The asian hornet: threats, biology & expansion

Abstract

This was on a cold autumn day in the remote Japanese Alps back in 1987, there I discovered a massive hornet nest, just under a meter in diameter, attached to the underside of a concrete road bridge. As the air temperature was around 5°C and all insects are cold blooded, I approached the nest closely to admire its beautiful structure. However, when I tried to obtain a piece of the exquisitely designed nest envelope I was suddenly and unexpectedly attacked by several large yellow hornets that successfully chased me away. Perplexed, I returned the next evening armed with a thermometer (typical scientist), which I plunged into the nest and ran away, again being chased by some angry hornets. Then from a safe distance using a pair of binoculars I observed the temperature inside the nest rise to an amazing 30°C! Had I discovered the first warm-blooded insects? Would I get a Nobel Prize for my discovery? Well obviously-not, thermoregulation in wasps had already been described way back in 1932 by the German scientist Bernard Himmer, and as every beekeeper knows, their bees are able to carefully control the temperature within their colony. Still excited and undeterred I returned and placed more thermometers into the nest (Figure 1) and started to track the nest temperature reported in my first ever scientific publication on hornets entitled 'Thermoregulation in Vespa simillima xanthopthera', a riveting read. So, although no Nobel Prize awaited, it did introduce me to the wonderful world of social insects, a subject that I continue to find absolutely fascinating and has over the years become my life's work. Although my original postgraduate research scholarship to Japan was to study high altitude beetles, this painful encounter with a hornet colony, led to most of the next seven years I spent in Japan being dedicated to understanding the population dynamics and natural history of hornets, from up in the mountains of central Japan, down to the remote sub-tropical Japanese islands (Ogasawara islands) near Taiwan. Much of the basic information provided in this book is based on my studies into various Japanese hornet species, especially the yellow hornet (Vespa simillima), a species that is a very similar size and has the same nesting biology as the Asian hornet. In addition, I spent years conducting post-doctoral studies on several other species of hornets, including the Asian hornet all over South West Asia. Over the years, I have removed for study well over 500 hornet colonies, including the Japanese giant hornet - the world's largest species. I have supplemented this information with the increasing amount of scientific literature on the Asian hornet, personal experiences and knowledge gained from working alongside many hornet experts, especially the hornet hunters of the Japan.