Non-cocooning Silkworm Larvae

Diseased silkworms that do not spin or cocoon due to physiological and pathological reasons. Commonly seen non-cocooned silkworms have no obvious symptoms before they mature, but they do not form cocoons after being swarmed. Some spit out a small amount of floating silk or flat silk, and later become naked pupae or die. The causes of non-cocooned silkworms are: silk gland abnormalities and physiological dysfunction of silkworms, silkworm nerve paralysis, silkworm disease, poor feeding and poor environment in the swarm, etc.

In silkworms, the growth of silk gland cells is small and the arrangement is uneven, so that the silk glands grow poorly, even partially or completely atrophy; some silk glands have underdeveloped nuclei, and there are still very few branches of the nuclei at the end of the 5th instar, or because of the silk glands. The trachea is less distributed, or because the silk gland grows too hypertrophy, it oppresses the trachea at the head-thoracic state, causing insufficient oxygen supply to the cranial ganglia, and thus the brain’s cocooning central function is impaired. Some are due to the discordance between the spinning exercise and the dehydration of liquid sericin, and the viscosity of sericin is too high or too low, which affects the fibrosis of the silk material; some due to endocrine disorders, the metabolism of silkworms is imbalanced and affects the silk glands. Some are abnormal silk glands. Due to the degeneration of local silk glands, the central silk glands are abnormal, which affects the production and movement of silk materials, causing the silk glands to swell and rupture, and the silk materials flow into the body cavity and become black and solidified. , And finally died; some were blocked due to the malformation of the spinning tube, which hindered the spinning. If most of the silk material cannot be spit out, the poisoning and death occurred due to excessive amino acids. The occurrence of non-cocoon silkworms is also related to silkworm species. Generally, there are more silkworms without cocooning silkworms, and some varieties are weaker and more prone to occur.

The silkworms are exposed to trace amounts of pesticides (less than the lethal medium amount) during feeding, which paralyzes the central nerves of the silkworms. The silkworms do not show symptoms of poisoning at first, and then the pesticides continue to accumulate in the body and cause physiological disorders, which are manifested as poor growth and development, and physical weakness. Resistance to diseases is reduced, and non-cocooning silkworms occur. After 5 years of middle-to-late pesticide poisoning, the appearance of symptoms is not obvious, but it is not lively and poor focus on the stalk. After half a day to a day in the stalk, it still crawls around, crawling and spinning, without spinning. Certain rules can not make a normal cocoon, or form an irregular cocoon, but most of them cannot pupate and die. Non-cocooning silkworms are prone to occur during the 5th instar full feeding period.

The silkworm diseases that cause non-cocooning silkworms mainly include pus disease, micronosis, and softening disease. Their harmful effect is to directly invade the silk glands and severely destroy the secretory function of the silk glands. At the same time, pathogenic microorganisms multiply in the silkworm body to take nutrients and affect the development of silkworms and the growth of silk glands. In addition, pathogens often produce a large number of toxic metabolites when they are parasitic in the body, which paralyzes the central nervous system of silkworms and loses regulation of silk spinning function.

Poor environmental conditions and feeding management often lead to the occurrence of non-cocooned silkworms. During feeding, high temperature and humidity, low temperature and humidity, poor ventilation, too much carbon dioxide in the room, and insufficient oxygen supply; or due to the urination of mature silkworms, the air is polluted, and the breathing of mature silkworms is affected, causing physiological abnormalities and nerve paralysis. Too high humidity will often cause the silkworm endocrine disorders to cause abnormal silk glands and lose the ability to spin silk cocoons. The temperature of the upper cluster cocoon is low, which affects the silkworm’s spinning function, inhibits the spinning movement, and promotes the occurrence of non-cocoon silkworms. The humidity in the 5th-instar scorpion is too high, and it is easy to grow without cocooning silkworms. The density of the cocoon is too dense, and the mature silkworm cannot find a proper cocooning position. In addition, the humidity in the cocoon makes the non-cocooning silkworm more serious. When the leaves are too tender, especially the 5th-instar leaves, the water, protein (amino acid) and acidic substances in the blood increase, which leads to changes in the blood characteristics of silkworms, causing nerve paralysis and non-cocooning. Similarly, the air in the swarms at the end of the 5th instar is dirty, especially the stimulation of camphor, alcohol, garlic, formaldehyde, and factory waste gas that can cause nerve paralysis, inhibit the spinning function, and cause non-cocooning silkworms. When using juvenile hormone at 5th instar, due to improper dosage and period, it disturbs the balance of physiological functions of the silkworm body, and non-cocooned silkworms often appear.

The measures to prevent the occurrence of non-cocoon silkworms are: carry out silkworm disease control, thorough disinfection, and eradicate pathogens; strengthen breeding and cluster management according to the different characteristics of silkworm species; prevent pesticide poisoning; and frequent air exchange in the silkworm chamber and the upper chamber. Keep the air fresh and clean.