Experts say False Black Widow Spiders are now more prevalent in Sligo than most other counties.
A three-year-old boy in Sligo got bitten by the spider while walking through a field with his father.
While a Waterford woman spent 6 days in hospital recovering.
The spider was first recorded in Ireland in the 1990's and has since spread around much of the nation with experts saying climate change is having an impact on their larger numbers.
Dr Michel Dugon of NUI Galway, says the spider are now prevalent in several counties including Sligo.
If bitten the advice is to wash the area with soap and water, apply a cold press or ice to reduce swelling, raise or elevate the affected area if possible, and try and avoid scratching the area to reduce the risk of infection.
While not fatal, the sting can be very painful and can get infected.
But, Dr Dugon says the worst course of action is to try and fumigate the, which won't work.
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