexing expert after very little time around them.

Overall, males are darker than females. Often, the entire top side of the males are jet black. The females usually have black pronotums, but a brown color begins to appear following that segment. Otherwise, males and females are various grades of medium to dark brown. Looking closely, you can see that the males have somewhat thicker antennae than females. Both sexes can hiss, but the males are more inclined to do it. Sometimes it seems that the most difficult time to get one to hiss is when I'm standing in front of a roomful of kids in an elementary school, with all of them eagerly waiting for the little beast to "talk."

In nature, hissing cockroaches are said to live together in hollow logs, often in large numbers. Some believe this may account for the male dominance behavior that occurs in the species, and that sound has replaced pheromones for species recognition and mating.

Many a night, I've listened to the males in my colony getting rowdy, hissing, and thrashing it out among themselves. The male with most heroic courage (usually the largest) gets the lion's share of the females. When two males encounter each other, they begin an animated sword fight using their antennae. After that, they use their most intimidating hiss, hunker down, and rush each other, frontal horns first. They keep crashing into each other (which can sometimes be heard) until one weakens and is driven back. This is followed by the winner "celebrating" by slapping his abdomen against the ground or against the "cowed" body of the vanquished male. The loser may then be chased around the cage by the winner for a while for good measure. The triumphant male is thought to win the privilege of gaining the most access to the females.

Mating
Mating is almost as spectacular as the males' fight for dominance. When the male first encounters a receptive female, the two begin the antennae sword fighting, but the violence is not there. The female begins to touch the male lightly with her antennae. This encourages the male to begin strutting around the female in a circle, hissing and also touching her lightly with his antennae. Shortly after, the male extends and lowers his abdomen, trying to back into her from behind. This is different than the mating act of any other cockroach currently known.

At the instant when the male pushes back and connects with the female, he emits an extraordinary series of hisses. A couple of researchers found that this made the female place her abdomen in a position permitting easy coupling. When the researchers muted males by stopping up the second pair of abdominal spiracles (that make the hissing noise), they found that mating was not successful. They recorded the male sounds, and found a muted male could successfully mate when they played the recorded sounds back at the right moment.

Instead of making ootheca (like an eggcase of sorts) hissing cockroaches give live birth. The females form the ootheca internally. When the eggs mature, the nymph exits the female through the genital opening. This doesn't happen all at once, but gradually. For one ootheca, a total of 20 to 50 nymphs per female are produced. Occasionally, a yellowish ootheca can be seen being ejected from the female. This is thought to be an aborted ootheca that was not viable for some reason.

Because of the tough, non-flexible properties of parts of the exoskeleton ("skin"), the nymphs need to molt to grow. Before a molt, they begin to digest the softer parts of their exoskeleton inside. When this is complete, the nymphs shed the remaining exoskeleton. Once the molt is complete, they are soft and bright white in color. They'll expand, harden, and darken within a few hours to a day or two.

Once adult, they're not known to molt again. The lifespan of the adults is not known as far as I know, but is suspected of being about one to three or more years.

Cages
The kind of a cage used to raise a single hissing cockroach, or an entire colony, depends on the needs and desires of the cockroach keeper. Many people want some kind of a substrate and glass or see-through plastic to observe the cockroach. Since the species lives in darkened hollow logs, this may cause stress problems ranging from reducing the life spans, to fertility problems.

I keep my colony in a large, 20 gallon (or larger) Rubbermaid (r) container with no substrate of any kind. I supply them with cardboard egg cartons and paper towel tubes. Water is best supplied (at least in larger colonies) by cutting a 12 oz. plastic cup down to about eight oz. Cut the cup precisely evenly, since a little space can lead to leakage that can flood the cage. Find a plastic one gallon jar lid, then take two paper towels placed together, fold them about two thirds of the way up, then fold from a different direction about a quarter of the way up. There should be about one third of an inch between the edge of the cup, centered in the jar lid, from the jar lid. The point is to allow the water to soak into the paper towel readily, without leakage. I know this sounds a little complex, but a little practice will help. Fill the plastic cup with water, place the folded paper towels into the one gallon plastic lid, put it on top of the water cup and invert it. Water should keep seeping out of the cup until the paper is wet, and then stop. Water is especially important for small nymphs, so don't let the water supply dry out.

I've found it's best to have a closely fitting top for the 20 gallon cage, which should be kept closed. About ten, small (half inch) holes should be drilled along the sides of the lid and sealed with microscreen. Too much ventilation is generally not good for an animal used to the often wet tropics. A two or three inch strip of Vaseline should be smeared about four or so inches below the top along the inside of the cage. This strip needs to be maintained to prevent malcontents from escaping.

Room temperature is usually fine for hissing cockroaches (75oF or higher). If you want faster growth and reproduction, higher temperatures are required. With each rise of 10oC, the metabolism doubles in insects. Keep them in the high 80s F, or even a bit higher. This will speed things up considerably. You need to watch the water supply very closely if you choose to keep them at higher temperatures.

Food
In nature, hissing cockroaches probably consume what ecologists call "decaying organic material." This means they'll thrive on nearly any material you give them, including fruits, vegetables, meat products. Feeding them rich and moist food of this variety is often not wise. These products can easily rot, producing fungal growth quickly. I've found dry chick mash, or inexpensive dry dog kibble will provide all of their nutritional needs. Some people have reported that some colonies seem to do quite well eating just cardboard. Perhaps they are wood feeders also, but if so, it's not known for certain as yet. For all we know, a substrate of paper towels and egg carton cardboard may be all the food they need.

In anecdotal discussions on fertility problems in the past, adding certain fats, such as a few drops of olive oil, has seemed to help.

Mites & Disease
Mites are nearly always present at one time or another with hissing cockroaches. Many people ignore them, since they don't appear to harm the cockroaches. If you're someone who raises hissing cockroaches to feed to your tarantulas, and there are many who do, you may need to fight the mites. There are two major ways.

The first is to wash off each cockroach under warm water then place them in a new cage. This is fine for people who don't keep many hissing cockroaches, but is next to impossible for very large colonies. The second major way is to purchase predator mites, generally sold as Hypoaspis sp., from a natural control beneficial insect and mite company. When the predators have cleaned out the nasty mite population, they'll die off themselves, usually completely.

Legal Issues
Hissing cockroaches do have a down side. When I lived in extreme South Texas a few years ago, a surprising story popped up in the local newspaper.

It seems a woman entered her home on South Padre Island and noticed a cockroach on her kitchen table. When she moved in closer for the kill, the cockroach hissed at her. She fainted and knocked her head on the kitchen counter, eventually requiring the paramedics to be called. Some person on South Padre Island had apparently released some hissing cockroaches.

Whether or not they can survive in semi-tropical areas such as South Padre Island, or parts of Florida, you should never release an exotic animal (in this case a nuisance) that can potentially establish itself away from its native habitat. If you produce more hissing cockroaches than you can handle, don't release them. Find another way. If nothing else, put them in the freezer overnight, then into the trash. This may seem cruel, but we don't need new potential exotic pests. Think about the Japanese beetle, starlings, Johnson grass, and so many more. Also, they may be illegal to own in your area. Check your city, county, and state regulations on them.

Hissing cockroaches can be great fun, but please be responsible with them.