Cockroaches 2, 1

The common cockroach, Blatta orientalis

cockroach male

The common cockroach (Blatta orientalis male above and female below), which was introduced to the UK in the 16th century, is also known as the blackbeetle. It is probably the 2nd most important pest cockroach. The adults are a shiny dark brown. The male has wings which reach about 2/3 of the way down his body (see above left) and can fly. The female (below) has tiny wing buds or lobes and is unable to fly. They are around 20-27 mm long, and as their common name suggests, are black or dark brown at all stages in their lives. They are found everywhere except Antarctica, but is most common in the temperate regions of the world. They are often found outdoors, in basements and in colder areas of buildings. Their lifecycle takes 1 - 2 years.

cockroach female carrying egg case

cockroach egg case

Above is a cockroach ootheca, or egg purse of Blatta orientalis showing how the eggs are arranged inside, and above that is a female carrying the egg case. There are usually around 16 eggs inside, and a female can lay up to 9 of these in her lifetime.

When the eggs hatch they look like little worms, but very soon they moult to resemble a smaller version of the adult. The Nymphs moult 6 - 10 times before reaching adulthood. The female, above right is carrying her egg case. As with the Mantids the eggs are contained in an egg case or purse (ootheca) see the drawing above, and are carried around by the female attached to the tip of her abdomen for a few days before she deposits them; usually near a source of food. The ootheca contains from 16 to 40 eggs depending on the species.

German cockroach, Blatella orientalis

The German cockroach is probably the most important pest cockroach, and it is found worldwide. Both sexes look alike, with the female being slightly larger. And both have wings reaching the end of the abdomen, also both sexes can fly. They have a dark brown body and are up to 16 mm long, and can eat almost anything. The eggs case holds 20 - 40 eggs, and a female can lay up to 7 cases in her lifetime, and need mate only once to do so. They are found world wide, but only indoors in the colder months in the UK.

Periplaneta americana, the American cockroach

American cockroach body, Periplaneta americana body

Above is a female Periplaneta americana, the American cockroach. The 7 th abdominal segment is shaped to allow the discharge of the large egg case (see above).

The American cockroach is the 3rd most important pest species. It measures 35 - 40 mm long, and is chocolate brown in colour. Both sexes have wings, and both can fly, but their flight is weak. They are found world wide. Their lifecycle take 6 - 9 months to complete. Despite its name it is believed to have originated in Africa.

It is found in sewage and kitchens worldwide. It can cause allergies and asthma in some people.

Below are the mouthparts of the American cockroach, Periplaneta americana.

Cockroach mouthparts

Blaberus discoidalis, the Discoid cockroach

Blaberus discoidalis

Above is Blaberus discoidalis, commonly known as the Discoid cockroach, the Tropical cockroach, West Indian cockroach, Leaf cockroach, False death's head cockroach, Haitian cockroach, and the Drummer! It is native to central America. Adults reach 35 - 45 mm in length. Although the adults have wings and can fly, they rarely do. They cannot climb smooth vertical surfaces, and compared to other cockroaches they are relatively slow moving. Also they are less smelly than other cockroaches. Because of all the rather un-cockroach like behaviour, and because they are easy to rear in captivity, they have become popular as live food for insectivorous pets.