DAY 10-12: The Chrysalis Formation (15 min, one day)
1. Students will begin to observe that their caterpillars are hanging from their hind "legs" from the top of their containers, forming a J, or hook-shaped position:
Signature "J-shape" of caterpillar on the verge of metamorphosis
10x
(picture taken with QX3)
My classes witnessed several of the caterpillars in this position on the 10th day of observations, although the timing is different for each caterpillar. Let them observe for themselves that this hanging position is a clue that the larvae will be shedding their exoskeletons to reveal a chrysalis, or the pupal stage, underneath. The chrysalis is the last skin of the larval stage.
2. Now it is time to set up the digital microscope. If students spot their caterpillar assuming the J-shape, they should carefully remove the cheesecloth to which it is clinging. From here they should position it on the top of a hole in a test tube rack, with the caterpillar dangling through the hole in plain view. My students developed their own microscope rig by removing the handheld portion of the microscope and attaching it by Velcro strips and masking tape to a box anchor, or stage, as seen through the screening in this picture:
You can suggest that your students try this setup or scheme up their own... I'm sure there are better designs!
Alternative: Other students set up an alternative rigging in the small net habitats for the swallowtails. They clamped a microscope to a ring stand, taping the caterpillar to a clamp above for a unique view from the bottom.
Capturing the process in time-lapse normally involves some trial and error. Once you have the QX3 aimed and focused at a hanging caterpillar, set the time-lapse function to take a snapshot every 15 seconds. The movie will run for approximately 1 hour, and can be left unattended during this time. The time-lapse will need to be reset if nothing has occurred by the end of this time period.
My students caught one of the larva turning into its pupal stage, and the rest happened over the weekend, supporting the existence of "Murphy's Law" in science!
Click this link to see their movie in Quicktime (.mov file)
Click this link to see their movie in Windows Media Player (.avi file)
This video was recorded for approximately 15 minutes during class, with the time-lapse set to take a snapshot every 30 seconds. I would suggest trying a shorter lapse time between each snapshot, as mentioned in the explanation above, to capture a smoother sequence.
During each class the next day, students watched the movie that their classmates made the day before. I had never seen the kids so interested, grossed out, and proud.
Student sketch of Painted Lady chrysalis, or pupa
