So I have a bug race in my universe and I wanted to add them into a part of my story. But I was curious on how a bug would fly through space. My original thought is since they evolved off of a planet then they would flap their wings through space even though it doesn't do anything to help them fly. But I still don't know how they would actually fly through space. Any thoughts.
You want to look at propulsion in space. You might take the lightning bug approach and have your bugs use an ion drive or something. Another option is like a lot of bugs that drift on the wind, they could sail on solar wind currents. This one looks interesting and includes a quick summary of action reaction in a vacuum: NASA says puzzling new space drive can generate thrust without propellant
Interestingly my main story involves tiny robots that travel through space using a gravity lens. It is science fiction after all so if a concept cannot be disproven then it is good. Gravity is everywhere, we think of space as having zero gravity but in reality it just approaches a nearly perfect balance of push and pull in all directions, so if you can focus or redirect a portion of it then presto you have acceleration. Your wings might be just such a mechanism.
A couple of Star Trek references: Species 8472 (Voyager) has created biological spacecraft - purely for propulsion, since they themselves can survive within the vacuum of space (they've probably got some means of venting the vacuum into balance chambers within their bodies to equalise the pressure, in much the same way that SCUBA divers equalise pressure by breathing air at the same pressure as the surrounding fluid. Since insects [as I understand it] breathe by absorbing oxygen directly into their bodies, the equalisation isn't a problem, although breathing in the vacuum of space might be.) Captain Sisko (Deep Space Nine) builds a replica of an ancient Bajoran spacecraft that flew using the solar wind as its propellant (a technology that I believe NASA is now looking at seriously). They did, however, handwave how they got the spacecraft out of the atmosphere against the planet's gravity.
How does the lens work for propulsion? I've seen write-ups on using the lens to focus other propulsion systems, like beam propulsion, but not just a lens as a propulsion mechanism itself. I think the idea of some kind of lens apparatus in the wings, if it is workable, is pretty cool. The only question would be whether it makes sense for a species that evolved in atmosphere. That's something worth considering.
The wings could have a coating of exotic matter which, when moved, distorts the fabric of space, just enough to achieve propulsion.
I think it is best not to try to explain a sci-fi concept too much since the more write about the more problems/issues that could be exposed. For the bugs in space concept I would use more of a gravity shield concept, as far as we know nothing blocks gravity but that is only as much as we know now. For my own personal story I am thinking more along the lines of a magnifying glass that can distorts or focuses gravity much like ToeKneeBlack has suggested. For the OPs bugs evolving the ability one possibility would be deliberate genetic engineering. For example lets say we put people on the moon but can't grow food easily there, we modify a bug to be edible protein and give it the desire and ability to fly in space only to be attracted to the nearby moon for a rest/food/air stop, we trap them and voila home delivery service for meat. A stretch yes.
