- The cockroach we know today first came about 200 million years ago, while primitive roaches were first spotted about 350 million years ago.
- There are over 4,500 species of cockroaches in the world, but only 30 are considered pests.
- Thanks to their open circulatory system that allows them to breathe through their entire body, German cockroaches can live for nearly a week after having their heads severed.
- Cockroaches are very fast: they can cover up to 80cm/second and up to three miles in an hour; even one-day-old roaches can run nearly as fast as their parents.
- They can live without breathing for half an hour and last one month without food, but they only survive for a week without water.
- Cockroaches like to feel something solid touching their bodies, which is why they often squeeze into places that keep their bodies tight.
The adult measures 12 to 15 mm and weighs on average 0.100 g. In general, German cockroaches have a flattened, oval-shaped body, tan to dark brown in color, with spiny legs and long antennae. The male's body is slender and thin, and its abdomen is not covered by tegmina (outer wings), while females have larger bodies, rounded posteriors, and tegmina covering their entire abdomen. Nymphs are very similar to adults in appearance, but they are generally smaller, almost black in color, and exhibit a single stripe down their back (as opposed to two broad, parallel stripes displayed by adults). The eggs are tiny, brown capsules, measuring about 8 mm, and are carried in an ootheca (an egg case containing 30-40 eggs) by the female until they hatch.
Diet, Behavior, and Habits
German cockroaches choose as dwelling sites human residences where large quantities of garbage and detritus are available, from where they obtain the largest part of their diet. They eat a variety of foods (basically the same as those preferred by humans), including sweets, carbs, seeds, grains, meat, and grease, but also soap and toothpaste. They also feed on dead organisms.
German cockroaches prefer moist and warm environments such as bathrooms or kitchens, where they live in large groups and reproduce continuously. During the day, they hide in narrow cracks and holes around the house, while at night they go out foraging. Often, they may be spotted out of their hiding places during the day if they lack food, water, or if pesticides are being applied to their dwelling sites. Their head ganglia (nerve cell clusters located in their peripheral nervous system) allow them to visually perceive their environment, while subesophageal ganglia allows them to produce certain sounds to alert others of potential danger. They also use pheromones to signal mating, feeding, or the presence of predators in the area.
Sexually, German cockroaches are highly active and, given the necessary conditions, they can reproduce continuously (low temperatures usually slows down the breeding rate). Females produce 4-6 oothecae in their lifetime, giving birth to 3 to 4 generations. The eggs are carried by the female cockroach for 6 weeks before they are laid, after which they are stored in dark, safe places. Nymphs take about a month to hatch and reach independence in 65 days (on average).
Signs of Infestation
The most conclusive sign of a German cockroach infestation is seeing them around the house. However, they are nocturnal creatures and, unless the infestation is severe, you will not be able to spot them during daytime. The following may indicate a cockroach problem:
- shell casings (small, dark brown, oval-shaped)
- a strong, oily smell that can permeate exposed food and render it unpalatable
- dark-colored specks (basically fecal pellets and regurgitated food)
Common hiding places include:
- Around the kitchen sink
- Above ceiling panels
- Inside furniture
- Inside stalks of cardboard
- Inside stoves and refrigerators
- On damp floors
- In cupboards and cabinets
- Behind paneling
- In book cases
- In garbage containers and trash cans
- Basement rafters
- Inside microwave ovens
- Inside table legs
- In light switches
Management and Control
It may take a great deal of effort and persistence on your part, but it is possible to eradicate cockroach infestations. To obtain optimal results, a multi-tactic approach combining sanitation, mechanical control, and chemical control is needed – preferably carried out by a pest control professional who knows how to correctly diagnose and treat an infestation.
In large numbers, German cockroaches can cause a great deal of damage to people and properties, including:
- They alter food and make it unpalatable, which can result in large economic losses in regions where food is scarce
- They carry several bacteria and viruses on their bodies that are deposited on food and utensils during foraging; when contacted by humans, these organisms may cause gastroenteritis, diarrhea, dysentery, and several other diseases (including hospital-acquired illnesses)
- They act as allergens to people: their bodies, fragments, and waste can trigger asthma symptoms in sufferers
- While feeding, they can destroy books, paper products, and other items they come in contact with
Before initiating any treatment, it is imperative to conduct a thorough inspection to identify the amplitude of the infestation and reveal all harborage sites. This process is best conducted by a pest control professional, who will place sticky traps in certain strategic locations inside the residence in order to obtain the needed information for effective management and control.
As in the case of any other pest invasion, eliminating food, water, and harborage is the first step in eliminating the necessary conditions for their survival. Garbage and clutter are the main sources of food, so eliminating piles of debris, cardboard boxes, and other things lying around and collecting dust is extremely important. Clean cupboards, cabinets, and the areas behind appliances. Although sanitation alone is never sufficient to eliminate the entire cockroach population and prevent future problems, it may go a long way in reducing the existing population and increasing the efficiency of other treatments.
Baiting using hydramethylnon, sulfuramid, boric acid, or fipronil is an effective method of controlling German cockroach populations, especially when used in conjunction with insecticidal dusts such as silica aerogel, diatomaceous earth, and boric acid. The latter work best when applied to cracks and holes inside desks, inside ceiling light fixtures, in hollow legs of chairs, and in wall and floor crevices. Sprays and foggers found in supermarkets may actually do more harm than good in case of severe infestations, since they cannot effectively control large populations, and they only work to disperse them, making control more difficult.
Contrary to common belief, cockroaches are not an indication of a dirty house - the infestation usually starts with the introduction of infested materials – but an unclean house will certainly contribute to the spreading of the infestation. To make sure you are not bringing – or keeping - them inside your house, do the following:
- Thoroughly clean areas beneath sinks, stoves, refrigerators, cupboards, and cabinets
- Do not bring any used appliances or furniture inside the house without first inspecting them carefully (look for live cockroaches, but also egg cases)
- Immediately clean spilled drinks and scraps of food; also, don't leave dishes in the sink overnight
- Store food in tightly-sealed containers and keep garbage in cockroach-proof receptacles stored away from the house
- Don't leave pet food in the dish overnight
- Repair leaking pipes, insulate and tape off gaps between pipes and walls, and seal cracks and crevices with caulking materials