The larvae are usually an olive green, sometimes tinged with a muddy orange with the shiny exterior that makes them reminescent of a recent bird dropping. Presumably, this unusual appearance helps them avoid predation, which is particularly important since they almost always feed on the upper surface of the leaf, well exposed. There are two generations of pear slugs. The current larvae will complete development and move to the base of the plant where they will pupate. Adults of these usually emerge again in late August and September to produce a second cycle of feeding injury.
Pear slug is extremely easy to kill with almost any insecticide.
It is also very susceptible to soapy water, although many of the hosts on which it feeds can be injured by soaps. My personal preference is to lightly dust the pear slug larvae with some wood ashes, which turns them into toasty strings within a short period. Where trade names are used, no discrimination is intended, and no endorsement by the cooperative extension service is implied.