Roommate under the microscope: cockroach

  Don’t always fight with the same enemy, otherwise you will teach him all your tactics. – [France] Napoleon Bonaparte
  insect evolution by natural selection constantly to deal with human new chemical weapons. The fiercer the human offensive, the faster they evolve. Such stories have been repeated in history, especially in the insects that humans want to eliminate, such as the German cockroach (one of the most common species of cockroaches).
  Every time people invent a new insecticide, only a few years, sometimes even a few months, there will be German cockroaches resistant to them. Sometimes, resistance to existing insecticides also makes them resistant to new insecticides. This means that the war is over before it starts. Once drug-resistant German cockroaches appear, they will spread, and as long as people are still using the old insecticides, they will grow and reproduce unscrupulously.
  The tit-for-tat battle between cockroaches and insecticides invented by humans is amazing. Generations of cockroaches have rapidly evolved new abilities to avoid, decompose and even use pesticides. It all starts with California on the west coast of the United States more than two decades ago. The story has two protagonists-an American entomologist named Jules Silverman and a cockroach family named “T164”.
  At a meeting, a cockroach expert told me the types of these cockroaches in one breath: “American cockroach, oriental cockroach, Japanese cockroach, pale red brown cockroach, brown cockroach, Australian cockroach, brown cockroach There are several other species.” There are thousands of species of cockroaches on the earth, most of which are not at home, nor can they live at home, but the dozen or so of the most annoying species are naturally capable of reproducing indoors. For example, several of these cockroaches are capable of parthenogenesis-females breed independently. Although those cockroaches that live indoors have some special adaptability, which is conducive to coexisting with humans, the German cockroaches are equipped with the most complete. Jules’ job is to study how to eliminate cockroaches, especially the German cockroaches.
  The German cockroach that lives in the wild is very weak and will be eaten by other animals or starve to death. They only have tenacious vitality and exuberant fertility only in places where humans live. Perhaps this is why we hate cockroaches so much. They like the living conditions we like-warm and pleasant, with the right humidity, and they like the food we like to eat. No matter what reason people hate cockroaches deeply, we have nothing to fear. Cockroaches do carry germs, but they are just like neighbors or children carrying germs. So far, there have been no reports of people getting sick because of cockroaches spreading germs, but people are getting sick all the time because of other human-borne germs. The biggest danger of German cockroaches is that they form allergens when they are denser. In order to solve this practical problem and other hazards that people imagined, we spent a lot of resources trying to eliminate them.
  It is difficult to tell when the war between humans and cockroaches began, because the carcasses of cockroaches in archaeological sites are not well preserved (at least relative to beetles). Moreover, compared with studying the biological characteristics of cockroaches, people are more willing to study how to kill them.
  The German cockroach was roughly spread throughout Europe during the “Seven Years’ War” (1756-1763) between Britain and France. At that time, people carried containers across Europe. These containers were large enough to hold many cockroaches to hide. Carl Linnaeus, the father of modern taxonomy, believes that they came from Germany. Linnaeus is a Swede, and the Swedes fought the Germanic Prussians, so he thought it was ironic to name this creature that he didn’t like “German cockroach”. By 1854, the German cockroach had appeared in New York. Now they are moving around with people of different races in boats, cars and airplanes, from Alaska to Antarctica.
  In areas where the temperature and humidity of houses and cars fluctuate with the seasons, German cockroaches and other kinds of cockroaches live in people’s homes at the same time. Where central air-conditioning is installed, German cockroaches have become powerful and other cockroaches. It’s all less. For example, until a few decades ago, German cockroaches were not common in many parts of China, but as people installed heating on northern transport vehicles, the cars were warm enough for German cockroaches, and they went north. Spread; and people installed air-conditioning on the southern trucks, the cars became cooler, and the German cockroaches spread south. After arriving there, the German cockroach found a warm or cool place in residential buildings in northern and southern China and began to multiply.
  As early as 25 years ago, when Jules was in the household goods manufacturer Gallus, the German cockroach had already exploded. He was responsible for the development of drugs to kill cockroaches, and the most effective bait on the market at that time was poisonous bait. With cockroach bait, we don’t need to spray insecticide all over the house. Americans use glucose the most. It is cheap and attractive to cockroaches. The German cockroach living in the United States has become accustomed to glucose. 50% of their food comes from carbohydrates, most of which come from glucose, and humans themselves consume a lot of glucose by eating a lot of corn syrup. We use “eat dessert after dinner” to coax children to eat well, and we also use the same sweets to lure cockroaches.
  While working at Crolux, Jules realized that something strange had happened in the apartment where his friend and field entomologist Don Beeman had dropped the poisonous bait. The number of this apartment is “T164”. Tang put poisonous bait in this apartment, but the cockroaches are not dead, they are alive and well. But when Tang brought the cockroaches from the apartment to the laboratory, they died instantly as soon as they encountered the same poison on the poison bait. Poison that can kill cockroaches in the apartment can’t kill them. Don told Jules that he felt that the cockroaches seemed too frightened to avoid the bait. Back in the laboratory, Jules tested the attraction of each ingredient in the bait to the cockroaches in the T164 apartment. Experiments show that cockroaches did not avoid the poisons, nor did they avoid the emulsifiers, binders and preservatives in the bait. Then only the sugar in the bait is left-glucose. It would be weird if they really don’t eat sugar, which means they will reject sugar, a food that cockroaches and most animals have liked for millions of years. But the fact is, these cockroaches will avoid glucose when they see the glucose. Not only do they dislike glucose, but they also hate glucose. However, they are still attracted to fructose. Jules guessed that perhaps this group of German cockroaches (later people called them “T164”) learned not to eat glucose. The clever cockroach is really invincible.
  Jules verified the hypothesis that cockroaches would learn. If cockroaches can learn, then the offspring of these cockroaches should be attracted by traditional bait. The offspring of these cockroaches were born before they had time to learn. He tested whether these cockroaches would be tempted by glucose through experiments. The result is that they are not attracted. These cockroaches are not learned, they do not like glucose when they are born. The only possible explanation is that this aversion to glucose is inherited and formed through evolution. Jules designed a simple genetic experiment to see how this aversion is inherited. He mates cockroaches that hate glucose with cockroaches that still love glucose, and then crosses the offspring with those cockroaches that love glucose. Experiments have shown that although it is not 100%, the genes that control glucose aversion are indeed dominantly inherited.
  Subsequently, Jules collected samples of cockroaches from all over the world to test their preference for glucose. In the countries and regions that use poisonous bait, from Florida to South Korea, cockroaches have evolved the characteristic of aversion to glucose, and they have evolved this characteristic independently. He tried to reproduce this process in the laboratory to see if he could artificially promote evolution. He feeds cockroaches with insecticide-coated glucose, and his observations in the laboratory are similar to those in real life: it only takes a few generations for cockroaches to develop glucose aversion.
  From a certain point of view, the story of the German cockroach is very special, and there is no such thing as a second creature. But in other respects, it is just an illustration of the story that happened to those living creatures in the house. The results of evolution are amazing, creative, and sometimes bizarre, but they are not completely unpredictable. Understanding the opportunities and corresponding challenges facing organisms is the key to predicting which direction evolution will take. In the human home, the opportunities faced by creatures include feeding on skin scraps or human food, and houses can provide shelter; while the difficulty is how to get into the house and survive the fierce human offensive.
  Under certain conditions, some organisms will quickly adapt to insecticides: these organisms have high genetic diversity; insecticides have killed almost all target organisms; insecticides are repeatedly applied to these organisms; and Competing organisms as well as parasites and viruses that harm the target organism will disappear. The German cockroach satisfies these conditions perfectly, and the same is true for the vast majority of domestic creatures that we actively want to eradicate. Therefore, organisms in human homes evolve most rapidly, but these evolutions rarely proceed in a direction that is beneficial to humans.