If you are thinking about a secondary world, it's important to look at vermin because they have an astonishingly big influence on the culture of a world. I just recently read an article about how mosquitoes don't like chickens, with the implication that people should consider sleeping with chickens beside their beds - an unusual cultural practice to be sure, but one that might become common if it proves unusually effective.
Plagues have changed history, and vermin are often disease vectors. We also see foods that are forbidden or must be cooked in particular ways due to the possibility of parasitic infections. These things drive and alter societal development.
We spoke about Kameron Hurley's Gods' War series, where bugs are used as a power source, and people have to avoid house-sized insects, or sometimes use bugs for rejuvenation. This is an imaginative and thorough use of bugs in a sf/f scenario.
We can also talk about how vermin and parasites inspire changes of clothing, such as use of shoes and boots to go into water. We spoke about the guinea worm, which because of the efforts of President Jimmy Carter and his educational organization, is about to be eradicated (the first parasitic infection ever).
People often spice their food to discourage bacteria and pests. Bugs can show up as eggs in flour or cereals and hatch if they are left too long. Sailors had to deal with weevils in their hard tack, and of course flies lay eggs in fresher food. We were united in our horror of maggots!
Now, of course, there are also insects and other unwanted creatures that can be used as a food source. Generally speaking, if you want to eat mealworms or crickets or even snails, you should feed them things that taste good. This is also true with meat animals like cows (or bears, in Prince Caspian).
More gross things: tsetse flies, bedbugs, bot flies...
Che noted that humans create good environments for vermin to thrive.
Are pigeons vermin? Some people consider them so, but they also have the fastest level flying speed of any bird and can give milk out of their throats!
Another thing that can arise from the presence of vermin is a symbiotic relationship, as when birds live with hippos or crocodiles and rid them of pests.
Vultures can be considered vermin. I highly recommend the National Geographic article about them. Scavengers are really important to keep disease from spreading, however. Their role is vital. Tasmanian devils keep the roads clear of roadkill in Tasmania (and have amazing jaw muscles!).
Morgan asked if, when humans move to a world, they might bring scavengers to deal with the stuff they have that needs to be cleaned up.
More pests: fruit flies, Mediterranean fruit flies, termites, wasps, fire ants, ticks...
Che noted that by fighting our vermin, we also cause them to evolve. She also said that wasps and ants are related.
Possums will eat ticks in your yard, so even if they seem like vermin, don't discourage them!
Raccoons are cute but fearless and capable of serious bites and scratches. They also carry a dangerous parasite in their feces. Skunks stink, which is why they are often driven out even though they don't cause much other trouble.
Kimberly told us that bees and wasps hate noisy places so she blasted Metallica at them for 12 hours (more than one occasion) and they left.
We did touch briefly on the question of humans as vermin, but agreed that when people try to do that in SF they usually only have humans called vermin as an insult, and don't usually have humans taking on the role of a vermin species. What might that look like?
Thanks to everyone who attended. I'm about to run off to another hangout!