A lethal heat wave is plaguing parts of Europe, and it's so intense that meteorologists are calling it "Lucifer." The heat wave is fuelling wildfires, shutting down tourist attractions, and being blamed for causing heart attacks. But as if that isn't enough, Romanians also have to worry about Lucifer fueling wasp and bee attacks.

According to local Romanian news sources, seven people swimming in a river were rushed to the hospital this week after being attacked by what eyewitnesses claim were wasps. Three victims reportedly went into anaphylactic shock, and one of them later died.

Local sources claim that dozens of other attacks have taken place over the past couple of weeks, including a severe attack on a 19-year-old.

"Climate change is going to really bring out some honey bee and social wasp populations in a big way," Lynn Kimsey, a professor of entomology at the University of California, Davis, told me in a phone call. "They're going to be more active, and probably more aggressive, because it's hot."

While she said that warmer weather is conducive to attacks from both honey bees and wasps, it's unclear as to whether honey bees or wasps are the actual culprits in Romania.

Local coverage relies on eyewitness accounts that don't provide a description of the insects, and Kimsey pointed out that people commonly can't distinguish honey bees from wasps. It doesn't help that media depicted both wasps and bees in its coverage.

However, there are some hints as to which species could be behind the attacks, and all of them are provoked by heat events like what Romania is experiencing now.

There are several species of wasp that are both native and invasive to Romania, including the black and yellow mud dauber, the chestnut gall wasp, the paper wasp, and the oriental hornet. But of these, Kimsey said the paper wasp and oriental hornet are the only ones to really worry about.

Oriental hornets are notorious for attacking humans. Their colony peaks at this time of year, and Kimsey believes that climate change could be driving a rise in their population.

Oriental hornets are a seasonal species—meaning the colony dies off in the winter, and the surviving queen bees start new colonies the following spring. So more queen bees making it through the winter means you can expect more colonies.

"I do think that the rising temperatures that we're seeing around the globe are probably enhancing these [hornet] populations because you get more [queen bee] survivorship," she said. "The cold temperatures seem to kill off more queens, but that's speculation on my part because we don't really have hard evidence."

While most people think of think of extreme weather events like hurricanes and floods as an immediate risk of climate change, we could see more bee and wasp attacks, too