Inspired by pre-trash-day clear-out of back of fridge...
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Most galactic species call the Terrans 'Death Worlders', for the myriad ways their home planet will kill you.
A few, wiser, call that planet a 'Life World' {Spit_!!}, and shun Sol System as if about to go 'nova'.
Consider how Terrans' mites, ants and roaches seem immune to most shipping quarantine procedures. 'Official' carriers know their business, but it reflects in their cost. 'Casual' carriers, some no better than smugglers, are less wary. Buyer beware: Too often, 'clearing' such cargo significantly degrades its value. And if those little monsters get through 'Dock Control' to your station or back-country base ? Beyond possible punitive penalties, they put the 'Ay-ay-ay !!' into 'Invasive Species'. Four planets have been accidentally 'terraformed' thus, while at least three eights pay heavily for Terran 'Pest Control' services.
Before the Ixarthian Supremacy's infamous over-reach and fall, they'd lost several colonies to 'Shrooms'. Those hapless insectoids found their air-sacks beset by a Terran 'fungus'. Neither plant, animal nor archaic bacteria, but branched from near their earliest 'common ancestor', this horror's air-borne 'spores' found such air-sacks most congenial, briskly spread hyphae within. Fortunate victims soon died of 'shock'. Many had hyphae invade their neural nets: Madness often ensued. The unlucky majority found 'Shrooms' erupting from their spiracles, spreading 'spores' near and far. Worse, these 'Shrooms' literally 'made a meal' of Ixarthian crops and crop-based construction materials. So, almost anything less than 'hull metal'.
Of course, the Ixarthians repeatedly complained to Terran authorities. Who shrugged, replied that if the Ixarthians had dealt with their free-booting 'Corsairs' and 'Pirates' rather than covertly encouraging those raids and pillage from which infestation had spread...
To add insult to injury, Terran mites, ants and roaches were also introduced via such pillage. And they thrived on 'Shrooms'. As one Ixarthian investigator reported, before blasting her-self, 'Shrooms' in your air-sacks were bad enough, but having a multitude of mites iggling, wriggling and nibbling within, too...
It is unclear how Ixarthian pirates avoided a still-worse fate. Such raids could have introdued 'MICE' or 'RATS'. These near-ubiquitous, nigh-omnivorous midi-vermin can apparently thrive on a diet of ants and roaches. They are the reason most Terran ships and colonies have at least one 'CAT'. Yes, those terrifying / endearing 'Fang-Claws', with whom unwary Galactics are cautioned to 'Make Nice-- Or Else'. The Terran joke goes that, back in prehistory, Cats domesticated humans to at-need providers, just as humans had domesticated predatory wolves to dogs. Laugh politely: 'Commensal' is a two-way street...
There are confirmed reports of multi-species' Pirate attacks hastily abandoned when their target's irate Ship's Cat or Cats went 'Full Momma' on boarders. Beyond much 'soft tissue' damage, 'Friendly Fire' casualties were routine. No surprise given a Cat's hyper-nimble athleticism and most pirates' poor 'Fire Disipline'. Worse, a Cat's erect fur can stand-off several grazing pulse-gun bolts. The resulting stench is almost a weapon in its own right. Any hit short of hard-kill usually made the Cat angrier. Oh, and usually inspired crew to scream with fury, wield improvised but effective weapons, swarm and stomp boarders...
Further, by all that you hold dear, do *NOT* let Terran Pigs, Goats, Rabbits or Snakes loose in your eco-system. Short of nuking the entire land-mass from orbit, they'll survive, thrive. As will the mites, ants, roaches and umpteen fungus varieties' spores they surely brought along...
Life World
Re: Life World
See Terry Pratchett's Real Cats for what a shipboard moggy is probably like.