Northern black widow spiders have never before been found in Canada. But they are expanding their range. Scientists think this is due to climate change. The small spider with the very painful bite likes warm weather. Northern black widows have now been found 58 miles (94 km) farther north than they were in 1990. Ordinary people are helping researchers track the spiders. They capture pictures with their smart phones and post them on citizen science apps. It’s important to know the spider’s range. This allows local medical providers to be prepared to treat bites.