There are new details on the spiders discovered at the Port of Guam. What was initially thought to be black widow spiders has now been confirmed as brown widows. Today, entomologists showed us the species up close, and explained what people should know about them.

At the University of Guam, insect experts are taking a closer look at the spiders that caused quite a stir. Biosecurity chief and state entomologist Christopher Rosario says the spiders were found inside a port warehouse where cargo is routinely inspected.

"We were pulling out adults, newly hatched spiders and we got over a dozen eggs, which indicates that we have different overlapping generations of spiders in this secluded area," he explained. "But there have been reports from other people that said they’ve seen them in the past."

They were first suspected to be an established population of black widows due to their hourglass symbol. UOG assistant entomologist Dr. Daniel Johnson said, "Sometimes, we have color morphs of black widow spiders that can be very pale white, to dark brown to pale to even dark black."

But after careful examination, Dr. Johnson confirmed they are actually brown widow spiders, thanks to a distinctive trait that helps differentiate them from their more famous relative. "This is the only widow spider that can make actual spikes on the outer surface of the egg sacs," he said.

Still, Johnson warns these are highly invasive species whose venom can cause intolerable pain, especially in vulnerable populations, as he said, "The venom nature of the black widow is significantly more potent and toxic than the brown widow. But still, we can’t ignore the toxic nature of the brown widow because it is also a neurotoxic venom that can cause some damage to babies, kids and infants."

"You will immediately throw up and will sweat a lot. It is painful. It’s not tolerable."

But while brown widows are venomous, Johnson says they are generally shy and bites are rare. "They are not going to come after us and inject venoms into our bodies. Only if we handle them roughly or if we trigger them to bite us, then maybe at that point they will deliver a painful and dangerous bite," he shared.

Rosario says because Guam is a major shipping hub, insects and other invasive species can sometimes arrive by hitchhiking in cargo. "I’ve gone to people’s houses and opened up the hoods of their cars and have seen black widows and have collected eggs, too," he said.

When asked about community reports of black widow sightings on Guam outside the Port, Rosario says their presence here is possible, but he can’t say for sure without actual specimens. He added, "The community are our eyes and ears. So I highly encourage them to call the pest hotline if they think they have a black widow or brown widow, call the pest hotline."

In the meantime, he says the area at the Port has already been treated, and follow-up inspections did not find any additional spiders. The state epidemiologist has been alerted about the presence of brown widow spiders on guam. A physicians alert is expected to be forthcoming.

But if you do get bit by any widow, Dr. Johnson warned to "immediately seek medical service".