Nocturnal windborne migration of ground beetles, particularly Pseudoophonus griseus (Coleoptera: Carabidae), in China

Abstract

Abstract1 A network of light‐traps, an aerial net carried by kytoon (balloon) and two entomological radars were used to investigate whether ground beetles migrate nocturnally through China. The network‐wide, simultaneous sudden increase in light trap catches, and after subsequent decrease, indicated a seasonal long‐distance night migration of ground beetles, with Pseudoophonus griseus (Panzer) predominant, in August.2 Aerial net trapping indicated that carabids were able to ascend to altitudes of at least 200 m and become windborne. Radar observations indicated that the migratory beetles formed high‐density layer concentrations at approximately 200–300 m.3 These concentrations were coincident with the top of the temperature inversion and a wind speed maximum, which suggested that the carabids tended to select warm, fast moving air for their long‐distance migration.4 The ground beetles orientated and displaced towards the downwind direction in southerly winds. Their air speed decreased as the tailwind increased and, thus, migrating beetles appeared to be conserving energy.5 The mean ± SD displacement speed (ground speed) and air speed were 6.85 ± 1.73 m/s (n= 172) and 4.45 ± 1.54 m/s (n= 172), respectively. The duration of flight, estimated from the variation in area density derived from radar data, was approximately 9–10 h, indicating that the beetles might migrate hundreds of kilometres in a single flight.