The Asian hornet is considered to be a generalist predator (4), with a diet which depends on what is locally available and on the stage of the hornet colony’s development (2). Although the Asian hornet is known to be a major predator of honey bees (2) (3) (6) (8) (9), it also feeds on other insects such as wasps, crickets, butterflies and flies (2) (3) (4) (8), as well as on spiders and even vertebrate flesh (4) (8). Interestingly, the Asian hornet has also been documented eating ripe fruit (2) (3) and flowers (3).
Insect prey is usually caught on the wing (5), with the Asian hornet hovering over the entrance to a hive and catching foraging honey bees returning with nectar or pollen. The hornet forces its prey to drop to the ground before paralysing it and carrying it away (2). In this way, the Asian hornet is reported to be capable of destroying up to 30 percent of a bee colony in just a couple of hours (2). Asian hornets may also enter a honey bee hive to raid a colony (5) after attacking the honey bee guards (2). Although the worker hornets eat part of the prey themselves, most of the captured insects are decapitated, have their legs and wings removed, and are then formed into a pulp to be fed to the developing hornet larvae back at the nest (2).
Formed of six or seven separate layers known as ‘cell cakes’ and wrapped in an exterior ‘envelope’ (2), the nest of the Asian hornet is a very large (3) (4) and round structure (2) (4), and is usually slightly taller than it is wide (2). Progressively growing in size from spring until autumn, the nest can measure between 60 and 90 centimetres in height and between 40 and 70 centimetres in diameter in some parts of the species’ range (2). The Asian hornet’s nest is made up of as many as 17,000 individual cells (2), with each nest containing as many as 1,000 or more individuals hornets (2) (7). Each nest usually has just one entrance about half-way up the side, protected by a papier-mâché awning (2).
The Asian hornet has a relatively long period of seasonal activity (6), being active from about April to November, with a peak in August and September (3). At this point, fertile males will seek out young virgin queen hornets with which to mate (2). Colony activity tends to stop as winter sets in, at which time the males and workers die, and the mated queens enter hibernation (4). The average lifespan of a worker Asian hornet is only about 30 days during the summer, and about 55 days in warm spring weather (2). The queens over-winter either on their own or in groups, sheltering in cavities underneath tree bark, in plant pots or in any small, well-insulated crevice (2) (3).
Early spring sees the emergence of the mated Asian hornet queens (5), with some emerging as early as February (4), at which time the queens disperse to find a suitable area in which to nest, lay their eggs and establish a new colony (2) (4). Although little information is available to determine the exact start and end of the egg-laying period, it is thought that it may depend on temperature, with warmer weather potentially stimulating early laying activity, possibly as early as February (2). The first worker hornets begin to emerge in May, before the reproductive individuals emerge in the autumn (4). Large Asian hornet colonies are rapidly established, soon numbering several thousand individuals, many hundreds of which are mated queens. As the winter comes around and the colony dies, the cycle starts again as the mated queens seek out a place to over-winter (5).
The Asian hornet is not generally aggressive towards humans (2) (9), and in France is known to be predated by a variety of birds, particularly woodpeckers, jays and tits, which are seen pillaging nests and eating hornet larvae before the winter sets in (2).