In your yard: cockroaches

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You may have heard it said half-jokingly that cockroaches will still be on earth long after humans are extinct. There’s some truth to that. They’re amazingly adaptive and, according to fossil evidence, have been around for 300 million years, since the Carboniferous Period.

Cockroaches, also just called “roaches,” are incredibly hardy. They can hold their breath for up to 45 minutes, deliberately slow down their heart rate, withstand doses of radiation that would be lethal to humans and go without food for a month. They can run at close to three miles-per-hour and have reflexes so fast they can turn their body around in 1/25 of a second.

Besides all that, scientists have discovered that cockroaches have some surprisingly human characteristics: They’re very social (don’t we know that — if we see one, don’t we see many?). They recognize members of their own family and many generations of them live together. They have egalitarian social structures based on rules and can make group decisions. And, get this: Like some lonely humans, their health fails if they have to live alone.**

Okay, so cockroaches are survivors, and probably smarter than a grub, but so what? Well, like all other creatures on earth, they’re important in their own way: Not only are they an important food source for birds, frogs, lizard, snakes and mammals (including humans in some locales), they’re also essential recyclers of decomposing organic matter. What goes in their mouths comes out as enrichment for the soil. Those species that invade human structures are pests, to be sure, but others, which includes most of them, are beneficial. 

Cockroaches are usually associated with uncleanliness, especially if they find their way into a kitchen. However, lovers of cockroaches (yes, there many of them) beg to differ. They claim the cockroach’s bad rap is unfair, that, in reality, they routinely groom themselves to stay clean. The problem, it seems, is they aren’t picky about their food and will nibble on everything they come across, from tiny bits of spoiled meat to moldy crumbs. Consequently, when contaminated food goes in, contaminated feces come out. So, regarding cockroaches that have found their way indoors, some experts insist only an unsanitary kitchen produces unsanitary cockroaches. So, that’s the inside scoop on cockroach poop!

Clean or not, any home can suddenly become a playground for cockroaches. Sometimes they wander in through loose-fitting doors and windows during weather extremes. Often, they’ve just inadvertently hitched a ride in boxes, grocery bags, firewood or furniture. Once inside, they quickly find good reasons to stay: Furniture or appliances to hide under, or even sliver-sized spaces in baseboards, cabinets and floors are enough to provide safety. Humidity, which they like, is to be found in or under sinks. Food is readily available — the tiniest breadcrumb fallen to the floor can be a whole meal for a cockroach.

Cockroaches belong to the order Blattaria (blat-TARE-ee-uh) and superorder Dictyoptera (dick-tee-OP-terr-uh). Some experts believe cockroaches should be placed in their own order, Blattodea. “Cockroach” is from the Spanish word, Cucaracha (koo-kuh-RAH-chuh), meaning chafer beetle, while the Greek word for cockroach, blatta, gives rise to the name Blattaria.

Today, there are around 4,000 species of cockroaches in the world. Of all these species, only 10 make pests of themselves. About 57 species inhabit North America. Cockroaches are found everywhere in the world, except the Polar Regions, although they’re mainly tropical. 

Physical description
North American cockroach species range in size from 3/4-inch to 2 inches (2 – 5 cm) in length. Many are nocturnal and spend the daytime hiding in cracks and crevices or under yard debris. Most of us see them only briefly as they scurry away when we flip on an outdoor light. They’re speedy, but not so fast we can’t get a glimpse of the flattened, long-oval bodies and long legs. With some, the front part of their thorax (see insect anatomy here), called the pronotum (pro-NO-tum), may hide the head when viewed from above. Their body color ranges from yellowish-brown to reddish-brown to dark-brown.

Mitchell's Diurnal Cockroach, Polyzosteria mitchelli, held in the palm of someone's hand.

Some are pretty. This is Mitchell’s Diurnal Cockroach, Polyzosteria mitchelli, an Australian species. (Jean and Fred / Flickr; cc by 2.0)



The antennae (an-TEN-ee) are long and thin, often held sweptback. Antennae (sing: antenna) are used as feelers. A cockroach walking alongside a wall, for instance, will touch the wall with a feeler as it moves. One researcher nipped off small portions of the antennae of a hapless captive, little by little, and confirmed that the cockroach moved its body ever closer to objects to maintain antennae contact with them.

Cockroach standing with wings extended outward.

Under the “hood.” (Kasya / Pixabay; CC0)



Regarding their wings, the females of some species have only little nubs, and with some species both males and females are flightless. Most, though, have two pairs of functional wings which, at rest, are held folded flat atop the abdomen. Many seldom fly, but among the ranks of cockroaches are some excellent fliers ready to take off in an instant. There are two conspicuous appendages, call cerci (SER-sigh), at the end of their abdomen which function as sensory organs that detect vibrations and wind movement behind them, alerting them to approaching danger.

Habitat
Cockroaches live in groups in dark places, such as under mulch, bark, rotting logs and stones, or in storm drains, basements and, of course, buildings. They like warmth and humidity. For this reason, the most abundant populations live in the South. 

Food sources
Cockroaches are scavengers. They’ll eat nearly anything, including all kinds of human food, pet food, garbage, grease, paper, wood, leather, and even wallpaper paste.

Life cycle
Cockroaches go through incomplete metamorphosis (technically called hemimetabolism) — their life cycle progresses from egg to nymph (developing young) to fully grown adult.

When a female is ready to mate, she emits pheromones, which are chemical odors that attract males. Females of most cockroach species lay hardened, purse-shaped egg cases, called oothecae (oo-THEE-see; sing.: ooth-EEK-uh), containing from 12 to 25 eggs, in dark, humid crevices. The oothecae are formed within their body. 

Brown cockroach egg sac, or ootheca, laying on sandy surface.

Cockroach egg sac. (ootheca). (Jean and Fred / Flickr; cc by 2.0)



Some species, like American Cockroach females, carry an ootheca around for some time on the end of their abdomen before depositing it somewhere, or even until the eggs hatch. Some females deposit their oothecae under debris, where they’ll be hidden. Some species are apparently parthenogenetic: The females give birth to females that give birth to females. No males exist.

Cockroach eggs hatch in six to eight weeks. The young, called nymphs, look like tiny, wingless versions of their parents. They’re lighter in color at first, but as they outgrow and shed their outer skin a time or two (a process called molting), they become darker. Their wings, if any, will become fully developed and functional following their final molt. The nymphs will go through two to 14 molts, depending on the species. It may take up to a year or more, depending on the species, to reach full adulthood. A full life span is up to three years.

*Top photo: American Cockroach, Periplaneta americana. (Lynette Schimming / BugGuide.net; cc by-nc 3.0)
**Source: http://www.bbc.co.uk/nature/17839642

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