I own a copy of the Peterson Field Guide Field Guide to Moths of Northeastern North America and I’ve found that it’s pretty helpful for moths in my area.
I also have Ron Russo’s recently published Plant Galls of the Western United States, which despite being focused on galls nowhere near where I live, still is a very fascinating book with beautiful pictures and informative text on galls in general. I bought it mostly to help me fill out the Gallformers.org database, but also to bring it with me whenever I visit California to see my family.
Beetles of Eastern North America by Arthur V. Evans is a real banger. Big book for less than $30. Totally recommend it for anyone in, well, eastern North America.
I don’t use any ID books - I just make everything up!
I use an old copy of Borror and Delong’s Introduction to the Study of Insects. I should probably get a new copy, but it is not cheap. A good all around resource, though.
Merrit and Cummins Introduction to the Aquatic Insects of North America is pretty good for that group. Again, my copy is old.
I use a few other books, but most are old and specific to Canada.
I identify moths (Noctuids, mainly) and use Moth Photographer’s Group website to come up with an initial identification, then use Bugguide, and other sites to confirm the identification. MPG has links to various resources for each species - very helpful.
한국 매미 생태도감 (The Encyclopedia of Korean Cicadas); 김선주 & 송재형, 2017 … (Though, honestly, just the top-view species comparison) http://www.econature.co.kr/ecobook/143227
산림 말벌 바로 알기 (Social Wasps of the Forest); 대한민국 산림청 (Korea Forest Service), 2019 … PDF online here
One that I’d like to pick up in the future is:
한국 육서 노린재 (The Terrestrial Heteroptera of Korea); 안수정, 김원근*, 김상수, 박정규, 2018 (* 김원근 is @wongun on iNaturalist) http://www.econature.co.kr/144237
Book of India Butterflies (Isaac Kehimkar) (2008 edition ) there is a new improved edition available
Butterflies of Uttarakhand - A field Guide (Sanjay Sondhi & K Kunte)
Three Photo Pamphlets on Moths (Moths of Pawalgarh, Moths of Devalsari, & Moths of Gori Valley)
Butterflies of Garo Hills (Sanjay Sondhi & K Kunte, et al)
Butterflies and Moths of Pakke Tiger Reserve (Sanjay Sondhi & K Kunte)
Encyclopedia of Indian Natural History
***e Books
7. Dragonflies and Damselflies of Peninsular India-A Field Guide. K.A.Subramanian (2005) E-Book of Project Lifescape. Centre for Ecological Sciences,
8. Fauna of British India, including Ceylon and Burma in many volumes (PDF / ebook)
Knowing that you also identify African butterflies ( particularly skippers ) I wondered if you are aware of, “Butterflies and Skippers of the Afrotropical Region” , by Marc C. Williams?
I don’t know if it will ever actually be printed, but at the moment it’s available as a free internet resource. All of the known species are listed with their known localities, and over two thousand species have accompanying photographs. It’s still a work in progress and if you don’t know the Genus you’re looking for, it can be quite frustrating as you can’t just page through looking for a matching picture, but It’s become my favorite resource for identifying African butterflies.
I am aware of that resource (as well as AfroMoths) since I’ve used it to ID some African lepidoptera on iNat before. It’s definitely a comprehensive site. Online field guides like those are very helpful, yet for niche groups they can be unfortunately hard to come by.
On most of my Butterfly IDs, I cite Riley 1975. That would be A Field Guide to the Butterflies of the West Indies, by Norman D. Riley, published by Collins.
I have not found any guides to the other insect groups of this region.
The main series for British (and Irish, and fairly useful for neighbouring Europe) insects is the Royal Entomological Society’s Handbooks. The out of print ones can be downloaded free, but keep in mind they may also be out of date. https://www.royensoc.co.uk/out-print-handbooks
I have Ron Russo’s plant galls book, which is somewhat handy. I really wish there was a corresponding book for my area (Texas).
The Peterson Eastern NA book is very useful.