Tools...

Caring for caterpillars doesn't take much equipment. Well, a pair of scissors helps in trimming away yellowed or de-fronded fennel (or whatever member of the carrot family you're feeding them), but scissors aren't specialized enough to warrant detailed coverage here.

The major specialized tools that are used around here are pictured below:

Magnifying glass: Actually you can live without the magnifying glass, but it was cheap and anyway it's lots of fun to see your little guys/gals close-up and personal, and to examine eggs. You can even shoot digicam photos thru the lens, although this takes some practice. And, sometimes a magnified view is needed to see if a critter is moving at all. Movement, even when very slight, is a Sign of Life.

The magnifier shown above is about 2.5x (makes things look 2.5 times bigger) and is made by Tasco, model # 9555. 2.5x doesn't sound like much, but you'd be surprised at how much more detail you can see.

Popsicle stick: This is no ordinary popsicle stick...it has been modifed into a Tiny-Cater-Scooper-Upper. The mod is shown at increased magnification below:

One end of the popsicle stick has been chopped off and then beveled with sandpaper to a semi-sharp edge. The idea is to avoid using your huge klutzy whale-like fingers 

to try to pick up a tiny and fragile and squishable caterpillar that has fallen somewhere and needs to be placed back on the plant. 

Instead, use the beveled end of the stick to scoop her/him up gently (usually the cat will happily climb onto the beveled part of the stick if you place it in front of him/her), 

then bring your little buddy to the desired relocation site and let her/him walk off onto the frond. This last bit requires some patience but is important, as hurriedly wiping the cat off the stick onto the frond tends to lead to another scoop-up within a few seconds [it's amazing how a cat can manage to fall all the way thru a densely packed & tangled thicket of fennel fronds without grabbing even one of them!]. In other words, let the cat get a grip.