Taken from Sydney's trip journal with minor editorial changes:

Suddenly Sydney started screaming to stop the bike and she
stopped steering. The bike went off the sidewalk before she
figured out she was the only one with a steering wheel or brakes.
She screamed for Chris, who was sitting next to her, to help. He
looked over and at her and said, "Umm, Kim go help!" Kim jumped out
and ran to Sydney who pointed to her lap. It looked like a four inch
long green bug on Sydney's inner thigh!

As Kim was trying to brush it off, Syd was screaming at the top of her lungs
and Wes drove up to see what was going on. He was looking at Syd and not
watching where he was going and almost ran over Kim's feet with his front tire.

After the initial panic wore off, we realized that it wasn't a bug but a piece of cactus!
Kim got it off but it left a long thorn in her leg. After several tries, Kim got it out
but was worried the rest of the trip that she would be arrested considering the circumstances.
We could never figure out how it got there. Syd apologized to Chris for laughing at his having
sat in a cactus patch on a prior trip.