The tarantula, later named Parker, was identified as a Mexican red rump. It is about four months old and relatively harmless.
The ISPCA welcomed the unusual guest to their Donegal Animal Rehabilitation Centre (ARC) following an urgent call for help from the surprised shopper.
Once the tarantula has fully matured to adulthood, it can be determined whether it is male or female.
ISPCA centre manager Denise McCausland said: “Parker was carefully captured and transferred in a secure box before being admitted to the ISPCA ARC for a closer inspection.
"A veterinary examination confirmed that Parker was very dehydrated and lethargic after his travels but after some water and mini crickets to eat, he began to perk up very quickly.
“Parker was placed in an appropriate humid habitat in temperature and moisture levels suitable for his species and was closely monitored over a number of weeks.
"He has already grown in size and is continuously spinning elaborate webs all around his enclosure. Parker is thriving well; his previous fuzz of hair is thickening well as he grows, also molting in recent days."
The good news is the tarantula is going to stay in Co Donegal, at Alcorns’ Tropical World in Letterkenny.
McCausland added: “This is a vulnerable time for Tarantulas as his new exoskeleton has to harden in the coming days and weeks so we are being extra careful.
"Parker will be transferred to Alcorn’s Tropical World nearby where his permanent home awaits.
"There Parker can live the solitary life he requires in a purpose built vivarium fit for a spider Prince or Princess”.
The ISPCA recommends anyone thinking of getting an exotic pet should consider whether they can commit to providing care throughout the animal’s entire life.
Some species can live for 30 or even 50 years and many other factors need to be considered such as correct lighting, heating, humidity, diet and other needs.
As with all animals, exotic pets have five basic animal welfare needs and owners have a legal duty to ensure they are a responsible pet owner.