© Stuart M Bennett 2003
Blatta orientalis
(The Common or Oriental Cockroach)


As the name says, this is said to be the most common cockroach in the U.K. but there are differences of opinion about this, suffice to say there are plenty of these about and as I said earlier, they are found in areas of high temperature such as kitchens, laundry's and hospitals etc.  As you can see from the picture below the male has wings, though he can't fly, and the female has only vestigial wings stubs, the picture above is a female.  These are wings which have devolved over the millennia as the female never flies, so identification of the sexes in this species is quite easy, if you're into that sort of thing. A few facts below will bring home the need for control of this species of insect:-

This species is dark brown to black in color. Females are 1 to 1-1/2 inches long and have only rudimentary wings reduced to small lobes. Males are a little shorter than females and have fully developed wings which don't extend to the end of the abdomen. A female will carry her ootheca for about 30 hours before she drops or attaches it to a protective surface near a food supply. The average female will produce 8 capsules, each having 16 eggs which hatch in about 44 days.

This species is less wary and more sluggish than other common cockroaches. It may enter the home in food packages and laundry, or merely come in under the door or through air ducts or ventilators. It's common in sewers, utility chases, in dark, damp basements, and is known to climb water pipes to upper floors in blocks of flats. This is a notably gregarious species, commonly being found in large colonies.

 A few facts :-

  • They are 25-30mm long.
  • They are dark brown to black.
  • Wings are undeveloped in the female, and only cover 3/4 of the length of the abdomen in the male, this can be seen in the picture below.
  • The female will produce 5-10 oothecae (egg cases) in her life time.
  • There are 16 eggs inside the egg case (Oothecae). Phew.! imagine if all that lot survived.
  • The hatching time of the eggs is about 2 months.
  • The nymph, when it hatches, will moult up to 10 times before it reaches adulthood.
  • The development of the nymph can take up to 9 months, but can be as little as 5 months, then they too are off laying.

Why do we worry about cockroaches? because there is no clear cut evidence to link them to disease outbreaks.

Well, they have been found to be carrying a number of diseases, mainly because of the areas that they frequent such as sewers, heating ducts, waste disposals etc. A few are listed below:-

  • Salmonella                                      Food poisoning
  • Mycobacterium tuberculosis            Tuberculosis
  • Entamoeba histolytica                     Amoebic dysentry
  • Escherichia coli                              Gastro-enteritis
  • Ancylostoma spp.                            Human and Dog Hookworms
  • Taenia sp.                                       Tapeworm
How do I know that I have cockroaches?

Well you know when you come in from the pub half drunk and you go into the kitchen about two in the morning and the floor moves underfoot and tends to make a crunching sound.....?  Well then you've probably got them.

Seriously, cockroach infestation in the home is quite rare these days unless you have been unlucky bringing one in on say a box of produce.  In the old days, not so long ago, a lot of people used to burn coke on their fires.  Coke is made in a coking plant where coal is heated, in the absence of air, and degassed.  At the end of the process, the resulting product (Coke) is drenched with water to cool it down hence we get very hot and steamy conditions which are ideal for cockroaches.  Cockroaches lay egg cases (Oothecae) and when the coke was bagged so were the Oothecae.  Consequently when the coke was delivered, so were the Oothecae.  Infestations used to live behind the old ranges that people used to have in their back parlours or kitchens which these days a lot of people have removed and in any case coke isn't a common fuel now.

Indicators are:-

Cockroach marks - This is liquid excreta produced by cockroaches when there is plenty of water about they are usually brown and much bigger than the marks left by a fly and are numerous near the habourages. Below is an old black and white picture of German cockroaches and the faecal marks.

  • Faecal pellets - These tend to be found when there isn't much water about and look a bit like mouse droppings, but they are only 2 mm long and brown to black in colour.
  • Egg Cases (Oothecae) - These can some times be seen if the main breeding area is found.  Some examples of Oothecae can be seen below:-
  • Obviously, if you come downstairs in the middle of the night and the floor crunches then you have live insects this being another indicator.
  • You may, if you're good, find cast nymphal skins.  You need eyes like a hawk unless there are loads about.
  • Sometimes there is a smell, don't ask me to describe it other than it is a roachy smell.  You need to smell it to know it.

OK! so what can I do.....in a nutshell, you can't do nowt (that's nothing in southern terms).  The only way to possibly cure cockroaches is to call in a pest control company, who knows what they are doing.  Curing the problem means finding the breeding areas, if they are accessible, and also treatment with insecticides. Making sure that a residual insecticide is kept active so that any nymphs hatching out do so straight onto an insecticidal surface.  In short Guys and Gals, it is going to cost you a bit of cash, so just hope and pray that you don't get them......!

For Pest control chaps there is a detailed explanation of cockroach control HERE...!

Oriental ootheca holding 16 eggs/nymphs

Back to main Cockroach page