Cockroaches

views updated May 18 2018

Cockroaches

KEY TERMS

Resources

Cockroaches are insects in the order Blattaria. They are somewhat flat, oval-shaped, leathery in texture, and are usually brown or black in color. Cockroaches range in body size from 0.12.3 inches (2.560 mm), and are rampant pest insects in human-inhabited areas, as well as common outdoor insects in most warm areas of the world.

These insects were formerly classified in the order Orthoptera, which consists of the grasshoppers and katydids. Now they are often classified along with the mantises in an order referred to as Dictyoptera. The separate order Blattaria, however, is the more common classification for them, and this order is placed in the phylogeny, or evolutionary history, of the class Insecta between the orders Mantodea, the mantids; and Isoptera, the termites.

The primitive wood-boring cockroaches in the family Cryptocercidae, a family in which there is only a single species in the United States, Cryptocercus punctulatus, are thought to have shared a common ancestor with termites. The evidence for this is a close phylogenetic relationship between the two groups obligate intestinal symbionts, single-celled organisms called protozoans, which break down the wood that the insects eat into a form that is useful to the insect, and in turn receive nutrition from matter that is not nutritive to the insect. There are also behavioral similarities between these wood-boring cockroaches and termites, including the fact that they both live gregariously in family groups, a characteristic not shared by any of the other types of cockroaches. Finally, the relationship between the two orders is evidenced by the resemblance between Cryptocercus nymphs and adult termites.

Interesting morphological characteristics of these insects are their chewing mouthparts and large compound eyes. The pronotum, or segment of the thorax closest to the head, conceals the head, and, in most species, both male and female are winged, although they rarely fly. They exhibit many fascinating behaviors, such as the ability to stridulate, that is, produce sound by rubbing a comb-like structure with a scraper. Other species, however, communicate by producing sound by drumming the tip of their abdomen on a substrate. An important developmental feature of these insects is their paurometabolous life-history. Paurometabolism is a type of simple metamorphosis in which there are definite egg, immature or nymph, and adult stages, but no larval or pupal stages and in which the nymphs resemble the adults except in size, development of wings, and body proportions. Habitat requirements of nymphs and adults do not vary in paurometabolous insects, a fact which helps cockroaches to thrive under a rather generalized set of environmental conditions at all stages of their lives.

Cockroaches are saprophagous insects, or scavengers, feeding on a great variety of dead and decaying plant and animal matter such as leaf litter, rotting wood, and carrion, as well as live material. They are, thus, very flexible in their diet, and this flexibility allows them to exist under a wide range of conditions. In fact, the habitat types of this order span such areas as wood rat nests, grain storage silos, forest leaf litter, and nests of leaf cutter ants. They thrive in areas with moisture and warmth.

KEY TERMS

Obligate intestinal symbiont An organism that lives in the intestinal tract of another organism, and whose presence is necessary for the survival of the host. Intestinal symbionts are usually bacteria or protozoans.

Oothecae Egg sacs produced by some insects including cockroaches.

Paurometabolism A type of simple metamorphosis in which the nymph, or immature, stage of the insect resembles the adult except in size, proportion, and wing length, and whose habitat requirements are the same as those of the adult.

Phylogeny A hypothesized shared evolutionary history between members of a group of organisms based on shared traits of the organisms; also known as evolutionary trees.

Saprophagous Refers to decomposer organisms that eat dead and decaying plant and animal matter.

Simple metamorphosis A developmental series in insects having three life-history stages: egg, nymph, and adult.

Cockroaches produce oothecae, sacs in which the eggs are held and protected by secretions produced by the female. These egg sacs may be carried by the female externally until the time of hatching, or internally until the female gives birth to live young, or they may simply be deposited on a suitable substrate and left to hatch without any care from the female.

Besides being rather fast runners, many cockroaches have other adaptations that allow them to escape from predation. One such defensive adaptation is the ability to produce an offensive odor, which they emit when disturbed. Other species, such as the Madagascaran cockroach, Gromphadorhina laevigata, force air out through their spiracles, thus producing an intimidating hissing sound.

Cockroaches are worldwide in distribution, although most of this orders approximately 4, 000 species occur in the tropics. In the United States and Canada, there are some 29 different genera, and about 50 species. Most of these species occur in the southern United States.

Due to their preference for moist, warm places, flexible diet, and nocturnal activity, cockroaches are very successful at living uncontrolled in human areas. Although annoying and often feared by people, they are not known to be significant disease carriers, crop pests, or agents of other large-scale damage to human areas. There are four species in North America which are common as household insects. They are the German cockroach (Blattella germanica ), American cockroach (Periplaneta americana ), brown-banded cockroach (Supella longipalpa ), and oriental cockroach (Blatta orientalis ). The oothecae of these indoor species are often deposited on common household items such as cardboard boxes, and in this way may be transported from place to place before they actually hatch, thereby spreading to new areas.

In contrast to its image as a fearsome but relatively harmless pest, the cockroach has for many years actually benefitted humans by contributing greatly to our general understanding of physiology due to its use as a model study organism in biological research investigating nutrition, neurophysiology, and endocrinology. Medical knowledge has expanded as a result of the data gained from such studies of the cockroach.

Resources

BOOKS

Arnett, Ross H. American Insects. New York: CRC Publishing, 2000.

Borror, D. J., C A. Triplehorn, and N. F. Johnson. An Introduction to the Study of Insects. 6th ed. Orlando, FL: Harcourt Brace College Publishers, 1989.

Carde, Ring, and Vincent H. Resh, eds. Encyclopedia of Insects. San Diego, CA: Academic Press, 2003.

Cornell, P.B. The Cockroach. London: Hutchinson, 1968.

Elzinga, R. J. Fundamentals of Entomology. 3rd ed. Englewood Cliffs, NJ: Prentice-Hall, 1987.

OTHER

Centers for Disease Control: National Agriculture Safety Database. Cockroaches <http://www.cdc.gov/nasd/docs/d001201-d001300/d001251/d001251.html> (accessed November 15, 2006).

University of Massachusetts, Amherst: Biology Department. The Cockroach FAQ <http://www.bio.umass.edu/biology/kunkel/cockroach_faq.html> (accessed November 15, 2006).

Puja Batra

Cockroaches

views updated May 29 2018

Cockroaches

Cockroaches are insects in the order Blattaria. They are somewhat flat, oval shaped, leathery in texture, and are usually brown or black in color . Cockroaches range in body size from 0.1 to 2.3 in (2.5 to 60 mm), and are rampant pest insects in human inhabited areas, as well as common outdoor insects in most warm areas of the world.

These insects were formerly classified in the order Orthoptera, which consists of the grasshoppers and katydids. Now they are often classified along with the mantises in an order referred to as Dictyoptera. The separate order Blattaria, however, is the more common classification for them, and this order is placed in the phylogeny , or evolutionary history, of the class Insecta between the orders Mantodea, the mantids, and Isoptera, the termites .

The primitive wood-boring cockroaches in the family Cryptocercidae, a family in which there is only a single species in the United States, Cryptocercus punctulatus, are thought to have shared a common ancestor with termites. The evidence for this is a close phylogenetic relationship between the two groups' obligate intestinal symbionts, single-celled organisms called protozoans which break down the wood that the insects eat into a form that is useful to the insect, and in turn receive nutrition from the matter which is not nutritive to the insect. There are also behavioral similarities between these wood-boring cockroaches and termites, including the fact that they both live gregariously in family groups, a characteristic not shared by any of the other types of cockroaches. Finally, the relationship between the two orders is evidenced by the resemblance between Cryptocercus nymphs, and adult termites.

Interesting morphological characteristics of these insects are their chewing mouthparts and large compound eye . The pronotum, or segment of the thorax that is closest to the head, conceals the head, and in most species, both male and female are winged, although they rarely fly. They exhibit many fascinating behaviors, such as the ability to stridulate, that is, produce sound by rubbing a comb-like structure with a scraper. Other species, however, communicate by producing sound by drumming the tip of their abdomen on a substrate. An important developmental feature of these insects is their paurometabolous life-history. Paurometabolism is a type of simple metamorphosis in which there are definite egg, immature or nymph, and adults stages, but no larval or pupal stages and in which the nymphs resemble the adults except in size, development of wings, and body proportions. Habitat requirements of nymphs and adults do not vary in paurometabolous insects, a fact which helps cockroaches to thrive under a rather generalized set of environmental conditions at all stages of their lives.

Cockroaches are saprophagous insects, or scavengers, feeding on a great variety of dead and decaying plant and animal matter such as leaf litter, rotting wood, and carrion, as well as live material. They are, thus, very flexible in their diet, and this flexibility allows them to exist under a wide range of conditions. In fact, the habitat types of this order span such areas as wood rat nests, grain storage silos, forest leaf litter, and nests of leaf cutter ants . They thrive in areas with moisture and warmth.

Cockroaches produce oothecae, sacs in which the eggs are held and protected by secretions produced by the female. These egg sacs may be carried by the female externally until the time of hatching, or internally until the female gives birth to live young, or they may simply be deposited on a suitable substrate and left to hatch without any care from the female.

Besides being rather fast runners, many cockroaches have other adaptations that allow them to escape from predation. One such defensive adaptation is the ability to produce an offensive odor which they emit when disturbed. Other species, such as the Madagascaran cockroach, Gromphadorhina laevigata, force air out through their spiracles, thus producing an intimidating hissing sound.

Cockroaches are worldwide in distribution, although most of this order's approximately 4,000 species occur in the tropics. In the United States and Canada, there are some 29 different genera, and about 50 species. Most of these species occur in the southern United States.

Due to their preference for moist, warm places, flexible diet, and nocturnal activity, cockroaches are very successful at living uncontrolled in human areas. Although annoying and often feared by people, they are not known to be significant disease carriers, crop pests , or agents of other large-scale damage to human areas. There are four species in North America which are common as household insects. They are the German cockroach (Blattella germanica), the American cockroach (Periplaneta americana), the brown-banded cockroach (Supella longipalpa), and the oriental cockroach (Blatta orientalis). The oothecae of these indoor species are often deposited on common household items such as cardboard boxes, and in this way may be transported from place to place before they actually hatch, thereby spreading to new areas.

In contrast to its image as a fearsome, although relatively harmless pest, the cockroach has for many years actually benefitted humans—a benefit that has resulted from its abundance and often large size. The cockroach has contributed greatly to our general understanding of physiology due to its use as a model study organism in biological research investigating nutrition, neurophysiology, and endocrinology. Medical knowledge has expanded as a result of the data gained from such studies of the cockroach.


Resources

books

Arnett, Ross H. American Insects. New York: CRC Publishing, 2000.

Borror, D. J., C A. Triplehorn, and N. F. Johnson. An Introduction to the Study of Insects. 6th ed. Orlando, FL: Harcourt Brace College Publishers, 1989.

Carde, Ring, and Vincent H. Resh, eds. Encyclopedia of Insects. San Diego, CA: Academic Press, 2003.

Cornell, P.B. The Cockroach. London: Hutchinson, 1968.

Elzinga, R. J. Fundamentals of Entomology. 3rd ed. Englewood Cliffs, NJ: Prentice-Hall, 1987.

periodicals

Roth, L. M. "Evolution and Taxonomic Significance of Reproduction in Blattaria." Annual Review of Entomology 15 (1970): 75-96.


Puja Batra

KEY TERMS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Obligate intestinal symbiont

—An organism that lives in the intestinal tract of another organism, and whose presence is necessary for the survival of the host. Intestinal symbionts are usually bacteria or protozoans.

Oothecae

—Egg sacs produced by some insects including cockroaches.

Paurometabolism

—A type of simple metamorphosis in which the nymph, or immature, stage of the insect resembles the adult except in size, proportion, and wing length, and whose habitat requirements are the same as those of the adult.

Phylogeny

—A hypothesized shared evolutionary history between members of a group of organisms based on shared traits of the organisms; also known as "evolutionary trees."

Saprophagous

—Refers to decomposer organisms that eat dead and decaying plant and animal matter.

Simple metamorphosis

—A developmental series in insects having three life-history stages: egg, nymph, and adult.

Cockroaches

views updated May 23 2018

Cockroaches

Cockroaches are winged insects found in nearly every part of the world. Although they are one of the most primitive living insects, they are very adaptable and highly successful. Some of the species have invaded human habitats and are considered pests since they can spread disease.

"Crazy bug"

Cockroaches or roaches belong to the order Blattaria, which means "to shun the light." They were given this scientific name because they sleep and rest during daylight hours and come out mainly at night. Their common name, however, is a version of the Spanish word cucaracha, which means "crazy bug." If you have ever seen one running away from you in a typical wild and zigzagging way, you know how they got their name. There are some 4,000 species or kinds of cockroaches living in nearly every habitat except Antarctica. All of them prefer to live where it is warm and moist, or where they can at least get water, so it is not surprising that they will move into people's homes if given the chance. Actually, only about 35 of these species are ever associated with people, and the other nearly 4,000 species live throughout the world, although the largest numbers are found in the tropics.

Cockroaches can be interesting, and some would even say fascinating. They can range in length from only 0.1 to 3.2 inches (2.5 to 8.1 centimeters). They seldom use their wings to fly, although some can fly around. Their bodies have a waxy covering that keeps them from drowning. They also can swim and stay underwater for as long as ten minutes. They will rest in one spot without moving for eighteen hours a day, and can go a long time without food. They eat only at night. As for what they eat, they are omnivorous (pronounced om-NIH-vaw-rus), meaning that they can and will eat anything, plant or animal. The more we learn about their diet, the more disgusting they seem, since they eat everything, including animal feces. Although they will eat wood, which is made up of cellulose, they are unable to digest it on their own and, thus, depend on certain protozoa (pronounced pro-toe-ZO-uh) or single-celled organisms that live in their digestive tracts or gut, to break the cellulose down. They make sure they always have these protozoa in their systems by eating the feces of other cockroaches.

Words to Know

Exoskeleton: An external skeleton.

Omnivorous: Plant- and meat-eating.

Oviparous: Producing eggs that hatch outside the body.

A versatile insect

Cockroaches are escape artists whose zigzag darting is done at what seems lightning speed. They can climb easily up vertical surfaces and have such flat bodies that they can hide in the tiniest of cracks and crevices. They have compound eyes (honeycomb-like light sensors) and antennae that are longer than their bodies, which they use to taste, smell, and feel. They even have a special organ in their mouths that allows them to taste something without actually eating it. Each of their six strong legs has three sets of "knees," all of which can sense vibrations and therefore serve as an early warning system. They also have little motion detectors on their rear end, which explains why they are so hard to catch and stomp. Although females mate only once in their lifetimes, they will stay fertilized all their lives and keep producing eggs without the help of a male cockroach.

Habits and anatomy

Like most other insects, cockroaches have an exoskeleton, meaning their skeleton is located on the outside of their bodies. They have three simple body parts: the head, thorax, and abdomen. Their head is dominated by their long antennae that are constantly moving and sensing the environment. These long, whiplike feelers are used to taste, smell, and feel things, as well as to locate water. To a cockroach, its antennae are more important than its compound eyes on top of its head. Their mouths have jaws that move from side to side instead of up and down, and their versatile mouths allow them to bite, chew, lick, or even lap up their food. They also have unique parts in their mouth called "palpi" that come in handy when humans try to poison them since it allows them to taste something without having actually to eat it.

Its thorax is the middle section of the body; the insect's six legs and two wings are attached to it. Two claws on each foot, plus hairs on their legs, enable them to hold on tightly or climb a wall easily. Their legs are strong and can propel them up to 3 miles (4.8 kilometers) per hour. The abdomen is the largest part of their body, and has several overlapping sections or plates that look like body armor. Their brain is not a single organ in their head, but is rather more like a single nerve that runs the length of their bodies. Their heart is simple, too, looking more like a tube with valves, and their blood is clear. They do not have lungs, but instead breathe through ten pair of holes located on top of the thorax.

Although females mate only once with a male, they stay fertilized and will keep making baby roaches until they die. Most species are oviparous (pronounced o-VIH-puh-rus), meaning the fertilized eggs are laid and hatch outside of

the mother's body. She can produce up to fifty babies at once, sometimes within only three weeks. The hatched eggs produce nymphs (pronounced NIMFS), which look like miniature adults. As the new roach grows, it sheds or cracks its outer skin and drops it or molts, growing a new, larger covering. Its does this as much as twelve times before it reaches adulthood. Cockroaches can live anywhere from two to four years.

Aside from most people's natural dislike of any sort of "bug" crawling around where they live, the fact that cockroaches can carry diseasecausing microorganisms gives us a very good reason not to want to have them in our homes. Outside or in their natural habitat, they have many natural enemies, including birds, reptiles, mammals, and even other insects. But in our homes none of these usually exist, so cockroaches can reproduce continuously unless removed. Poisons must be used carefully in the home, and it is important first to deny cockroaches access to the indoors by filling cracks to the outdoors. Their food supply can be restricted if we do not leave out any food overnight and keep the kitchen counters and floors swept of crumbs. Leaky faucets and half-full glasses will also provide them with the water they need, so it is important to deny this.

There are four common types of cockroaches that many of us know, sometimes too well. The dark American cockroach is large and is sometimes called a "water bug" or "palmetto bug." The German cockroach is the smallest and has two black streaks down its back. The Australian cockroach is a smaller version of its American cousin, and the Oriental cockroach is reddish-brown or black and is often called a "black beetle." Despite most people's natural dislike of cockroaches, some keep them as pets in an escape-proof terrarium. This recalls an old Italian expression that is translated as "Every cockroach mother thinks her baby is beautiful."

[See also Insects; Invertebrates ]

cockroaches

views updated May 21 2018

cockroach

views updated May 21 2018

cock·roach / ˈkäkˌrōch/ • n. a beetlelike insect (order Dictyoptera) that feeds by scavenging. Among the several species that have become established worldwide as pests in homes and food service establishments is the American cockroach (Periplaneta americana).

cockroach

views updated May 21 2018

cockroach (roach) Member of a group of insects with long antennae and a flat, soft body found worldwide, but mostly in the tropics. Its head is hidden under a shield (pronotum) and it may be winged or wingless. Eggs are laid in considerable numbers in special egg cases. Some species are serious household pests. Length: 13–50mm (0.5–2in). Family Blattidae.

cockroaches

views updated May 21 2018

cockroaches See Dictyoptera.

cockroach

views updated May 23 2018

cockroach XVII (cacarootch, cockroche). — Sp. cucaracha; unaccountably assim. to cock and roach.