This is a larva of an emerald ash borer. The larvae are the destructive stage of the pest.

EAB larvae feed in S-shaped tunnels, called galleries, in the phloem of the tree. The phloem is between the rough outer bark and the hard sapwood. Phloem transports nutrients within the tree.

As larvae grow they may also score the outer surface of the wood. This damages the xylem tissue, which transports water within the tree.

EAB adults are present from late May through August. They are roughly a half-inch long and dark metallic green. They feed on ash leaves throughout the 3-6 week life span. Their feeding does not damage or affect the tree.

Adults mate on the ash trees, after having fed for at least a week to build up their energy and complete maturation.

Eggs are laid on the surface of the bark, in bark cracks and crevices or just under the outer bark of ash trees. The eggs, which are very small and reddish-brown, may be laid in groups or individually.

Eggs hatch in 2-3 weeks and the larvae immediately begin chewing through the outer bark to the phloem. Larvae begin feeding in late July, but most feeding and growth occur from August to October. Larvae feed in S-shaped tunnels, called galleries, in the phloem. As the larva feeds and grows, the galleries get larger. The galleries disrupt the transport of nutrients and water within the tree.

Most larvae overwinter as prepupae in cells found about a half-inch into the sapwood or outer bark.

In spring, the prepupae go through pupation and become adults. It usually takes 2-3 weeks for EAB pupae to become adult beetles.

Beginning in May and continuing through June, the adult emerald ash borers emerge from under the bark. Each adult leaves a D-shaped exit hole in the bark.