Black widow spiders are now creeping farther north than ever.
A new study that uses observations from citizen scientists found that the notorious arachnids have expanded their northern range since the 1960s, pushing more and more toward Canada.
The change is probably related to climate changes in recent decades, and it is believed that temperatures during the hottest months of the year are an important driver of its activity.
Black widow spiders are now creeping farther north than ever. A new study that uses observations from citizen scientists found that the notorious arachnids have expanded their range since the 1960s
In the study published in the journal PlOS One, researchers at McGill University created an updated map of species distribution using contributions from citizen science to online databases and museum collections.
The team investigated two species of spiders: the northern black widow (Latrodectus variolus) and the black spider (Sphodros niger).
Using statistical tests and modeling tools, the researchers plotted a current range for the two species.
Then, they compared this with the historical data, revealing how the two have changed.
According to the team, spider webs seem to have expanded their range to the north, while their distribution in the southwestern United States has decreased.
Black widows also seem to be pushing toward states further north and Canada.
"Our models show the first reliable distribution maps of these two species," the researchers said.
"The next logical step is to make sampling efforts in typical habitats associated with these species in our predicted range to further validate the models.
"We propose to turn to citizen scientists by launching a monitoring project through a platform such as Bugguide and iNaturalist to produce a large-scale sampling effort.
"This would represent a fast, low-cost, highly efficient and innovative way to test these large-scale prediction models."
According to the team, spider webs seem to have expanded their range to the north, while their distribution in the southwestern United States has decreased. Black widows, also seem to be pushing towards the northern states and Canada, as shown in the map above
The researchers say that weather was an important factor in predicting the current range of spiders.
For bag-cloth spiders, the average temperature of the coldest three months was more important for where they could be found.
For black widows, on the other hand, the average temperature of the three warmest months was the most significant.
IS IT A SPIDER FEAR IN OUR DNA?
Recent research has claimed that fear of spiders is a survival feature written in our DNA.
The scholar suggests that, dating back hundreds of thousands of years, the instinct to avoid arachnids developed as an evolutionary response to a dangerous threat.
It could mean that arachnophobia, one of the most oppressive phobias, represents a finely tuned survival instinct.
And it could be traced back to early human evolution in Africa, where spiders with very strong venom existed millions of years ago.
Study leader Joshua New, of Columbia University in New York, said: "Several species of spiders with specific venoms of powerful vertebrates populated Africa much earlier than hominids and have coexisted there for tens of millions of years.
"Humans were at perennial, unpredictable and significant risk of finding highly poisonous spiders in their ancestral environments."
The researchers say that updated maps could help predict the changing range of rare species as the climate changes.
"Spider distributions are relatively little known, and range maps are often based just where scientists have found the species," Wang said.
"Using the black widow spider and the black spider as an example, this article illustrates that we can (and should) incorporate citizen science data and distribution modeling techniques to help close knowledge gaps in less studied species."