Invert related ones that are coming up: Arachtober (all October) Nudivember (all November) 12DaysOfCrustmas or Crustmas (December, usually)
How the Grunch stole Crustmas
Which is Crustmas time lol
I'm also more than happy to add specialty invertebrate hashtags, like #Arachtober#Crustmas, so please feel free to let me know about them!