Explain the riddle in Harry Potter

Think about why people always wear masks. Spiders always disguise themselves according to their environment.

Spiders are always where you don't notice them.

Tell me what can always be fixed. Spiders can weave webs.

Middle, middle, tail, tail? Spiders weave webs through glands on their tails.

Finally, tell me when I can't think of a word.

That word is often mentioned. The word spider in spider is homophonic with pig.

Connect them, answer me,

What is the last animal you want to kiss? Then this animal is a spider.