week on ash leaves in the canopy before mating, but cause little defoliation in the process. Males hover around trees, locate females by visual cues, and drop directly onto the female to mate. Mating can last 50 minutes, and females may mate with multiple males over their lifespan. A typical female can live around six weeks and lay approximately 40–70 eggs, but females that live longer can lay up to 200 eggs. Eggs are deposited between bark crevices, flakes, or cracks and hatch about two weeks later. Eggs are approximately in diameter, and are initially white, but later turn reddish-brown if fertile. After hatching, larvae chew through the bark to the inner phloem, cambium, and outer xylem where they feed and develop. Emerald ash borer has four larval instars. By feeding, larvae create long serpentine galleries. Fully mature fourth-instar larvae are long. In fall, mature fourth-instars excavate chambers about into the sapwood or outer bark where they fold into a J-shape. These J-shaped larvae shorten into prepupae and develop into pupae and adults the following spring. To exit the tree, adults chew holes from their chamber through the bark, which leaves a characteristic D-shaped exit hole. Immature larvae can overwinter in their larval gallery, but can require an additional summer of feeding before overwintering again and emerging as adults the following spring. This two-year life cycle is more common in cool climates, such as European Russia. Range The native range of the emerald ash borer is temperate north-eastern Asia, which includes Russia, Mongolia, northern China, Japan, and Korea. The beetle is invasive in North America where it has a core population in Michigan and surrounding states and provinces. Populations are more scattered outside the core area, and the edges of its known distribution range north to Ontario, south to northern Louisiana, west to Colorado, and east to New Brunswick, and in the Pacific Northwest in Oregon. In eastern Europe, a population was found in Moscow in 2003. From 2003 to 2016, this population has spread west towards the European Union at up to per year and is expected to reach central Europe between 2031 and 2036. Although not recorded from the European Union as of 2019, it has already spread to far eastern Ukraine from neighboring Russia. Host plants In its native range, emerald ash borer is only a nuisance pest on native trees, as population densities typically do not