Great essay Aria!! There's only a couple minor grammatical errors that I'm seeing. Everything else looks fantastic!
"..., which takes around 72-94 days,
This comma needs to be there because "which takes around 72-94 days" is an appositive. An appositive is something that elaborates on the subject of the sentence, and the sentence usually makes perfect sense without the appositive. When appositives are inserted, to make it clear to the reader, I was taught that they are usually opened and closed with a comma, but I don't know if that is an official rule.
"... in which the silk
The "s" is added onto "textile" here because of subject-verb agreement. "Are" is a plural verb, so the subject of the sentence must also be plural, because the verb and subject must align.
"After 10 days,
In this case, "that" is an unnecessary word. The comma is added after "days" because "After 10 days" is an introductory clause. The rest of the sentence can be read without the introductory clause and still make sense, just as a sentence can be read without appositives as well.
"... start to
"Secret" and "secrete" actually mean different things. However, the main difference is that "secret" can be a noun or an adjective, while "secrete" is a verb. Because of this word's position function in this particular sentence, it needs to be a verb, so "secrete" needs to be used.
"... known as a
In this case, "a" needs to be added because there are many cocoons, and in this case, the sentence is referring to just one cocoon. The word "a" makes it so that the sentence is referring to one cocoon out of many cocoons.
"In the next 3-8 days,
The comma needs to because it is an introductory phrase, which I explained a couple paragraphs above this one.
"At the end of this period,
Same thing again... it's an introductory clause so it should have a comma after it.
"of the silk,
that their length varied with lengths varying
between 300-900 meters,
The commas needs to be added because the information between them isn't necessary for the sentence to make sense; it's another appositive. Changing "that their length varied" to "with lengths varying" is something that I can't remember a rule that applies, but I know that "with lengths varying" works a little bit better in that sentence than "that their length varied". I'll do some research and post again if I can find a rule to verify my correction.
..." This is one of those tricky things... In this case, because the dyeing isn't happening at the present (in the essay) then it needs to be "dyed" because it's referring to the dyeing occurring at a different time in the future. I can't explain it very well, but "will be dyed" is what is called future perfect tense. You can Google search "future perfect tense" and hopefully you can find a website that can explain it better than I can.
Great job on this essay, Aria! Just watch those introductory clauses and appositives... you're doing great! Keep it up!