Oh, I remember reading about Ishu Aigan! I haven't played it yet since bugs aren't really my thing, but here's some relevant stuff:
Perveloper's Captivity. A dark platformer/side-scrolling shooter with insects and dogs. Fair warning: heavy non-con.
Vrelnir's Degrees of Lewdity. Toggle on the insect, swarm, and monster kinks in the settings menu, After that, there are all manner of slugs, bugs, and creatures to be found in the deep forest and certain hidden locations...
Ark Thompson/Blue Axolotl's games (The Hunter, The Hunter 2, etc.). Tried some of them. The zombie stuff was too squicky for me, but if you can put up with that and a bit of grinding, they're pretty solid lewd RPGs focused on some of the themes ya asked for. (The other extreme kinks can be disabled in the menu, except for the zombie one which happens regardless of whether it's disabled, so fair warning.)
Anaximanes' Slugs and Bugs series. Haven't played 'em, but they're supposed to be good.
ParasiteInfection's Parasite Infection. Now seemingly abandoned, and the last update it received broke a lot of stuff. Worth playing if you can track down one of the older, more stable builds. This one was by an amateur western dev, but there are a bunch of Japanese games with a similar premise, where the player controls an alien parasite (check here on LC, 95, or the tfgames site). Another western game that's kind of reminiscent would be Invasive Species, but its themes are a bit different and less relevant.
Meandraco's Teraurge. It's been in development forever and will likely never get finished, but has great hard xenophilic content. Some of the aliens are kinda insect-like.
For cozier stuff, some of the big furry text-based rpgs feature humanoid bug girls:
Fenoxo's Corruption of the Champions (bee girls, ant girls, spider girls)
Fenoxo's Trials and Tainted Space (there's a whole bug planet with ant girls and spider girls, as well as a space station for breeding cute slug girls)
Innoxia's Lilith's Throne (spider girls)
Wahn's Flexible Survival (bee girls, ant girls, plus various roving non-humanoid bug monsters).
Another option would be Nranch's Rogschard, which has some more... unusual bug girls (the first girl in the game is a
drainfly).
Hope this helps :3
