Texas Hospital Tries to Stop Birds Living in Nearby Trees, Accidentally Creates Haven for North America's Most Venomous Caterpillar

A Texas hospital's attempts to deter birds have accidentally created a haven for North American's most venomous caterpillar species, whose painful sting has been compared to breaking a bone.

Nets were put up on the oak trees that line the sidewalks of Texas Medical Center in Houston to stop birds like grackles and pigeons—which can carry diseases and create a mess—from gathering. But by putting the birds off from landing on the trees, the institution created a new problem. With no birds to eat them, the population of bugs commonly known as "asps" exploded.

After studying the area for three years, researchers found the caterpillars were 7,300 percent more abundant on netted trees compared to those without protection. The paper was published in the journal Biology Letters.

Also known as Megalopyge opercularis or puss moth caterpillars, the insects are the most poisonous caterpillars in North America. The creatures are covered in spines linked to a sac filled with poison. If someone brushes against an asp, the protrusions break off and stick into the skin, releasing venom.

After around five minutes, the victim will experience an intense throbbing pain, which then spreads. Stings can be accompanied by headaches, vomiting and nausea, as well as stomach pains. Red spots may appear on the skin, which can remain for up to five days.

Mattheau Comerford, an ecology and evolutionary biology graduate student at Rice University who researched the asp problem, commented in a statement: "I've been stung by a lot of things and an asp sting definitely ranks high up there."

Comerford explained: "It takes about 10 minutes before the pain kicks in so you might not even realize you've been stung at first. It feels like a broken bone and the pain lasts for hours. I was stung on the wrist and the pain traveled up my arm, into my armpit, and my jaw started to feel pain."

Some 10 million people visit the Texas Medical Center each year. The site employs more than 106,000 people.

"In this area, there is a high density of people with allergies and compromised or depleted immune systems, putting them at a higher risk for the ill effects of the asp stings," said Comerford.

asp, Megalopyge opercularis, caterpillar, Texas Medical Center, Rice University
Asps are covered in venomous spines that release poison when touched. Brandon Martin/Rice University

Glen Hood, who led the study at Rice University and is a research assistant professor of biological sciences at Wayne State University, said in a statement: "There are a lot of people that congregate in the green spaces of TMC [Texas Medical Center]. It becomes this scenario of what's worse—bird guano or venomous asps—and is there a happy medium?"

Hood commented: "It's highly suggestive that when you don't take into account the natural interactions taking place within a community or ecosystem, even in an urban setting, it can cause unforeseen consequences."

Scott Egan, an assistant professor of biosciences at Rice University who has dedicated almost two decades to researching live oaks, suggested organizations can find themselves in a tricky situation when it comes to controlling different animals.

"There is no 'bad guy' here," he said. "Urban bird pests are a real problem, and birds can carry diseases and pose health risks, too. Netting trees is a way to address that problem, and we do not know if netting trees leads to an increase in asp stings. What our study shows is the complexity of the problem. Asps are yet another dimension to something that was already a multi-dimensional problem."