Dormancy in laboratory-reared Asian longhorned beetles, Anoplophora glabripennis

<p>An insect's capacity to survive winter is critical for range expansion in temperate regions. The Asian longhorned beetle (<em>Anoplophora glabripennis</em>) is a polyphagous wood-boring insect native to China and the Korean peninsula and poses a high risk of invasion in North America and Europe. It is unclear whether <em>A. glabripennis</em> enters diapause, which means that diapause cannot be included in assessments of the risk of this species invading forests in temperate regions. Using a laboratory colony, we examine larval developmental arrest, metabolic rates, gas exchange patterns, thermal sensitivity, and body composition to characterize larval dormancy. Chilled larvae entered a temperature-independent developmental arrest which usually required more than four weeks of chilling to break, decreased their metabolic rate by as much as 63 %, and maintained energy stores throughout the chilling period – results consistent with an obligate diapause. We also observed a switch to discontinuous gas exchange at low temperatures. Thermal sensitivity of metabolic rate did not differ between chilled and non-chilled larvae. Taken together, we conclude that <em>A. glabripennis</em> enters a larval diapause during chilling and terminates diapause after a requisite chilling period. These results will enhance our ability to predict phenology and potential distribution of current and future invasions of <em>A. glabripennis</em>. An insect's capacity to survive winter is critical for range expansion in temperate regions. The Asian longhorned beetle (<em>Anoplophora glabripennis</em>) is a polyphagous wood-boring insect native to China and the Korean peninsula and poses a high risk of invasion in North America and Europe. It is unclear whether <em>A. glabripennis</em> enters diapause, which means that diapause cannot be included in assessments of the risk of this species invading forests in temperate regions. Using a laboratory colony, we examine larval developmental arrest, metabolic rates, gas exchange patterns, thermal sensitivity, and body composition to characterize larval dormancy. Chilled larvae entered a temperature-independent developmental arrest which usually required more than four weeks of chilling to break, decreased their metabolic rate by as much as 63 %, and maintained energy stores throughout the chilling period – results consistent with an obligate diapause. We also observed a switch to discontinuous gas exchange at low temperatures. Thermal sensitivity of metabolic rate did not differ between chilled and non-chilled larvae. Taken together, we conclude that <em>A. glabripennis</em> enters a larval diapause during chilling and terminates diapause after a requisite chilling period. These results will enhance our ability to predict phenology and potential distribution of current and future invasions of <em>A. glabripennis</em>.</p>