Hated by many but liked by some

Finding a cockroach in an unopened bottle of Cola isn’t exactly “cool”. Seeing them scuttling along the kitchen floor at a top speed of 2 metres per second in the large Periplaneta americana and leaving their distinctive odour on some plates they might have run across at night isn’t very pleasant either and yet, there is some information about them which is not entirely negative.

First of all, despite their less than positive reputation, they are not know to carry or transmit diseases; they neither sting nor bite and amongst several cultures in various countries cockroaches and their egg cases are a part of the traditional armamentarium to combat certain diseases and dysfunctions. In the year 2000 E.M. Costa-Neto and M.V.M. Oliveira published an article in the journal Human Ecology Review, titled “Cockroach is good for asthma: zootherapeutic practices in NE-Brazil”; the world’s largest cockroach farm is breeding 6 billion cockroaches a year, using artificial intelligence to manage a colony larger than the world’s human population – all for medicinal uses or a source of protein for livestock feeds. There are many such cockroach breeding facilities in China, but no other matches the productivity of that in Xichang (S.W. Sichuan province). If after all this, I now report that some people enjoy eating cockroaches, fried in oil and seasoned with spices, I suppose nobody will be surprised any more.

I loved to use cockroaches in my comparative physiology course “Animal Senses and Behaviour”, because it was easy to demonstrate electrophysiological recordings with them and the fact that they “hear” with the two horn-like projections (known as “anal cerci”) at their rear end. To prepare them for the recordings is easy, as their ladder-like ventral nerve cord is accessible from the dorsal side of the animal after most of the inner organs have been removed. With two fine silver hook electrodes pushed under the connectives between two nerve ganglia, I could then carefully lift the nerve cord ever so slightly above the cockroach’s body liquid and record its nervous activity to be displayed on an oscilloscope. I then got my trombone and played short bursts of low or high frequency tones. The lowest frequencies picked up by the anal cerci elicited a train of responses in the nerve cord and showed the students that the information from the anal cerci was passing on the way to the brain of the cockroach through the ganglia responsible for leg movements. The same preparation was also useful to demonstrate the response to shadows when I passed my hand or my fingers across the insect’s eyes.  I need to add that cockroaches (and some mutations like white-eyed individuals) have been used in research on vision and visual information processing in a variety of scientific laboratories. Most roaches, are easy to breed, are undemanding, live for 6 months and some, like the Hissing Roach, even make pets.

That one can even have fun with cockroaches I learnt when I was a sailor, because ships almost always have cockroach stowaways, especially the small German species Blatta germanica. A bit of ground coffee put in a glass with butter or some other fat smeared on the upper rim of the glass’ inside would trap some of the nocturnal creatures and, competing with each other, we could find who had caught the most roaches the next morning. We also organized cockroach races to see who had the fastest insect.  Cockroach species occur in a variety of habitats (and not just in human dwellings). That there are even aquatic species that dive into a stream or pond, I only learnt recently in Northeast India, but that some species give birth to live young and feed their offspring with a kind of “milk” or that some can reproduce without males, I knew before. Having been around for about 300 million years, the cockroach “tribe” will almost certainly still be there when humans have become extinct. So: hats off and some respect to these little unwanted and unloved champion survivors. There is even a song dedicated to them: the Spanish folk song “La cucaracha” and when a cockroach would fly into our house in Jamaica (they DO fly when the temperature is well above 30⁰C), I did not kill it, but picked it up and returned it to the garden. Sounds crazy to many, I guess, but will be understandable to some (I hope).

© Dr V.B. Meyer-Rochow and, 2021.
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