Bug (invertebrate)
"Bug" was a colloquial term for a primarily terrestrial invertebrate, specifically arthropods, but was also casually used to generically refer to any other form of insect or arachnid.

In 2151, while crew from the  sat around a campfire on the planet Archer IV, Travis Mayweather told a ghost story. Crewman Cutler noticed that previously nearby fireflies had gone, to which Commander  joked that Mayweather scared off the bugs. Afterward inside a tent, a bug found its way inside Tucker's sleeping bag. He requested Mayweather's boot to squash it before then requesting a phase-pistol to stun it instead. Tucker described the bug to T'Pol as an eight inch scorpion thing. ()

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Animals