Body size, metabolic rate and diapause in the oriental hornet (Vespa orientalis), in two extreme climatic regions

Abstract

Temperature and precipitation are major components of climate that have a pervasive effect on the phenotype and physiology of insects. The Oriental hornet has a wide geographical distribution and is the only vespid species found in a desert environment. Recently, it has extended its geographic distribution due to climate change and human activities. We compared the standard metabolic rate, diapause metabolic rate and body size of workers and gynes in two different climatic regions, 150 km apart along the northern part of the Great Rift Valley in Israel: In the north, high elevation Mediterranean habitat and in the south, low elevation, warm and dry desert. The brood in the desert region developed in higher ambient temperatures than in the Mediterranean, but only the workers of the desert had a smaller body size as adults. Worker hornets from the Mediterranean region had a higher standard metabolic rate (SMR) at the environmental temperature of main activity compared to desert hornets. Queens had a typical discontinuous gas exchange cycles (DGC) pattern, with Mediterranean queens having a 30% lower SMR. Such lower SMR might reflect an adaptation for prolonged and more profound diapause typical to the cold and long winter conditions in this region.