Question

Which product of caterpillar forms silk?
(A) Skin
(B) Secretion
(C) Excretion
(D) Hair

Answer 1

Hint: As we know that silk is extracted from the cocoons of the silkworms, And cocoons are developed by the secretion of sericin by silkworms.Cocoons are made up of silk threads which are made by the silkworm to protect itself.

Complete step by step answer:
Larva stage-A female moth lays tiny eggs (300-500) and then the eggs (larvae) hatch out with silkworms
These silkworms feed on the leaves of the mulberry tree and after 30-40 days they start developing the cocoon

Cocoon formation-The saliva secreted by a silkworm is made up of a very fibre filament of fibroin protein from two glands on its head. The silk fibres are the hardened saliva of silkworm upon exposure to air.
Once the cocoon formation is complete, it stays in it for around 2 weeks.

Adult moth-The larvae change to pupa in the cocoon and after 2 weeks the pupa emerges out as an adult moth which looks for mates and then the cycle continues.

So, the correct answer is Option A .

Note: The silkworms inside the cocoon are killed by heating the cocoons, the heat does not damage the silk threads and helps in unraveling it.A thread from a mulberry cocoon can be around 900 meters long.Silkworms only feed on mulberry leaves.For making 1 kg of silk, we need over 50,000 cocoons .Some wild silkworms secrete yellow silk threads, to camouflage in the dried leaves but in many years of breeding whiter silk threads are obtained which can be dyed easily without the need for bleaching.