The German cockroach is the cockroach of concern, the species that gives all other cockroaches a bad name. It occurs in structures throughout Spain, and is the species that typically plagues multifamily dwellings.The German cockroach may be confused with the Asian cockroach, While these cockroaches are very similar, there are some differences that a practiced eye can discern.
Figure 1. Adult female German cockroach
Distribution
The German cockroach is found throughout the world in association
with humans. They are unable to survive in locations away from humans
or human activity. The major factor limiting German cockroach survival
appears to be cold temperatures. Studies have shown that German
cockroaches were unable to colonize inactive ships during cool
temperatures and could not survive in homes without central heating in
northern climates. The availability of water, food, and harborage also
govern the ability of German cockroaches to establish populations, and
limit growth.
Description
Egg. Eggs are carried in an egg case, or ootheca, by the
female until just before hatch occurs. The ootheca can be seen
protruding from the posterior end (genital chamber) of the female.
Nymphs will often hatch from the ootheca while the female is still
carrying it. A typical egg case contains 30 to 40 eggs. The egg case
is a tiny, brown, purse-shaped capsule. It is about 8 mm long, 3 mm
high, and 2 mm wide.
Larva or Nymph. The nymphal stage begins with egg hatch and ends with the emergence of the adult. Nymphs are dark brown to black in color, with distinct dark parallel bands running the length of the pronotum. Nymphs do not possess wings. The number of molts required to reach the adult stage varies, but the most frequently reported number of molts is six. The stage between molts is called an instar. At room temperature nymphs complete development in about 60 days. All developmental stages actively forage for food and water.
Figure 2. Oothecae (egg cases) of the German cockroach
Figure 3. First instar nymphs emerging from the oothecae (egg case) of a German cockroach
Adult. The adult is 10 to 15 mm long, brown to dark brown in color with two distinct parallel bands running the length of the pronotum. The sexes can be distinguished by the following characteristics: male - body thin and slender, posterior abdomen is tapered, terminal segments of abdomen visible, not covered by tegmina (leathery outer wings); female - body stout, posterior abdomen is rounded, entire abdomen just covered by tegmina.
Figure 4. Third instar nymph of German cockroach.
Figure 5. Newly molted adult German cockroach, Within a few hours the cuticle will harden and darken.
Figure 6. Adult male German cockroach.
Figure 7. Adult female German cockroach.
Life Cycle
The German cockroach has three life stages typical of insects with
incomplete metamorphosis: the egg, nymph, and adult. The entire life
cycle is completed in about 100 days. However, factors such as
temperature, nutritional status, and strain differences may influence
the time required to complete a life cycle. German cockroaches breed
continuously with many overlapping generations present at any one time.
Under ideal conditions, population growth has been shown to be
exponential. Actively growing field populations are comprised of 80
percent nymphs and 20 percent adults. The German cockroach is
omnivorous, eating table scraps, pet food, and even book bindings.
Medical and Economic Significance
German cockroaches adulterate food or food products with their
feces and defensive secretions, physically transport and often harbor
pathogenic organisms, may cause severe allergic responses, and in
extremely heavy infestations have been reported to bite humans and feed
on food residues on the faces of sleeping humans. In addition, some
scientists suggest that German cockroach infestations may cause human
psychological stress and that the stigma associated with infestations
alters human behavior. For example, people with infested houses do less
entertaining, and avoid the kitchen at night for fear of encountering a
cockroach.
Action Threshold
Since the German cockroach is considered an aesthetic pest, the
action threshold for this insect depends upon the tolerance of the
people living in the infested dwelling. However, most people associate
cockroach infestations with poor sanitary conditions and typically go to
excessive lengths to eradicate them from their houses.
Management
Insecticides Non toxic and low toxic alternatives for German cockroach control are available. Sticky traps can be used to monitor or reduce population size. Improving sanitation by eliminating food and water sources and clutter can have a significant impact on reducing the chances of infestation population size. Finally, exclusion practices such as sealing cracks and crevices will reduce harborage space and also negatively impact population size.
To arrange a survey or pest control treatment call Gray at Local Pest Spain
on 0034 952449591 or visit the website www.localpest.es
