Vespa velutina, or Asian yellow-legged hornet, was accidentally introduced from China to other parts of the world: South Korea in 2003, Europe in 2004, and Japan in 2012. V. velutina represents a serious threat to native pollinators. It is known to be a fierce predator of honey bees, but can also hunt wild bees, native wasps, and other flying insects. When V. velutina colonies are developed, many hornets capture foraging bees which are coming back to their hives, causing an increase in homing failure and paralysis of foraging thus leading to colony collapse. The hornets may enter weak beehives to prey on brood and pillage honey. Unlike Apis cerana, Apis mellifera is unable to cope with the predation pressure of V. velutina. Monitoring the spread of an invasive alien species is crucial to plan appropriate management actions and activities to limit the expansion of the species. In addition, an early detection of V. velutina in areas far away from the expansion front allows a rapid response aimed to remove these isolated populations before the settlement of the species. Where V. velutina is now established, control measures to prevent colony losses must be implemented with an integrated pest management approach.

The yellow-legged hornet Vespa velutina Lepeletier, accidentally introduced into France in 2004, is rapidly colonizing other European countries. In Italy the species is spreading throughout the northwest part of the country.Setting up management plans for controlling invasive alien species requires the understanding of the spread modalities and distribution range of the species, information currently not available for the yellow-legged hornet in Italy. Aims of this work are to reconstruct the spread of the yellowlegged hornet from its first arrival in the country, evaluating its distribution range and spread modalities.The area occupied by the species increased from 205 km 2 in 2013 to 930 km 2 in 2015. In 2015 the frontline of the species was at 55 km along the coast from the French border, with a linear spread of 18.3 ± 3.3 km/year. A human-mediated dispersion could be recognized in different occasions. A cluster analysis of the range allowed the identification of 17 core areas used by the species, with a mean nest density of 2.9-3.5 nests/km 2 . These information are fundamental to improve control plans and to establish an early warning and rapid response system for the yellow-legged hornet in Italy, and therefore setup an effective management plan for the species.

The yellow‐legged Asian hornet is an invasive species of wasps, indigenous to the Southeast Asia but recently spreading in Southern Europe. Because of its exponential diffusion and its serious threat to the local honeybee colonies (and to humans as well), restraint measures are currently under investigation. We developed and tested an harmonic radar capable of tracking the flying trajectory of these insects, once equipped with a small transponder, in their natural environment. Several hornets were captured close to a small cluster of honeybee hives, tagged with different transponders and then released in order to follow the flight toward their nest. On‐field testing proved an initial maximum detection range of about 125 m in a hilly and woody area. A number of detections were clearly recorded, and preferential directions of flight were identified. The system herein described is intended as a first low‐cost harmonic radar; it proved the capability to track the hornets while flying and it permitted to test the tagging techniques. Several upgrades of the system have been identified during this work and are extensively described in the last chapter. The designed system has three major advantages over conventional harmonic radars. First and most importantly, it adopts advanced processing techniques to suppress clutter and to improve target detection. Second, it allows radar operations in complex environments, generally hilly and rich in vegetation. Finally, it can continuously track tagged insects (24/7) and in any meteorological condition, providing an effective tool in order to locate the nests of the yellow‐legged Asian hornet.

The yellow-legged hornet Vespavelutina is an invasive alien species in many areas of the world. In Europe, it is considered a species of Union concern and national authorities have to establish surveillance plans, early warning and rapid response systems or control plans. These strategies customarily require the assessment of the areas that could be colonised beyond outbreaks or expanding ranges, so as to establish efficient containment protocols. The hornet is spreading through a mix of natural diffusion and human-mediated transportation. Despite the latter dispersion mode is hardly predictable, natural diffusion could be modelled from nest data of consecutive years. The aim of this work is to develop a procedure to predict the spread of the yellow-legged hornet in the short term in order to increase the efficiency of control plans to restrain the diffusion of this species. We used data on the mean distances of colonial nests between years to evaluate the probability of yellow-legged hornet dispersal around the areas where the species is present. The distribution of nests in Italy was mainly explained by elevation (95% of nests located within 521 m a.s.l.) and distance from source sites (previous years’ colonies; 95% within 1.4–6.2 km). The diffusion models developed with these two variables forecast, with good accuracy, the spread of the species in the short term: 98–100% of nests were found within the predicted area of expansion. A similar approach can be applied in areas invaded by the yellow-legged hornet, in particular beyond new outbreaks and over the border of its expanding range, to implement strategies for its containment. The spatial application of the models allows the establishment of buffer areas where monitoring and control efforts can be allocated on the basis of the likelihood of the species spreading at progressively greater distances.

The yellow‐legged Asian hornet is an invasive species of wasps, indigenous of the South‐East Asia but quickly spreading in Southern Europe. Because of its exponential diffusion and its serious threat to the local honey bee colonies and to humans as well, restraint measures are under investigation. Among them, the harmonic radar described in (Ecology and Evolution, 6, 2016 and 2170) already proved to be a quite effective way to follow the hornets to their nests; it is in fact capable of tracking the flying trajectory of these insects, once equipped with a small transponder, in their natural environment. The aforementioned harmonic radar was upgraded after a period of intense experimentation; the capture of the hornets was enhanced as well, and other improvements were adopted in the mounting procedure of the transponder. Thanks to these upgrades, the flying capabilities of the hornets were not reduced and a huge collection of data was recorded. The main upgrade to the radar was the adoption of the vertical polarization of the radiated field, with the consequent redesign and manufacturing of the antennas and the different mounting of the transceiver on the insect. The installation of the radar on a telescopic tower drastically improved the maneuverability of the system and the capability to follow the insects’ preferential flying directions. Eventually, the system was able to produce much more continuous traces with a clear indication of the most probable position of the nest. The maximum range of detection was also increased to 150 m.