Introduction of cockroaches
The morphology of cockroaches
Cockroaches belong to Insecta and have lived on the earth for 280 million to 320 million years. They are fossil animals. There are 3,500 known species of cockroaches (there are also 5,000 reported species), both domestic and wild. Wild species account for the vast majority, mostly living in grass, litter, gravel or bark, and also living in nests such as ants, termites and bees, and generally have little to do with human beings. Domestic species account for about 0.5% of this project, mainly belonging to Blattella, Eupolyphaga and Eupolyphaga. There are 13 species known in China. At present, the common cockroaches are Blattella germanica, Periplaneta americana, Periplaneta australis, periplaneta fuliginosa, Periplaneta fusca and so on.
Cockroaches vary in size (2-90 mm) and color. Cockroaches have a flat body with oily luster, and the rear plate of the abdomen has openings for secreting glands, and the secreted liquid has a foul smell. On the head of a triangle, there are two small monocular eyes and a pair of big compound eyes. The two upper jaws are fan-shaped, overlapping like scissors, and there are nodules between the teeth, which are like vises when crushing hard objects. The mouthparts are primitive chewing, with a hard upper jaw, five lower jaws and three lower lips. There are four tentacles and many short hairs on the mouth. Tentacles are tools for it to collect food, and short hairs are taste and smell organs with sensory nerves on them, which can feed or avoid toxic bait. Cockroaches can climb walls and have small claws on their legs for climbing walls. Nerve endings on the joints of the legs are very sensitive and can detect slight vibrations. The tail whisker at the end of the tail is a complex vibration receptor, which can sense the direction of external stimuli. Well-developed, suitable for sprinting, can run three miles an hour, and can swim. Cockroaches' antennae have a very sensitive sense of smell, and they can identify their own species by smell.
Second, the reproduction and growth of cockroaches.
The ⅹ dorsal plate of the abdomen of male and female insects is called the anal superior plate, and there are 1 pairs of caudate whiskers on both sides of its base. The female ⅶ ⅷ and the male ⅸ ⅷ are called the lower reproductive plate. There are 1 opposite spines (abdominal spines) on both sides of the end of the lower reproductive plate of male worms, which is an important feature to distinguish male and female adults.
Male and female adults can mate about a week after emergence. Males can mate many times in their lifetime, while females only mate 1 or twice. 1 mating can make them produce fertilized eggs for life. Female cockroaches are not picky: According to a recent analysis of the sex of cockroaches, when the reproductive peak begins to decline, the female cockroaches will be less picky about male cockroaches. Therefore, female cockroaches will prefer male cockroaches, and female cockroaches will maintain their willingness to mate with male cockroaches for life. Some cockroaches mate three to five times in their lifetime, but they can only mate once and remain pregnant for 40 days before the next mating.
Female insects lay eggs in special colloidal capsules, forming egg sheaths (egg pods). The egg sheath is produced by female insect secretion, which is smooth and hard, has waterproof function and can protect the development of its endosperm.
Unmatched females can also produce egg sheaths, but generally they cannot hatch nymphs. However, some species such as Periplaneta americana and Periplaneta saccharum have parthenogenesis, that is, females can produce fertile eggs without mating.
The behavior of cockroach spawning sheath varies from species to species. There are three main ways for cockroaches to stay indoors: 1,1-Two days after laying their eggs, the female chooses a relatively hidden place, first bites out a depression on the surface of the object, spreads the egg sheath inside, and then covers the egg sheath with sticky saliva. Sometimes the egg sheath is directly adhered to the habitat with saliva, such as cabinets, wooden (paper) boxes, table corners or sundries. This kind of egg sheath contains enough nutrients to meet the needs of embryo development. Periplaneta americana, periplaneta fuliginosa, etc. Lay eggs in this way; 2. After the female gives birth to the egg sheath, she drags it at the abdominal end until the nymph will hatch from the egg sheath and then fall off from the mother before giving birth. In the development process, the embryo in the egg can get the necessary water and nutrition from the mother, and the egg sheath is carried by the mother worm, which can be better protected. If the egg sheath falls off prematurely, the eggs inside will not hatch. The oviposition mode of Blattella germanica belongs to this type; 3. Female insects first produce thin and soft egg sheaths and lay eggs in them. After laying eggs, the egg sheath shrinks into the "nursery" in the body and remains until the nymph hatches. This is a viviparous cockroach. The oviposition mode of sugarcane borer belongs to this type.
Cockroaches are gradually metamorphosed insects, and their whole life cycle includes three stages: eggs, nymphs or adults.
1, egg stage
The eggs are narrow and long, milky white and translucent, and arranged in two neat rows in the egg sheath. Suture of fetal head hole. When hatching, the nymph pushes upward, causing the closed egg sheath seam to crack and escape. The number of eggs in the egg sheath ranges from a few to more than 50. The egg sheath is hatched at 25℃ and the relative temperature is 60-80%, and the egg period is about 28-90 days.
2, nymph stage
Nymphs just hatched from the egg sheath all gather around the egg sheath, showing white color, and then gradually darken and spread out. Nymphs are similar in appearance to adults, but they are small, wingless and have immature sex organs. Nymphs develop slowly. It must undergo molting several times and grow up gradually, and the number of tentacles and tails also increases with age. After the nymph molts for the last time, it will grow wings and emerge as an adult. The newly molted nymph and newly emerged adult are also white, and then the color gradually darkens. The nymph stage is long, generally lasting about 30-450 days. After losing appendages or damaging antennae, nymphs can molt and regenerate at the next age.
3. adulthood
Six common adult cockroaches all have developed or undeveloped wings, which can be distinguished from nymphs.
Male and female adults can be easily distinguished by external morphology: male cockroaches have two pairs of appendages at the tail, 1 segmented tail whiskers, 1 tiny spines (abdominal spines); The female cockroach has only 1 pair of appendages in the tail, that is, the tail whiskers, without spikes; Male cockroaches are generally thin and slender, while female cockroaches are thick and wide; In a few species, the wings of male cockroaches are developed and extend to the tail end, while the wings of female cockroaches only cover the first half of the abdomen or have no wings.
A characteristic of cockroach's life history is its long cycle. Take Blattella germanica with the shortest cycle as an example, it usually takes more than two months to complete a generation, and Periplaneta americana with the longest cycle exceeds 1 year.
Adults also live a long life. The shortest life span of Blattella germanica is about 100 days, and the longest life span of Periplaneta americana is 1 year.
From nymph hatching to the end of adult life, the life span of cockroaches is very long, generally about 2 years, up to 3 years and 200 days at the shortest.
A fertilized female cockroach will produce a large number of egg sheaths in her life, and Periplaneta americana can produce more than 50 at most, so cockroaches are very fertile. A mature female cockroach can produce an egg sheath containing 14-40 eggs every 7- 10 days. The egg sheath is colloid, and the incubation temperature is 20℃-37℃. The higher the temperature, the shorter the incubation time. Constant temperature of 30℃ only takes 20-30 days, and the longer one can exceed three months. A female cockroach can breed nearly 10,000 offspring a year, up to100,000 at most.
Thirdly, the regularity of cockroaches' inhabitation, activity, diffusion and appearance at night.
Cockroaches like to live in warm, humid, food-rich and crevice places, which are the four basic conditions for their reproduction. These conditions can generally be met in buildings where people live and live.
Cockroaches love warmth and tide. In restaurants, families, trains and ships, the kitchen is always the most seriously violated place. In the kitchen, they like to live near the stove and the pool.
Cockroaches like the dark and fear the light. They lie down during the day and go out at night. Hide in dark places during the day, such as furniture, cracks in walls, corners of caves, sundries, etc. At night, especially after lights out, people go out for activities, foraging and looking for spouses. In 24 hours a day, about 75% of the time is resting.
Cockroaches are flat, suitable for drilling and hiding holes, and can be hidden in narrow gaps. For example, the adults and nymphs of Blattella germanica can hide in the gap of 1.6 mm, and the females with eggs can also live in the gap of 4.5 mm wide. When perching in the crevice, the feet are close to the body, the tail whiskers extend horizontally or contact with the supporting surface, and the tentacles often extend outward and wave from time to time to keep alert.
Different kinds of habitats are different. Blattella germanica is common in all kinds of cracks, such as cracks around pipes, walls, partitions and floors. Periplaneta americana likes to live in big holes and prefers hot and humid environments, such as fermentation workshops and bean products processing plants in breweries, and often lives in cool wells, sewers and basements in groups. Periplaneta fuliginosa is more common in the corner under cupboards, tables and pools.
In winter, most people live in the kitchen and live and move near heat sources such as stoves and radiators. In the hot summer, the kitchen temperature was too high, so it was scattered and moved to other places.
Cockroaches like to live in groups. In a habitat, as few as a few, as many as dozens or hundreds gather together, all because of the lure of pheromones. Both adults and nymphs of cockroaches can secrete an aggregation pheromone, which is secreted by rectal pad and excreted with feces. Brown spots on feces are common where cockroaches live. The more feces, the more cockroaches gather. It is an important measure to do a good job in hygiene and remove the traces of cockroaches.
Cockroaches spread in two ways: active diffusion and passive diffusion:
Active diffusion: spread to different places by crawling or sliding. In order to find a suitable habitat and necessary living conditions, including temperature, humidity, food and hidden places. In the case of low room temperature, cockroaches mostly migrate to gaps around the stove or gather in warm environments such as heating ditches. In hot summer and hot season, you can glide for a long time and hide in a cool place to avoid overheating. In order to get moisture and proper humidity, there are activities to get wet: at night, climb into the sink, cluster around the bucket, or stop on the water pipe. Indoor cockroaches can spread to neighbors through holes in walls and gaps in doors and windows.
Passive diffusion: In today's era of increasingly developed and frequent traffic, this diffusion mode is particularly prominent. The train was badly damaged by cockroaches. The intrusion rate of sleeping cars can be as high as 40%, and the dining car is higher. Baggage, luggage and other items carried by passengers, as well as checked items, may bring cockroaches on the train. Cockroaches on trains can be taken away by passengers and goods. With various means of transportation, cockroaches have traveled all over the world.
Cockroaches lie dormant at night, hide during the day and move at night;
It was observed that Blattella germanica started its activity at 19, with a peak at 2 1-22, and a small peak appeared at 2: 00 am the next day and disappeared at 5: 00. Periplaneta fuliginosa started the activity on 19, with a peak at 20: 00, two small peaks at 23: 00 and 2: 00 the next morning, and the activity ended at 4: 00 a.m.
It was also observed that the activity of Periplaneta americana in 12 hour alternate day and night environment can be divided into six periods: 1 period: before the darkness began, the activity level began to rise; Stage 2: after the darkness begins, the activity increases obviously; The third stage: the peak period of activities, lasting 2-3 hours; The fourth stage: the activity suddenly drops; The fifth stage: in the second half of darkness, the activity is still low; The sixth stage: 5 hours after dawn, or there is still a low level of activity, or completely at rest.
Fourth, the cockroach's food
Cockroaches are omnivorous insects with a wide range of feeding habits. All kinds of food, including bread, rice, cakes, vegetarian and cooked food, melons and fruits, drinks, etc. I especially like delicious, sweet and oily pasta. Cockroaches are addicted to oil. Among all kinds of vegetable oils, sesame oil is the most attractive, and some places call cockroaches "oil thieves". Among sugars, brown sugar and maltose are the most attractive. Cockroaches often eat other things, such as cotton wool products, leather products, paper, books, soap, wires and so on. In outdoor garbage dumps, sewers, toilets and other places, eat rotten organic matter, and even kill animals.
Different kinds of cockroaches also have different feeding habits. Blattella germanica likes to eat fermented food and drink, and likes to drink beer. Periplaneta americana likes to eat rotten organic matter; Periplaneta australis mainly feeds on plants.
Water is more important than food for the survival of cockroaches. Cockroaches are thirsty and hungry. They can't drink water for one month and eat for three months (with water). Under the condition of feeding Periplaneta americana dry food without water, the female worm can survive for 40 days and the male worm can survive for 27 days. On the other hand, if there is water and no food, females can live for 90 days and males can live for 43 days. Cockroaches can survive for a week without their heads. The headless cockroach died of thirst because it had no mouth to drink water.
When there is no food and no water in harsh environmental conditions, cockroaches will eat each other, eating small and weakly, especially insects that have just molted, and their skin is tender, becoming prey for food and absorbing the water in the corpse to survive.
Verb (abbreviation for verb) describes the growing prosperity of cockroaches.
Due to the development of urbanization, dense population, abundant food, more buildings, convenient transportation and rapid increase of logistics, it provides an ideal environment for cockroaches. At the same time, the indoor environment is constantly improving. The widespread use of air conditioners, home decoration and heaters provide a good wintering environment for indoor cockroaches, so there are more and more indoor cockroaches. Around 25℃ is the best activity period for cockroaches. The more modern the city, the easier it is to breed cockroaches. For example, Blattella germanica is most active at room temperature of 24℃ to 32℃, and computers, fax machines, distribution boxes, DVD players, communication equipment, refrigeration equipment, instruments and other places become the best habitats for cockroaches (called "household appliances pests"). Its body is very small, the adult is only about 1.2 cm long, and it can climb into the machine to reproduce. Its excrement and shelling will seriously pollute the machine and even cause short circuit. According to the analysis, the main reason for the proliferation of Blattella germanica in the office building is that employees eat in the office, and many people like to eat snacks in the office, so it is difficult to clean up biscuit crumbs and potato chips. In addition, there are many documents in the office, which are generally not allowed to be cleaned by cleaners, and the accumulation of debris has formed a hotbed of cockroaches. Blattella germanica breeds quickly, and it only takes 60 days for a generation. After repeated spraying, the residual cockroaches are easy to form drug resistance, and the power of ordinary cockroach killer is limited, so it is impossible to spray liquid cockroach killer in precision machines such as computers and fax machines. These cockroaches have become one of the three most drug-resistant pests in the world.
The first place to control cockroaches should be restaurants, hotels and food processing industries, where people come and go, the temperature is suitable all year round and food is sufficient, which provides excellent conditions for the survival and reproduction of cockroaches, followed by hospitals, families, office buildings and large computer rooms, where the density of cockroaches is the highest. Dark corners, such as kitchens, food cabinets, feed banks and toilets, which are not easily noticed by people, have become hiding places for cockroaches.
Blattella germanica is becoming the dominant population. Blattella germanica is mainly yellow and purplish red, much smaller than Periplaneta americana, and the smallest is as big as mung bean. It likes warmth, wide distribution and fast reproduction, and its activity is closely related to temperature. It is most active at 24 ~ 32℃. The nymph lasts for 3 ~ 65438 02 weeks, survives for 4 ~ 9 months at 20 ~ 29℃ and for 2.5 months at 30℃. In addition to the usual places, cockroaches also like to move around in the office computers, photocopiers, power outlets and other places, and live in thousands of small gaps in family beds, ceilings and even windowsills and doors. It can go without eating for a month, and generally hides in some places with small gaps to enter the family, such as packaging cartons. Blattella germanica likes drinking beer.
Six, cockroaches and spread diseases
Cockroaches can eat almost anything, bite babies' skin and fingers, and get into people's ears to cause ear diseases. They also eat feces, sputum and animal carcasses. Excretion while eating, carrying germs, polluting food and spreading various diseases. It has been proved that cockroaches can carry about 40 kinds of bacteria that are pathogenic to vertebrates, such as leprosy, Yersinia pestis, dysentery and Shigella, Staphylococcus aureus that causes boils, Pseudomonas aeruginosa that causes urinary tract infections, Escherichia coli that causes urogenital tract and intestinal tract infections, and various Salmonella that spread intestinal diseases and gastritis, such as Salmonella Typhoid B and Salmonella Typhoid. Cockroaches can carry a variety of pathogenic bacteria that cause food poisoning, such as Pseudomonas aeruginosa and Escherichia coli, as well as Clostridium perfringens and Streptococcus faecalis. In addition, cockroaches can also be artificially infected with bacteria that cause diseases such as cholera, pneumonia, diphtheria, gangrene and anthrax in Asia. Cockroaches can carry many kinds of eggs, such as roundworms, hookworms, tapeworms, roundworms and whipworms. They can also be used as intermediate hosts for many nematodes, such as Echinococcus moniliforme, Hymenolepis brevis and nematodes. Cockroaches can also carry many kinds of protozoa, among which four kinds of protozoa are pathogenic to humans or animals, such as amebic dysentery and Giardia. Cockroaches can carry, preserve and excrete viruses, including Coxsackie virus and polio virus. Cockroach secretions and feces also contain a variety of carcinogens. Cockroaches can also carry fungi. A variety of fungi were isolated from cockroaches caught indoors, including a large number of Aspergillus flavus. Although cockroaches carry a variety of pathogens, it is generally believed that pathogens cannot reproduce in their bodies and belong to mechanical transmission media. However, due to their wide invasion range and miscellaneous eating habits, they can move in garbage, toilets, bathrooms and other places, and can also eat food, so they can not be ignored in causing intestinal diseases and the spread of parasitic eggs. Cockroaches produce smelly secretions, which spoil the taste of food. Sensitive people will have allergic reactions when they come into contact with food or dust contaminated by cockroaches.
Cockroaches are no less harmful than mosquitoes, flies and mice, and are one of the most difficult pests to control. Due to the continuous improvement of people's living conditions in recent years, the sealing and sanitary conditions of houses have been greatly improved, and the biological species such as flies and mice, which used to be regarded as the first pests, are also decreasing year by year. Because of this, the living conditions of cockroaches are getting better and better. As long as there is a gap of 1.6 mm, cockroaches can walk freely, and their bodies, secretions and feces carry a large number of pathogenic bacteria. In addition, it is difficult to control cockroaches, and chemical cockroaches have indirect harm to human health, so cockroaches have become the primary pests that threaten human health.
Seven, the limitations of chemical agents to kill cockroaches
To prevent and control cockroaches scientifically, besides improving the environment, preventing cockroaches from invading, indoor and outdoor sanitation, cleaning up sundries, removing garbage, plugging holes and seams, and managing drinking water to interfere with the living conditions of cockroaches (food, water and hidden places), chemical agents (pesticides), biological cockroaches and physical cockroaches can also be used.
Generally, most pesticides sold in the market are chemical pesticides, including drugs prepared by professional insecticidal companies, and also belong to chemical drugs, such as sprays, poison bait, fumigants, poison tablets, cockroach-killing chalk and so on.
The extensive use of chemicals not only kills cockroaches, but also causes environmental pollution, the residue and accumulation of chemicals and the environment that threatens human survival. Repeated use of pyrethroid chemicals for many years has made cockroaches extremely resistant to drugs. The place where cockroaches often move is also the place where humans live, live and store food. Using chemical drugs to kill cockroaches may directly threaten human health.
Chemical medicine itself has the defect of treating the symptoms rather than the root cause. In addition to the existing drug resistance of cockroaches, cockroaches and egg sheaths hidden in caves and crevices cannot be killed, resulting in missed inspection. Coupled with the drug resistance of insects, cockroaches cannot be eradicated, and the density of cockroaches can only be reduced for a period of time but will soon rebound.
At present, the drug resistance of cockroaches has increased dozens of times or more. According to experiments, cockroaches will be revived in 4-6 hours after being sprayed with a commercially available sprayer, but what they saw at that time was only suspended animation. Therefore, we can only further increase the concentration or dosage of drugs, which will accelerate environmental pollution and endanger human health.
Chemical pesticides often used in life are mostly spray-type, which is very harmful:
Most of the sprayed medicine can stay. Toxic substances first float in the air, and then fall into every corner of the room, including food. When people enter the room, these toxic substances also infringe on human health. The perfume of chemical pesticides contains toxic substances, which will paralyze the central nervous system of the brain and cause oral mucosal diseases for a long time. The low resistance of the elderly and children leads to high incidence, especially asthma patients. Toxic substances of chemical pesticides do great harm to human sperm and affect the health of the next generation; The toxic components of chemical pesticides are not easy to degrade, which has a great impact on human living environment.
Think about it, the drug resistance of cockroaches must have increased dozens or even hundreds of times. Cockroaches have bad habits of eating and spitting. Therefore, even if they use non-spraying cockroach killing drugs, when they eat them in their mouths, they may bring poison into people's food and raw materials because of their bad habits of "showing up" and "vomiting while eating". One more thing, don't forget, cockroaches can run three miles an hour!
Note: The author has worked in Jilin Provincial Center for Health and Disease Prevention, Jilin Provincial Center for Disease Control and Prevention, Jilin Provincial Center for Health Supervision and Inspection, and Jilin Provincial Institute for Occupational Disease Prevention and Control. He is an associate professor with rich practical work experience and is more sensible about things.