Wizzie Brown, a program specialist with Texas A&M AgriLife Extension Service and our go-to insect expert, tackles this question from a Texas Standard listener:
Q: I got bit by a small insect on New Year’s, and I smushed it before I got a good look at it. But it left a blackish stain on my fingers when I did that. It was a little smelly, and it didn’t come off easily.
It’s difficult to identify the insect without a photo – not to mention the fact that it had already been smushed – Brown said, but based on the description she thinks it’s probably a stink bug.
“So, stink bug: It’s a true bug, and it stinks. But stink bugs are actually really cool insects because they have these glands in their thorax that are filled with chemicals that they can actually release on to the outside of their exoskeleton,” she said. “And the area that they release it to on the outside of their exoskeleton is actually designed in a special way that allows the chemicals to evaporate really quickly. That way, those chemicals get into the air and it causes that stinky smell.”
The smell is a defensive mechanism to ward off anything that may be trying to eat the stink bug, Brown said – but it’s is not the only insect to release a scent or a chemical that causes staining.
“I actually had one do that to me, a type of beetle called a darkling beetle,” she said. “I was holding it trying to get a picture and do a video of it. And when I put it down, I had this really dark purple staining on like two of my fingers, and it didn’t wash off; it actually had to wear away. And stink bugs can also do that.”
Other insects that can leave stains include millipedes and grasshoppers, Brown said.
“A lot of kids probably know about this: They talk about grasshoppers and tobacco juice. It’s not actually tobacco juice,” she said. “But essentially what they’re doing is they regurgitate this liquid up on you to, you know, get you to drop them. Because, again, it’s a defense mechanism and it’s kind of smelly and it’s like this brown, gross, slimy stuff. So, you know, it kind of is doing its job by not having you want to handle it anymore.”
Do you have a bug question for Wizzie? Drop us a line, and we’ll pass it along.