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German Cockroaches


Blattella germanica


colour: Light brown to tan with two almost parallel, dark longitudinal stripes, bars, or streaks on shield; female darker than male.
Legs: Six
Shape: Larger, Oval
Size: German cockroach adults are about 1/2-5/8 in (13-16 mm) long.
Antennae: Yes
Flight: No


German cockroaches may live throughout a building, but especially in warm and humid places, such as kitchens, bathrooms, and bedrooms and dens where people eat casually. They spend about 75% of their time hidden away in cracks and crevices. Smallest nymphs only need about a millimetre of space, while adults need about 5 mm. Roaches eat all types of food, as well as things like soap, glue and toothpaste.


German cockroaches can come inside a structure with paper products and packaging, and used appliances. In summer they may move from one building to another. They can survive outdoors if it is warm, although this is uncommon. German cockroaches are the most common, and have the most impact as a nuisance. They are known to transmit disease organisms, and cause allergic reactions in some people.


Because German cockroaches rapidly reproduce, a highly-skilled pest management professional is best suited to eliminate an infestation. Usually and initial “clean-out” service is needed consisting of an extensive, detailed treatment to all cracks and crevices, areas, etc, followed by a regular preventive maintenance program. Harbourage and food source removal enhances the effectiveness of control through proactive IPM processes and communication.


“Biological Potential” of Cockroaches. *
Biological potential means: “How long does it take for a population to get very large? and “How large can it get?”


The answer to biological potential depends upon several factors: (1) How many egg s are in an average capsule? (2) How many egg capsules will a female produce on the average capsule? (3) How long does it take for the first instar nymph to become an adult cockroach capable of mating and producing another generation?


A LITTLE MATH: The real key to “biological potential” rests upon the length of time from egg to mature adult. Let’s do a little math to see why we can make such a statement. Basic formula for biological potential: Number of embryos per oothecae produced per year = Number of mature adults per year.


If we start with one pregnant German cockroach that has 30 embryos in her egg capsule and she lays 5 egg capsules, we will have 30 x 5 = 150 mature adults in three months. If half of these are females and they all mate, we will have 5,625 pregnant females at the six month time frame If each of these females lays 5 capsules, each containing 30 embryos, we will have 75 x 5 x 30 = 11,250 mature adults by the time six months has elapsed. If half of these females lays 5 egg capsules, each containing 30 embryos, we will have 5,625 x 5 x 30 = 843,750 mature adults at the nine-month period. If half of these adults are females, and they all mate, we will have 412,875, pregnant females at the nine-month time frame. If each of these females lays 5 egg capsules, containing 30 embryos, we will have 421,875 x 5 x 30 = 63,281,250 mature adults by the end of the year. That’s more than 63 million, that started with one single pregnant cockroach at the beginning of the year.


*Ehmann, Norm. “German Cockroaches: The Industry’s Bread and Butter.” Pest Control Technology July 2008. P72