This bug was very active and would crawl from side to side of the tank quite fast, making it difficult to photograph him. I discovered that by touching its spines with an instrument (I used a micro-spoon), it would curl up into a ball and would remain motionless for a minute or longer. This shot shows the bug in a cryptic defensive posture. I saw this bug assume the same posture after crawling up the corner of the tank to the water's surface(perhaps to capture air); to return to the bottom of the tank, the bug assumed this curled-up posture and floated back down. I suspect it would behave in a similar way in its natural habitat.