Silkworm & Meteorological Environments

The influence of temperature, humidity, light, air and other meteorological factors on the life activities of silkworms. These factors influence each other and restrict each other, and have a comprehensive effect on the life activities of silkworms. The silkworm is distributed in a wide area and has many varieties, and its adaptability to meteorological factors is very different. Although the same species has different requirements for meteorological conditions in different development stages.

Temperature Silkworm is a variable-temperature animal, and its ability to maintain and regulate body temperature is not strong. Changes in environmental temperature have a direct effect on body temperature, so body temperature and environmental temperature are basically the same. However, the body temperature of silkworms changes regularly with the progress of the silkworm instar. Under the same environmental conditions, the body temperature of the large silkworm is higher than that of the small silkworm, and the body temperature of the middle-aged silkworm at the same instar is lower. The body temperature of silkworms increases with growth, reaches the highest point of body temperature at that instar at extreme growth, and then drops again. This change in body temperature that occurs with development is related to the change in the body surface area of ​​the silkworm body per unit weight, that is, the smaller the body surface area, the more difficult it is to lose body temperature, and the higher the body temperature.

The normal metabolic process of silkworms can only be carried out at a certain temperature. Changes in temperature can accelerate or inhibit the metabolic process, or stop the metabolic process completely. Within a certain temperature range, as the temperature rises, the mulberry leaf food intake, digestion and absorption and defecation per unit time increase; the number of dorsal tube beats increases and blood circulation speeds up; the breathing is vigorous, and the carbon dioxide exhalation increases. , Obviously promotes the various physiological functions of silkworms, and keeps the various metabolic processes in the body in a coordinated state. The influence of body temperature on the metabolic process actually works through the influence on enzymes, and enzymes are extremely sensitive to temperature.

The temperature range for silkworm development is roughly 7-40℃, and the physiological optimum temperature for normal larvae development is 20-30℃. In this temperature range, the growth is generally better, the growth rate increases with the increase in temperature, and the time required for development is reduced. But living in a low temperature below 15°C, the behavior is sluggish, and the growth is slow; the instar of feeding at 35°C is prolonged instead. It can be seen that temperatures below 20°C and above 30°C are not suitable for the physiology of silkworms, and long-term exposure is harmful to the health of silkworm bodies.

Within the physiological temperature range of larvae, different breeding temperature must be determined according to the characteristics of silkworm species and instar, feed quality and other meteorological factors, in order to make silkworms grow well, have strong vitality, and produce cocoons. High, good silk quality, in line with the requirements of physiology and life. For example, small silkworms are suitable for breeding at higher temperatures. The first to second instar is 26 to 27°C, and the third to instar is 25 to 26°C. It develops quickly, and increases in food intake, digestion, and body weight. In the future, the weight of the whole cocoon and the weight of the cocoon layer will also be heavier; It is suitable for low temperature feeding. In case of high temperature, the food intake and digestion will be small, and the weight of the whole cocoon and the weight of the cocoon layer will be low. However, the resistance to low temperature of 4th-year-old is weak, and the temperature should be 24～25℃. If the temperature is below 20℃, the weight of the cocoon will be reduced after a long period of time and stunted growth, while the 5th instar will be raised at low temperature of 20℃ or below. Although it can promote the synthesis of silkworm tissue protein and increase the weight of silkworms, the amount of silk protein synthesis is relatively reduced. Feeding at a high temperature of 24℃ or above will promote the synthesis and secretion of silk protein. Therefore, the 5th instar feeding temperature 23～24℃ is suitable. In the same instar, the feeding temperature should be higher during the low-eating period and mid-eating period, while the full-eating period and sleeping period should be lower. In addition, the breeding temperature of silkworms should be lower than that of hybrids. European varieties are lower than Japanese varieties, and Japanese varieties are lower than Chinese varieties. The monomorphism is lower than the dimorphism, and the dimorphism is lower than the diversification; the mulberry leaves given should have a higher hardiness within the appropriate temperature range, while the tender leaves should be appropriately reduced.

Humidity directly affects the evaporation of silkworm body water, the regulation of body temperature and respiration, and indirectly affects the nutrition of silkworms through the withering of feed. At the same time, it is related to the dryness and wetness of the silkworm seat and the reproduction of pathogenic bacteria. When the humidity increases, the silkworm body has difficulty in evaporating water, the body temperature rises, the breathing volume increases, the pulse rate increases, the food intake and digestion volume increase, and the instar period shortens. However, high humidity often causes the body of silkworms to become hypertrophy and reduce their health. If high humidity is combined with high temperature, it will increase the harmfulness of high temperature to silkworms; while reducing humidity can reduce the harmful effects of high temperature. When the humidity is low, although the silkworm seat is in good hygiene, the mulberry leaves given are easy to wither, which affects the moisture content of the silkworm body, especially in the young silkworm stage, causing the silkworm to fall into malnutrition. After prolonged, it often causes it during sleep. Difficulty in molting.

Silkworms have a certain ability to regulate water, mainly obtain water from feed, and evaporate in a gaseous state through the valve and body wall. Or excreted with feces in the form of silkworm urine through excretory organs. The evaporation of water from silkworm bodies is also restricted by humidity. Under excessively dry conditions, if the water intake and excretion are not balanced, the water content of the silkworm body will decrease, the blood osmotic pressure and pH will increase, which will hinder the progress of material metabolism, and the silkworm will grow poorly and become weak. If the humidity is too high, especially when eating feed with a lot of water, the water in the silkworm body is not easy to evaporate through the air valve or body wall, and the excess water is mainly discharged in the form of silkworm urine. While urinating a lot, the body loses a lot of salts, which lowers blood osmotic pressure and blood pH, which makes it easier to weaken the silkworm body. For silkworm species with high silk weight, the silkworm body will become hypertrophy and blood acidity will increase, which will cause nerve paralysis and induce non-cocooning silkworms.

The moisture content of the silkworm body is roughly due to the low moisture content of the silkworms when they hatch, about 76%. After eating mulberry, the moisture content rises rapidly. After harvesting the ants, it is nearly 85%, and it will increase by 2 to 3% when it sleeps. From 2nd instar to 4th sleep, the moisture content of silkworms stabilized at around 87%. The moisture content of 5th instar silkworms decreased slightly in the first two days, and then began to decrease rapidly on the third day. When the silkworms were mature, they fell to the level of ant silkworms. Therefore, in the production of silkworms, the first instar is more humid and the fifth instar is dry. Generally, the suitable humidity for feeding is 80-90% for the first instar, and then decreases by 5 to 6% for each instar. When it reaches the fifth instar, the relative humidity is 60-70%. Feeding and breeding should have corresponding changes due to different silkworm species, weather and feed conditions.

Air The air contains oxygen that is indispensable for silkworms to breathe, as well as harmful gases such as carbon dioxide, carbon monoxide, ammonia, and sulfur dioxide that are harmful to silkworms. Due to heating and burning, fermentation of sand, the respiration of silkworms and mulberry leaves, and the breathing of breeders, oxygen is constantly being consumed in the silkworm house, and undesirable gases such as carbon dioxide, carbon monoxide, ammonia, and sulfur dioxide are constantly increasing, which hinder the respiration of silkworms. Poor growth and development will damage the health of silkworms. Therefore, especially in the large silkworm stage, necessary ventilation should be carried out in the silkworm room. Small silkworms have a large respiration per unit body weight, and they also need to pay attention to breathing when they are more confined and concentrated.

As the concentration of carbon dioxide in the air increases, the opening and the number of opening and closing times of the silkworm body’s valve will change. When the carbon dioxide concentration reaches 4%, the valve opening will reach 100%, which will increase the amount of water evaporation from the silkworm’s body and affect material metabolism. Growth and development and cocoon quality have adverse effects; for example, intestinal juice will be spit out when the concentration of carbon dioxide is close to 12 to 13%, and death will be caused by continuous exposure to carbon dioxide of 15%. When the carbon monoxide in the air exceeds 0.5%, the activity of the respiration enzymes of the silkworm body is obviously inhibited, which affects the normal progress of the oxidation in the tissue cells. When the ammonia content in the air is 0.05%, in addition to the poisoning effect on silkworms, it also has similar adverse effects as carbon dioxide. When the content of sulfur dioxide in the air is between 0.1% and 0.2%, it is harmful to silkworms and makes the cocoons uncomfortable. In addition, indole produced from silkworm dung, residual mulberry and silkworm carcass is highly toxic to silkworms. Exposure to incompletely burned oak smoke can cause silk gland abnormalities. Silkworms will have symptoms of poisoning if they eat mulberry leaves or fluoride poisoned by fluoride, which will increase the number of dead silkworms.

Carbon dioxide, carbon monoxide, sulfur dioxide and other undesirable gases are also toxic to silkworm eggs. Most of the poisoned silkworm eggs have dead eggs or uneven hatching in the late stage of incubation. Exposure of silkworm eggs to tobacco, other drugs, and certain volatile gases not only cause breathing problems, but also because the poisons attached to the surface of the egg shells are eaten down with the egg shells during incubation, causing poisoning.

Proper airflow can not only eliminate the undesirable gas generated in the room at any time, but also promote the evaporation of moisture from the silkworm body and lower the body temperature. In the young silkworm stage, mulberry leaves, silkworms, and snails emit less harmful gases. The silkworm bodies are small, and water and heat are easily lost. Only proper micro air flow is needed. Otherwise, it will be difficult for the silkworm house to keep warm and moisturize, and the mulberry leaves will become dry. The growth and development of silkworms is unfavorable. The silkworm stage requires a larger airflow, especially in the full-feeding period or high temperature and humidity, the airflow can eliminate steaming heat, help the water evaporate from the silkworm body, promote the decline of body temperature, and reduce the hazards of high temperature and humidity. In a normal feeding environment, it is generally appropriate to have an airflow of 0.1 to 0.3 m/s. When the mature silkworms form cocoons, large amounts of water and other undesirable gases are discharged due to defecation, urination, silking and cocoon formation. Attention must be paid to the air circulation. This not only makes the indoor air fresh, but also reduces dead cocoons and no cocoons. Silkworms can also remove moisture and improve the quality of cocoon silk.

Light The response of silkworms to light is phototaxis. Generally, the ant silkworm has a positive phototaxis in the range of 5-100 lux (Lx), and the most prominent when it is 15-30Lx. With the growth of silkworm instar, the required light intensity gradually decreases, and mature silkworms have the strongest tendency to weak light of 13Lx. In an instar, the phototaxis of the silkworm is the strongest, and the dormant silkworm is the weakest. But in strong light above 100Lx, both small silkworms and large silkworms showed negative phototaxis.

The light affects the action of the larva, and its action is related to eating mulberry. Under light conditions, the phototaxis makes the silkworm move to the upper layer of the silkworm seat, which not only prevents the occurrence of the silkworm, but also eats fresh mulberry leaves, which provide good nutrition and develop faster.

Light has an inhibitory effect on the development of silkworms, which is more obvious at high temperatures, but gradually disappears with the growth of silkworm instar. Light also has a certain inhibitory effect on growth. At 5th instar, the weight of silkworms raised in continuous darkness is heavier, but expressed in terms of total cocoon volume. Regardless of whether the large silkworms are reared with light or not, they are all bred with illumination at the small silkworm stage. The amount of cocoon is heavy. The reason is that the small silkworm stage lighting makes the silkworms develop in a uniform direction, so that the whole instar is prolonged, so the final weight expressed by the total cocoon weight. The photoperiod also affects the development of the larvae. The full-day light is longer than the full-day darkness. Those who have continuous lighting for 6 to 9 hours within 24 hours a day pass the shortest time.

The light of the silkworm chamber is generally scattered light, which is suitable for the natural state of twilight during the day and darkness at night. Polarized light and direct light will cause uneven distribution of silkworm heads and uneven development. At the same time, the local temperature of direct light will increase, which will accelerate the withering of mulberry leaves. When the mature silkworm has strong backlight, it is necessary to darken the upper bobbin and make the light even, so that the thickness of the cocoon layer is uniform and reduce the occurrence of double palace cocoons.

Light also affects the development speed of silkworm egg embryos. The embryo develops faster when the silkworm eggs are illuminated before the green is turned on, but the opposite is true when the silkworm eggs are turned on. The embryo develops faster when it is dark. If the silkworm seeds are shielded from the dark, the embryos that develop slowly can accelerate their development in the dark environment, and the embryos that develop faster when they reach the stage of ant emergence, hatching is inhibited due to the darkness, which can promote uniform hatching.

Silkworm eggs hatch and moths have daily rhythms that appear 24 hours apart. If the silkworm eggs or silkworm chrysalis are protected in an environment that is always bright or dark day and night, this daily rhythm will be destroyed, and the hatching and emergence will be uneven, and there will be no obvious peak of hatching and emergence in a day.

Artificial feed breeding has different requirements on the meteorological environment from mulberry leaf breeding; the temperature during the breeding of small silkworms with artificial feed generally requires 28-30°C, which is lower than 25°C and has poor feeding performance and significantly poor growth; humidity should be kept within the range of 85-90%. If the humidity is small, the moisture content of the feed will drop quickly, which will affect the amount of food consumed. The humidity during sleep should be reduced to about 65% to improve the hygiene of the silkworm seat. The light conditions have a greater impact on the artificial feed breeding effect. Long light will prolong the instar and weight. , Cocoon weight and cocoon layer weight increase, but it is easy to cause oxidative deterioration of feed, uneven distribution of silkworm heads, uneven dormancy, and increase in silkworm reduction rate. Therefore, dark feeding is generally adopted. Under high temperature (28°C) conditions, long light or full-bright feeding can make four-sleeping silkworms three-sleeping, while under low-temperature (22°C) conditions, long-lighting or full-blooming is easy to do five dormancy. Illumination conditions in feeding also have a significant impact on chemistry. Short light produces more diapause eggs than long light.