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Few insects are as unwelcome in homes as cockroaches. If they get into food, they contaminate it with their feces and the disease-causing bacteria they carry on their bodies. But once they find a home they like, they settle in and reproduce so quickly that getting rid of them can be very difficult. Entomologists -- scientists who study bugs -- have classified more than 4,000 species of cockroaches. In the US, the four species most often found indoors are the German, American, Oriental and brown-banded cockroaches.
Cockroach Breeding Habits
After mating, female cockroaches deposit their eggs in a hardened oval capsule called an ootheca. When the eggs are almost ready to hatch, the mothers of most species either drop the egg case close to a food source, or use secretions from their mouths to glue it to a suitable surface. The eggs contain enough water to sustain the baby roaches until they hatch and are able to start foraging for food and water themselves.
German cockroaches die younger than any other North American roach species but in only 20 weeks of life, have huge families. They're about 1/2 inch long, light brown in color, with two lengthwise black stripes behind their heads. German cockroaches mature so fast that only a few weeks after hatching, they're ready to make babies of their own. When you take all the different generations into consideration, one female can be the matriarch of up to 35,000 roaches. This means that if one apartment gets them, they can rapidly spread through an entire building. Females can produce seven egg capsules in a lifetime, each holding as many as 48 eggs. The capsules stay attached to the mother until the eggs start to hatch.
The chestnut-colored American cockroach is the largest of the four species, measuring up to 2 inches in length, with a light yellow band around the edge of its head. Also called a "palmetto bug," these roaches like to breed in sewers, so you have to be especially careful to keep them from contaminating food with the germs they carry. American roaches live for about 30 months; halfway through that time, the females are mature enough to start breeding. At their peak, females can produce two egg cases a week, each containing up to 16 eggs, but after that, their reproductive capacity declines to about one case a month. The eggs incubate for six to eight weeks. In her lifetime, one female produces an average of 150 young.
Some parts of the Northwest, Midwest and Southern US have a particular problem with Oriental cockroach infestations. These roaches, sometimes referred to as "black beetles" or "water bugs," grow to about an inch in length and are dark brown to black in color. Their life span is highly variable -- from 34 to 189 days -- and during that time, females produce an average of eight egg capsules, each containing about 16 eggs. After carrying the capsules between 12 hours and five days, females deposit them in a warm, sheltered place where the babies, called nymphs, can find nourishment when they hatch.
Brown-banded roaches, identifiable by the two brownish bands extending laterally across the body, don't grow more than about 1/2 inch long. The other three common roaches have wings but almost never fly, but these ones, who like warm and dry habitats, do. Females, who live from 13 to 45 weeks, carry egg capsules for about 30 hours before sticking them in well-concealed spots, such as behind pictures or under furniture. Each capsule encloses about 13 eggs and, throughout her life, a female produces about 14 of them. Depending upon the temperature, the eggs can incubate from 37 to 103 days.
- University of Maine Extension: Insect Pests and Plant Diseases: Fact Sheets - Cockroaches
- University of Florida: Featured Creatures: American Cockroach
- Ohio State University Extension: Fact Sheet: American Cockroach
- North Carolina State University: Know Your Enemy: Cockroaches
- Pestworld for Kids: Cockroaches
- University of Florida: Featured Creatures: Oriental Cockraoch
- Penn State University Entomology: Brown-banded Cockroaches
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