子母虱 Lice Young And Old
假春嬌在傍，著意看著那妖王身上衣服，層層皆有虼蚤跳，件件皆排大臭蟲；子母虱密密濃濃，就如螻蟻出窩中。不覺的揭到第三層見肉之處，那金鈴上紛紛垓垓的，也不勝其數。假春娇在傍，着意看着那妖王身上衣服，层层皆有虼蚤跳，件件皆排大臭虫；子母虱密密浓浓，就如蝼蚁出窝中。不觉的揭到第三层见肉之处，那金铃上纷纷垓垓的，也不胜其数。
逐句解 Line by line
The false Chunjiao stood at his side, watching the clothes on the fiend king's body with fixed attention,
Two readings of one character in three characters. 著 in 著意 is zhuó, the lexical apply — to fix one's attention on something; the second 著, in 看著, is zhe, the light word that keeps the watching going. 傍 is páng, beside — the noun, not the verb for leaning on something.
layer upon layer of them alive with hopping fleas, garment after garment lined with fat bedbugs;
The prose stops being prose here without admitting it. Seven characters against seven, each opening on a doubled word and then 皆, all — the shape of a verse line. 排 is to be drawn up in rows, a word for troops.
lice young and old, thick and swarming, like mole crickets and ants pouring out of the nest.
子 is zǐ here, a full noun — young, offspring — and not the light ending it takes in 虱子 a few lines on. 螻蟻 pairs the mole cricket with the ant, a stock image for creatures too numerous and too small to matter.
Without noticing, he had lifted as far as the third layer, where the skin showed,
The fiend is the one doing the lifting, and 不覺的 says he is not thinking about it. 覺 is jué, to be aware, not the reading for sleep.
and on the golden bells there they were, teeming past all counting.
勝 is shēng, to be equal to a thing. 康熙 力部十畫 files 任也, 舉也 and 堪也 at 識蒸切, 音升 and keeps victory in a band of its own; the Ming 洪武正韻 puts 勝，任也、舉也、堪也 in the level tone beside 升 and 昇, cross-referencing 又敬韻 for the other sense; and 中原音韻, which records northern speech of the period, lists the character twice, once in 庚青 level with 聲 升 昇 and once in 庚青 departing with 聖 剩 盛. Modern speech has merged the two readings; none of these three had. And because 勝 now carries a level tone, the 不 in front of it stays bù instead of dropping. 垓垓 is a doubled word for swarming in vast numbers.
The vermin have done their job and the description is where the fun is. Layer by layer, the false maid works down through the monster king's clothes, and each layer is worse than the last: fleas, then bedbugs, then lice with their young. The prose is enjoying itself.
It is also, quietly, not prose. 層層皆有虼蚤跳，件件皆排大臭蟲；子母虱密密濃濃，就如螻蟻出窩中 is four lines of seven characters, and the two line-ends chime: 蟲 chóng and 中 zhōng. The source gives it no marker and no indent, so this edition keeps it as prose, which is the right call and also a small loss — the storyteller has slipped into verse to describe a man's underwear and nobody is meant to notice.
The last line is the one that matters to the plot. Working down to bare skin, he reaches the golden bells at the fiend's waist, and they are crawling too. The vermin were never about discomfort. They were about getting the man to take his belt off and then getting a reason to touch what is under it.