Weird Acid-Spitting Arthropod
This page started July 20, 2002   Updated:01/29/2013

It moved with slow deliberation. It was a fine example of adaptation and camouflage. It's large size was well hidden by the shapes and colors which eons of evolution had molded into its chitinous body.  The male of its species, much smaller than the female, remained attached to the female-much like a parasite-through most of its lifetime. The female also had the ability to spray acid at anything that disturbed it. I watched it with some trepidation, wondering how I could safely move this surprise guest from our vicinity  without any harm befalling me, or it.

That sounds almost like something from a science fiction story, doesn't it? Well, it wasn't. I wrote it. And I was writing about something that had infiltrated my girlfriend's house.

Sometime around June 22, 2002, I had sent the following as an email attachment to my fellow BBSP (Brazos Bend State Park) volunteers:
"Sometimes the most innocent little event can  really teach you something!  Glen probably already knows what I'm going to talk about...but *I* didn't.  At the BBSP Visitor's Center, we currently have a large walking stick insect.  I guess it was caught in  the park, if I remember what David said correctly.  Then Ken recounted a run-in he'd had with a  "heavy-bodied" walking stick that he found out secreted  a very acidic substance. (You've got to listen to Ken. He's got all kinds of nuggets like  this.) David and I looked for some kind of identity for this creature. That's when I discovered there were *many* species of stick insects. Maybe everyone else knew this...but I didn't. Then, a search on the internet brought up a species:
Anisomorpha bupestroides
 ...and a common name, "American Walking Stick". This  was described as a heavy-bodied Phasmid (phasmids are
 insects that emulate plantforms by growing their exoskeletons to resemble plants in shape and color),  with a male about 1/2 the size of the female. This insect can secrete a powerful irritant that can cause temporary blindness. Now, this evening, a further search has uncovered a *different* common name: Two-striped walkingstick. I'd only found one picture before.
 Here is a link that shows a group of pictures of these insects."

I got an answer from  a  different volunteer which told of their experience with these same insects. These folks, however, had had a group of them which reproduced, and while releasing the last "original" female, their 5 year old child was burned when it crawled up on his shoulder and he posed for a picture. So, the Ken incident above (where he'd moved one off a tire stem by pushing it with a tire gauge, and then placed the gauge in his mouth while filling the tire and discovered the acid) and this one both seem to verify this walking stick's acidic nature.
Then, near June  22nd, which was 10 days after the email I'd sent, I was at Donna's house, and it was time to close up everything. As I checked one of the doors, I looked down, and there on the door molding was one of the walkingsticks! Donna had said that they were common there. We captured it, and I waited until the next morning to examine my "prize".  Next morning, I carefully took some pictures of my own. I haven't figured out a safe way to test  this creature's acidity, but I will.  NO, any test that requires using myself as a subject is not acceptable; just in case anyone out there was going to suggest it.  So, here are my pictures. By the way, after I'd released this pair from the end of the porch, I walked to the back door and found another pair waiting for me!  This walking stick is not the type that we'd had at the park which prompted this entire investigation.

                                      FRONT                                               SIDE                                                  REAR                                   WHAT THE HELL AM I DOING?

Sometime in 2005, I read the book For Love of Insects, by Thomas Eisner.  On pages 83-89 of the hardcover edition there is more information on this insect.
Dr. Eisner calls it a "devil's rider".  According to the book, this insect can spray up to 40 (15.75 inches)  centimeters. The spray can be aimed in all directions. The walkingstick was observed by Dr. Eisner to spray when touched. Also, the only time this walkingstick sprays when approached is when a bird (not something bird-shaped, but a real bird) approaches within 20 (7.8 inches) centimeters of the insect and the spray is used as a pre-emptive defence.  Obviously, I didn't see or smell such defence, and I was probably lucky for that. In some of Dr. Eisner's experiments, a live bird (which was unfamiliar with the anisomorpha) was presented with a walkingstick. When it attempted to eat the insect, the bird was sprayed before it got within touching distance (as I said, 20 cm or 7.85 in.). The bird was blinded and so disoriented that it fell down. The effects eventually wore off, but the the birds soon learned to ignore these walkingstick insects.  Also, the main component of the spray isn't actually an acid, but a compound called a "terpene"; which is a hydrocarbon related to terpentine, pine oil, or camphor oil (see  "toxicity, turpene" in eMedicine).  If I understand Dr. Eisner's book correctly, he and his group isolated this compound, and discovered it was new. They named it "anisomorphal".  The walkingstick manufactures this compound itself--that is, it doesn't get this chemical directly from plants in its diet.

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