Backyardsafari's Blog

Environmental Inspiration in Your Own Backyard

Purple Beetle Catchers July 14, 2010

* Edited to include more information*.


Have you seen me?


Recently, while driving around the state of Pennsylvania, I started noticing these purple boxes, high up in trees spaced out along major highways. I saw them on the way to Philadelphia, Virginia, New York, and along roads in the small rural area where I work.

Every time I saw one I wondered what it was for. My theory was that they were part of a scientific study collecting some insect to get an idea of how many were in an area. Having completed research projects myself before, this seemed to make sense–the purple boxes were spaced out fairly evenly, as if to get a solid data set, and were put along major roads I assumed because of their accessibility. I didn’t know what insect they were trying to capture/count, but with their size and height in the trees it made sense that it would be one of our six-legged flying friends.

I always meant to look up the answer but kept forgetting, as so often happens in life. Finally, on a recent bus ride, I saw a box out my window and decided to end the mystery once and for all. Thanks to the joys of 3G and my phone data plan, I was able to google search right then and there. I couldn’t find anything at first, but after trying a few different search terms before typed in “purple beetle catchers along roads” and viola! An article from a Vermont newspaper came up that explained that these purple ‘boxes’ are being used to trap the emerald ash borer beetle.

The beetle turns out to be an invasive species introduced from Asia to Michigan in 2002. It has since spread to at least 12 states and a few Canadian provinces, including Pennsylvania, New York, and Virginia. The adult beetles eat the leaves while the larva destroy the inner bark, which ruins a tree’s ability to move nutrients around. It seems this beetle has killed many millions of trees since 2002, and scientists are trying to find ways to eradicate it.

I contacted a colleague of mine at the Pennsylvania Department of Conservation and Natural Resources to find out more information. He says that usually these traps contain a pheromone inside that attracts the insect, but in this case they actually contain oil from the Manuka tree, which has compounds similar to what ash trees release when they are stressed out (which in this case is because they are being eaten by the beetles). He added that the purple color is also an attractant in this beetle family, which is why the color was chosen. The traps are not supposed to eradicate the beetle, but are helping to find out where the beetle is and monitor its movements. It seems the biggest concern is spreading the borers around through fire wood. If people cut wood infested with the borers and then take the wood somewhere else, a new area can become infested. Many thanks to Jeff at PA DCNR for the information!

This post isn’t just about the emerald ash borer, or the purple traps, though. It is about trying to ask questions about the world around us and then follow through with the answers, even though we are busy and it is hard to remember. I always find it interesting to compare the differences between adult and childhood education.  As kids, we are taught many things. When we ask why, we are told that we might need it later, or that it is part of becoming a well-rounded person. When we grow up, though, this stops. Once you get out of college, especially, continuing education either stops completely or becomes pinpointed to a very specific topic that compliments our jobs and careers. Why? Do we assume that we now are well-rounded people and don’t need to learn anything else? Do we stop becoming curious about the world around us?

I thought consciously about this for the first time in 2005, when I was keeping a notebook during field work in Wyoming. For the first time I took the usual questions that often flit in and out of our heads–I wonder what that insect is? What is the name of this? Why is this happening?–and actually wrote them down and tried to find the answers later.

It can be difficult to remember to do this, but it is a great exercise and one that enriches and compliments our usual daily routines. When I finally picked the right set of search words to find out about the emerald ash borer, I was so excited–and as funny as it sounds, proud–about finally solving this mystery. Because of it, I know more about the world today than I did yesterday.

Imagine–there is a whole drama unfolding in the forests all around us! A stow-away from another land silently devouring trees from the inside out, as teams of scientists try to fight them in an ongoing country-wide arms-race between the beetle’s adaptations and our own human technologies.

And to think I knew nothing about it!


Have you seen one of these traps near your house or in your travels? If so leave a comment or send an e-mail to–I would love to know how wide-spread these are!



3 Responses to “Purple Beetle Catchers”

  1. Dick Says:

    jguly 25, driving from Elmira N,Y, tp Md, we noticed the boxes along Rt 14
    elmira to williamsport, and then on rt 15 to harrisburg. The majority were on Rt 14 and o rt 15 close to williamsport

    • Thanks for visiting the blog and thanks especially for the sighting info! I’m interested to see how widespread these are, so it’s great to have this information. I appreciate you taking the time to let me know.

      Hope you stop by again sometime!
      -Backyard Safari

      • Don Says:

        Was also curious after seeing quite a few hanging along interstate 81 north of Harrisburg, PA just today. My sister with me saw them near Charlottesville VA where she lives earlier this week. Saw one in someone’s front yard along PA 645 just north of interstate 78 and stopped to investigate. I could see that it was sticky and had quite a few bugs on it. I noticed that it was hanging on an ash tree. I had remembered hearing that there was something attacking the ash trees and made a guess. I think I searched purple bug catchers and your site came up second. Thanks for the info!

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