What is "pear slug"

Pear \Pear\ (p[^a]r), n. [OE. pere, AS. peru, L. pirum: cf. F. poire. Cf. Perry.] (Bot.) The fleshy pome, or fruit, of a rosaceous tree ( Pyrus communis), cultivated in many varieties in temperate climates; also, the tree which bears this fruit. See Pear family, below. Pear blight.

1. (Bot.) A name of two distinct diseases of pear trees, both causing a destruction of the branches, viz., that caused by a minute insect ( Xyleborus pyri), and that caused by the freezing of the sap in winter.
   --A. J. Downing.

2. (Zo["o]l.) A very small beetle ( Xyleborus pyri) whose larv[ae] bore in the twigs of pear trees and cause them to wither.

   Pear family (Bot.), a suborder of rosaceous plants ( Pome[ae]), characterized by the calyx tube becoming fleshy in fruit, and, combined with the ovaries, forming a pome. It includes the apple, pear, quince, service berry, and hawthorn.

   Pear gauge (Physics), a kind of gauge for measuring the exhaustion of an air-pump receiver; -- so called because consisting in part of a pear-shaped glass vessel.

   Pear shell (Zo["o]l.), any marine gastropod shell of the genus Pyrula, native of tropical seas; -- so called from the shape.

   Pear slug (Zo["o]l.), the larva of a sawfly which is very injurious to the foliage of the pear tree.

The pear slug or cherry slug is the larva of the sawfly, Caliroa cerasi, a nearly worldwide pest. They are not slugs but are a kind of sawfly of the family Tenthredinidae. The pear slug is an important pest that eats leaves of cherry, pear, and plum trees, leaving behind a skeleton of veins. The larvae cover themselves in green slime, making themselves unpalatable to predators. When the larvae are fully grown, they drop off the tree on the ground and pupate underground. The adult sawfly emerges from the pupal case and climbs from the soil to mate and lays eggs on the leaves of the host plant, completing the lifecycle.

Other sources dispute the notion that the females climb the tree to lay their eggs, claiming instead that they fly to the tree. This is an important detail in regards to their control in horticultural circumstances where glues are used to control climbing pests.