Written and drawn by mangaka Okayado (Inui Takemaru), this chapter was released in Japan on December 19th, 2016, by the Japanese publishing company Tokuma Shoten within the seinen manga and anime magazine, Monthly Comic Ryū.
The unnamed mosquito-girl in Chapter 49 is dressed like Shimakaze from Kantai Collection.
There is a notable difference between the magazine and the tankobon versions; in the magazine, the unnamed mosquito-girl was originally shown to have only two arms, which contradicted her later appearances which showed her having four. This was eventually corrected with the tankobon release, where the mosquito-girl is consistently depicted with four arms.
Okayado states that their first appearance in chapter 49 and chapter 50 were very incomplete, and as an apology, he asked fans to choose to be one of the 20 male background characters that appeared in the chapter (that's why they all had numbers). He added them in the final release of the volume, along with fixes on the girls: a more gyaru mosquito + two more arms; a more shiny leech + some sort of eye emojis on her face; more makeup for the lamprey girl.
While the original call was for twenty human male "Mob Characters", Okayado tried to fit as many entry characters as possible into the chapter. As a result many crowd and location scenes in the chapter were altered from their appearance in the original magazine release to include these characters.
The appearance of the Mothman girls were also drastically altered (with their wings moving from being attached to their backs to being attached to their heads, their arms increasing in number, their fur being relocated to their biceps and their entire wardrobe being altered). This was possible done to match their design in the Species Bestiary Card of OAD 2: Everyday Life when Rachnera Disappears, which was released in the same year as the manga volume that this chapter was collected in.