The Ningpo Syllabary（宁波方言音节），P28

The first evidence is from 字學指南（明萬曆刊本）卷1 folio 45b, under the section 異體同音同義/三字仝. Based on the fanqie 敵德, here ⿱牧虫 is likely misinterpretation of the cursive form of 𧎬, a variant of both 𧎢 and 蟘.



▲ zi.tools: cursive script examples of 特

Here is the complete page of the second evidence:


▲ 重訂直音篇（練川明德書院明萬曆34年刊本）卷6 folio 96b

Here ⿱牧虫 is in the last section of the 虫部337, as mentioned in the preface:「今於諸篇韻等搜集四萬三千餘字成篇……元篇有音無註者三千餘字今亦收之」.

In this section, all characters(𧋟𧈧𧊭𧊽蚫⿱隴虫⿱牧虫𧊪𧈦⿱⿰虫口口𧓁𧕸𧏫蟦⿰虫⿱雨灬⿰虫叔(WS2021-03553)䗮⿰虫⿳龷冖虫𧈹⿰虫任⿱猒虫𧒼), except ⿱牧虫, can be found in 四聲篇海, which implies that 直音篇 is heavily influenced by 四聲篇海. However, 四聲篇海 includes a character very similar to ⿱牧虫


▲大明成化丁亥重刊改併五音類聚四聲篇卷13 folio 5b. 虫部/6畫, quotes 龍龕. （⿱⿲⿱𠃊一丨又虫，音𢪛）


▲ 大明萬曆乙亥重刊改併五音類聚四聲篇卷13 folio 5b（⿱⿲⿱𠃊一丨又虫，音𭣣）

Here is a 龍龕 evidence:


▲ 龍龕手鑑（江安傅氏雙鑑樓藏宋刊本）卷2 folio 9a（虫部，平聲）

Although ⿲⿱𠃊一丨又 can be considered as an intermediate form between 牧 and 收. The fact that this character is placed in 平聲 rules out that it is ⿱牧虫. It might well be ⿱收虫, or even misprint of an encoded character, such as 𧉭 (since 龍龕 does not include this character anyway).

The third evidence provided in #3045 is a syllable compiled by Paul Georg Von Mollendorff in 1901. It is not intended to be a dictionary containing rare characters, the ⿱牧虫 here is likely a misprint of 蝥.

In all, current evidences are somehow questionable. But since we have three of them, I suggest to encode it as-is.