endorsed by 350 million
years of life on earth. They are real "living fossils", as an enormous
species have existed since the Carboniferous period with a persistence
successful and adaptable structure.
diversity and extent to which they are represented in that geological
clearly indicates that there was a long previous evolution of roaches
left no vestiges. There are now more or less 3500 living wild species.
here we are interested mostly in those few species that have adapted to
of the civilized man and to the human environment, becoming a plague
by all housewives and owners of bars, restaurants, supermarkets and
depositories of all types; thanks
fertility, adaptability to all kind of foods, and especially to their
behavior that assures them of relatively few encounters with man.
picture clearly show why the cockroaches are capable of colonizing very
cracks in floors, walls and furniture.
to most of the chemical pesticides that where intended to control them,
they end up developing resistance to them. So the modern way for the
of cockroaches is turning out to be the old methods of physical control
papers covered with sticky substances.
the Appendix for some old but
the world the species of cockroaches that have been successful in man's
are Periplaneta americana, Blatta orientalis, Blatella germanica,
Blaptica dubia, Suppella supellectillium, Suppella longipalpa, etc.
Except for Blaptica
dubia, from South
America, the other four
genera are perfectly adapted to Europe.
In Durango (Dgo.) Periplaneta
americana is common in the city,
living mainly in the culverts. We suffered in Hermosillo (Sonora) the invasion of the house by Blatella
germanica, and in Cancún (Quintana Roo) we have found up
now P. americana and Blatta orientalis.
have to be deceived by the name of Periplaneta
americana. According to one author writing on the
internet, the origin and dispersion center of this highly invasive
species is Africa from where it arrived at the United States in 1625. Linnaeus, created in 1758
the genus Blatta in which he included
the species americana (surely because the available specimens were from America), and Burmesteir in 1838 created
the genus Periplaneta to hold americana.
to see images of the different species, can make use of their favorite
including in the search the complete species name, written between
of the web literature is related to the “pest” control, and companies
ventral view, approx. 3x natural size.
ventral view, approx. 3x natural size.
of this season (June-July) force the roaches to leave their hiding
the daylight, terrifying the housewives that take care of their house
collaborates in the control of the plague by fumigating with
little adoption of ecological criteria and techniques. This provided me
to illustrate this article. If I wanted I could have had dozens at my
head, frontal view
head, ventral view
Whoever wants a more thorough in depth view on the world
of cockroaches, including those species that
some use as pets, like the sizzling cockroach of Madagascar, and other
species that herpetologists raise as food for their other pets
snakes), can visit these Internet addresses:
of a cockroach is a magnificent example of the structure of an insect.
explains why several educational pages on the internet describe it in
best one by its didactic quality and beautiful macro and
images, is this site of the University of Alberta:
complete and descriptive site, but illustrated only with drawings, is
the one of
Prof. Fox, at the Lander
The notes that
follow will serve as a guide for those who wish to try the
investigation of a cockroach.
|The cockroach leg is not
totally typical. Normally the coxa is a small segment and the
trochanter an important one; a design that is inversed in this case.
to dissection and justification of its use
has ethical doubts on this type of operation he can find an important
of this subject at:
religious people and strict vegetarians by, for example imitating San Benito, walk with care to ensure they don't squash
even an ant. But most of the non-religious or ideological objections
in the avoidance of dissections in schools and colleges as they are
considered cruel and in bad taste, (which according to my own
school when 13 years old, is really sound). To avoid where
possible the extent of animal suffering under experimentation, when
that is inevitable
research, suitable methods of anesthesia and euthanasia are used.
|From upper left going clockwise: claw
of the pretarsus in lateral view; pretarsus in dorsal
view; a ventral view of the pretarsus. The three pictures show clearly
an adhesive cup that allows cockroaches to climb vertical walls, even
polished ones. The fourth picture shows through the translucent
skeleton the dense net of tracheae that oxygenates the
powerful leg muscles.
desired to learn the principles of parasitological investigation,
branch of general biology, agriculture, veterinary medicine and
human medicine, dissection is an essential practice. But you must
In schools the use of real dissections (the specimens usually adopted are frogs,
and cockroaches) can perhaps be
replaced with great
disadvantage of course by the use of virtual reality software or more
three dimensional images of some good dissections, or
with drawings, based on the same source. This could probably save
thousands of specimens used annually in schools.
cannot be forgotten that the anatomy of the animals thus represented,
must necessarily be taught to the students, was discovered by
made the necessary dissections and published the corresponding
da Vinci and Vesalio had not dissected human beings, we would
perhaps still believe that the veins and arteries (like the tracheas of
empty tubes that transported air from the lungs to body tissues. And
learnt to dissect, no surgeon could save lives via a surgical
hope that some of the images presented here can be used with that aim.
the images of the University of Alberta's website, the only dissection
English) extensively mentioned on the internet is a promotion of a
video tape, and is illustrated online only with
images, several of which are semi-concealed by a band of lines.
abdomen: note the acute end, the two sensitive cerci, and the short
male: note the rounded end, the two anal stylets and the long wings.
Now we have the information
need to proceed with our cockroach dissection.
complete, detailed and magnificently informed dissection, see the
referred to previously.
will not lose the opportunity to study the pretarsus of the legs that
the secret of why cockroaches climb vertical walls, the structure of
trachea with its characteristic chitinous spiral support, the abundant
in the abdomen, the structure of the compound eye of an insect with top
lighting, the wings and antennae, etc.
if a microscopist
has hypochlorite, or even better sodium or potassium hydroxide, they
may want to
the mouthparts of the insect.
will only give the directions to separate the alimentary canal, from
will extract the parasites.
to the interests of the
dissection can be made dorsally or ventrally. The ventral way is the
you want to study the intestinal fauna, so it is the one to be used
if a representative research is to be conducted, enough male and
cockroaches, as well as nymphs, must be dissected to give a
this article only a few adults of both sexes are used.
authors assign to the adults of P. americana a length of up to 44 mm. In Cancún and Durango I have only been able to measure
(on some tens of individuals collected) a maximum body length of 35 mm. Ten
significant when making such small insect dissections.
A list of
the parasites I have found is:
These species will be described in the
following parts of this series. I heartly acknowledge the help of
B. Camino, helminthologist at the University of La Plata, La Plata
Bs.As., República Argentina, for the confirmation of the
nematode genera to be described here.
If they are not a real nuisance, and if their
activities are limited to the garden or the wild, leave them alone. In
have an important role in the disposal of ecosystem detritus. Use all
efforts not to offer them a way into your house. A clean house,
without many crevices, and without poorly stored food, rarely
suffers from large cockroach invasions. Attempt to control them only if
their populations increase beyond that of some occasional visible
The oldest and most efficient method is
the use of boric acid crystal powder at sites near the
cockroach retire and procreate. They eat the sharp crystals which
cause bleeding of the gut.
breathe the powder, use rubber gloves to prepare the bait.
- One half cup
(350 grams) boric acid - looks like white powder and is
available in pharmacies
- one cup flour
- two heaped
spoonfuls of sugar
boric acid, flour and sugar.
Moisten with just enough water to make a paste that can be formed into
small cylinders or balls.
Make as many of them as you can. Distribute them in critical concealed
Nowadays, with exactly the same rationale is the use of
ground diatomaceous earth; not the powder for domestic
pool filters, but
the type sold by many garden centres to control insect pests.
have very sharp silica fragments.
If this seems cruel, think of the
insects (cockroaches and who knows what else) inmobilized by neurotoxic
chemicals, condemned to die of
and starvation. And of the collateral effects of this type of
the whole ecosystem. Such methods kill not only cockroaches, but
insect within its reach, and has accumulative and deleterious effects
birds and rodents that eat the carcasses.