I have no preference how the copyright is listed, but since this is a derivative work, I think it would be legal for me to be listed as the sole copyright owner, in much the same way that a field guide containing many licensed photos does not list all of those photographers as the copyright holders of the field guide. The CC BY-NC license implicitly grants the permission to make derivatives, and I have attributed all the photographers whose works I used, so I didn't violate the attribution clause of the CC BY-NC license. One part of the license that I guess I did not abide by is to note that modifications were made, which I'll do now.

For the unlicensed images, I obtained permission to use them via direct communication. If any of the copyright holders have changed their mind, they can let me know and I'll take this down, or modify it to use a different image.

If I'm missing something and this work somehow violates BugGuides policies, I will take it down. Again, please just let me know.

This response is rife with legal misinformation and shows a concerningly poor understanding of copyright and licensing. Some of these are very basic points of the licensing code that you frankly have no business missing. You should always read and understand the legal code for a copyright license in its entirety before using it.

Being a derivative work does not permit you to ignore the requirements of the CC BY-NC license. Any re-use requires meeting the attribution requirements noted above as these are the terms of the license. It permits you to create a derivative work without paying royalties to the copyright holder for a license. Failure to include all material required in the license (including stating that it's under the CC BY-NC license) makes it unlicensed use, unless separate licensing terms were expressly given by the copyright holder. Also under the code, you would then no longer have the right to use the work.

You are not, legally, the sole copyright holder and may not claim to be. Your copyright is limited to the arrangement and any original text not created by another author (and only to the extent that such additions are even copyrightable). It does not extend to those portions originally created by another author. This is plainly stated by the US Copyright Office. Should you directly and intentionally claim sole copyright on such an upload as you've suggested, the image will be removed, and the question of suspension will be raised with staff as that's a form of theft.

You'll generally only see unscrupulous field guides omit photo credit, so I would not use those as an example. If they care about not being sued by copyright holders, they have all of the boxes checked on the publisher's end and have actually followed any and all licensing requirements. Both the author and publisher can be held liable for lapses in their use of copyrighted material, and it becomes expensive really quickly.

If images are used with permission, they aren't unlicensed. That actually is the license to use it. Again, that license may have terms that need to be included, especially if the licensing differs from your own default licensing. So as your default is listed as CC BY-ND-NC 1.0, you need to specify those that are "all rights reserved" and "used with permission". Not including that information would erroneously suggest that people other than yourself can re-use the material under CC BY-ND-NC 1.0 when this isn't the case for most of these images.

Insofar as BugGuide policy, part of the issue is about preventing liability to the site. This means uploaders need to give proper documentation and not falsify claims of copyright. There are legal issues with knowingly hosting material that doesn't comply with copyright. Site editors are generally more proactive, and images that have an erroneous statement in the copyright field (as originally here) that would re-license the material or that expressly violate a license (as originally here on several points) may be removed on the spot. There's a reason the copyright field is editable.

Glad others are finding it useful. I've actually used it a number of times myself. I feel like there's a lot of great info like this "hidden" in the comments by experts on BG

I'm hoping they become more visible so all can use them. Martin Hauser has done several on syrphids, placed on genus Info pages in most cases. More wing views like these would be an excellent addition for bee flies.