Millipedes and Boa Constrictors

I spent part of the weekend trying to fix the aquarium so my millipedes will stop dying. Internet research reported that they were very easy to take care of, didn't carry any known bateria or viruses that were harmful to man, and unless you ate one or got some of the mild toxin they might emit in a cut or your eye, they would not harm you. Sounded like the perfect science lab pet. I'm beginning to question my research as I am having a heck of a time keeping them alive. Hopefully none of the students catch something from the creatures.

My favorite 'beastie loose in the classroom' story goes back to when I was science specialist at a school in Caracas (1992-96) . The maintenance crew was always bringing me creatures they found - scorpions, tarantulas, snakes, .... Once they brought in this half-meter long snake which I thought was a constrictor except the snake's pupils were slit and the head was slightly triangular. This was pre-Google days, so getting a definite identification on the snake was taking awhile. Maintenance was assuring me it was a constrictor, and the snake was not aggressive.
 I had been working with another teacher on a project where students were designing and building cages for snakes. I put the snake in what I considered the best designed cage. It had a very heavy lid and a series of sliding doors and ramps for putting in food and water and removing soiled matter from the bottom of the cage, so you never had to put your hand in the cage.
When I came in the morning after receiving the snake, it was gone. I didn't calculate the strength of the snake to just lift the lid off the cage. I went and told the principal, and we cancelled science classes while I tore the lab apart. No sign of the snake. I figured it must have escaped under a door onto a balcony and then back to the jungle that came down the side of a mountain behind the school.
About a week later I was setting station activities in the lab. I had an old (even then) Apple II-E computer that had some science games on it. I pulled the cover off the computer and there coiled on the keyboard was the snake. My heart stopped and I did not need an extra cup of coffee that morning. I scooped the snake up in a net I kept handy and set it free on the mountainside behind the school.
I've since read that a pupil with a vertical slit is a sign of a venomous snake, but that snakes have no eyelids, so in order to protect their eyes from bright light, and when they're sleeping, all snakes' pupils contract to slits. Also certain constrictors heads are definitely triangular shaped with a vertically slit eye.