Antipodean Bucket Farmer said:

Hi Everybody,

I have experienced a caterpillar attack on my broccoli
and then similar-appearing damage to my cauliflower.
snip
This specific gang of perpetrators are each about a
centemetre or so long, neon-green, and walk with a sort
of "inch-worm" type wave through their body (but the
legs are obvious.) I think the butterfly version is a
small, white variety.

Cabbage loopers -- the larva of a small gray-brown night-flying moth.
They heavily prefer plants in the cabbage family but will also feed on
alfalfa, peas, beets, lettuce, and some flowers.

http://www.ipm.ucdavis.edu/PMG/r114300711.html

The cabbage white butterfly's caterpiller does not walk by hunching up.
It specializes in cabbage family members (crucifers) only.
--
Pat in Plymouth MI ('someplace.net' is comcast)

Any technology distinguishable from magic is insufficiently advanced.
(attributed to Don Marti)