1971 School Magazine

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The best material for the silkworms to spin tn is trusses of hay as the silkworm can climb up into them and spin in a confined area with easy graspilg points. When a silkworm spins in the corner of the box a lot of the silk thread is wasted as floss to grasp on to the sides and not as much close packed easily removable material is produced. A silkworm spins by moving its head in a figure of eight. When a silkworm is spinning it is very important not to disturb it as if disturbed a silkworm although attempting, cannot spin again and becomes a pupa without its protective cocoon. It is also important when the silkworms are spiming to make sure that two do not spin together as the threads cannot be unwound and it is also dangerous to the pupa. As a worm several diseases are common to the silkworm. "Pepper" disease is the most deadly--and has been around as long as the silkworm' It affects the silkworm after the second moult, and affected worms appear covered with black spots. There is no cure and^most worms.die before spinning. If they do spin and become moths their eggs carry the disease. The prevention of the disease is by pasteurised eggs. Muscardine or cardine can affect the worms at any age. It is impossible to detect until a few hours before death when the worm becomes soft and flabby and a pale pink colour. Gradually the body becomes stiff and later a fine white powder appears all over the body, this is composed of a minute fungus Botrytis bassiana. The disease is very contagious and the only cure is to pick up dead worms before they become stiff and burn them. It can also be controlled with copper sulphate after the worms have spun. Falcheric is an intestinal disease and the most disappointing and dreaded one. It usually attacksjust before the worms spin. The infected worms become inactive. At death the bodies become limp and flaccid and within twenty four hours the contents turn black and putrefy. The ejections of diseased worms are semi-liquid and contain millions of microbes. There is no cure. The causes of this disease are overcrowding, hunger, bad ventaliation, fermenta- tion of the leaves and feeding wet or damp leaves to the silkworm. We have been very lucky and have had no major outbreaks of disease. This year we did not lose one worm by disease but when spinning we had two which spun together and got tangled in each other's threads. The top part of the body was black and similar to the silkworm stage but the bottom half lived and one actually split the skin of the pupa half and although enclosed in the cocoon still, laid eggs. We had one cocoon in which three worms had spun and they all progressed to the moth stage and tried to emerge but the triple layer of silk was too much for them all. We released them on noticing that there was a typical brown stain of all cocoons but no hole where any moth had emerged.

The horny part which comprises the mouth falls off first. A split appears on the head and a new head comes through the split in the old one. The old skin drops off and the head works from side to side as the front part of its body is pulled through the opening. It rests for a while and begins again. By changing its positions with muscular contractions it draws itself forward, also dragging itself forward with its front 1egs. The worm remains fully stretched and motionless after finally casting its old skin allowing the new one, time to dry and harden. When a worm is moulting it is imperative that it is quiet and that the worm is not disturbed as the worm ii in a delicate state. The silkworm grows so quickly that it has to shed its skin four times in its short lifetime. The silkworm has become a light beige to white colour. It is made up of eight segments which have a small black head attached to the front end of the body and a final segment containing the anus. The Iast segment also contains a small hook'like structure which darkens just before the silkworm starts to.spin- Attached to the first segment are three pairs of jointed legs with a hook like grasping attachment on the base of each. These legs are surrounded by short hairs. The third, fourth, fifth and sixth segments all have a pair of legs attached to them. These legs are larger than the legs attached to the first,. head segment and have sucker like attachements on the base of the legs. They are also surrounded by short hairs which also run from the last segment to the segment containing the anus. This is similar to the telsun of Crustacea and contains a pair of sucker like attachments. On each segment of the body is a round black hole called a sphincter. There are nine pairs of these all down the length of the body. The spincal is the opening for the respiratory system and comects to a seties of tracheolei runrung through the body and carrying oxygen to all parts. It leads off the sphincter. The second segment of the body has four brown semicircles which protude from under skin. Also running down the body above the sphincters is a line of indentations. Thirty to forty days after it has hatched the silkworm begins to spin. For the last week of its life a silkworm eats more than for all the rest of its life. During this week several changes occur in the appearance of the silkworm. First the front segments of the body become transparent and this spreads down the body. The colour changes to a deeper beige purple colour and the skin looks tight. The silk glands are at this time preparing the silk and the body is changing in preparation for spinning the cocoon. The body thickens and the appetitie diminishes. The silkworm becomes restless and starts climbing the sides of the box and raising itself up on its hind legs and attempting to grasp on to objects.

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