Behaviour of Vespa velutina nigrithorax (Hymenoptera: Vespidae) under Controlled Environmental Conditions

Abstract

From its introduction in Europe, Vespa velutina nigrithorax has become an invasive species, since it is a predator of native fruits and insects, most of the latter being honeybees. Despite the knowledge on the life cycle of this hornet, Asian hornet behaviour is not well understood, since in vivo studies on this species are quite difficult to perform. In this work, an observational study of the behaviour of this invasive species in captivity has been carried out. Two secondary and one embryo nests were caught and kept under controlled environmental conditions, up to 13 weeks for the secondary nest and 6 weeks for the embryo nest. Captivity adaptation, defence against perturbations, evolution of the colony and overwintering were the different behaviours studied. The study has shown the importance of avoiding disturbances to the nest from the beginning of the experiments, since they tend to destroy the colony. The aggressive behaviour observed in the embryo nest was lower than in the secondary nests. Results of this research will allow obtaining additional information on this species, which is crucial to develop effective control methods.

Keywords: Vespa velutina nigrithorax; behavioural study; embryo and secondary nest.

Figure 1

Life cycle of Vespa velutina hornet.

Figure 2

Location of the Basque Country in Europe (left). Map of the Basque Country, with its three counties (right). The numbers indicate the locations of the Vespa velutina supplied nests. Image modified from paintmaps.com (accessed on 4 September 2022).

Figure 3

Scheme of the cage used for the captivity study of Vespa velutina.

Figure 4

Adult Vespa velutina hornet removing a larva from the nest, with another previously removed larva.

Figure 5

Vespa velutina female hornets fighting each other shortly after the nest was collected.

Figure 6

Embryo nest of Vespa velutina in the captivity cage after 2 days of adaptation.

Figure 7

Vespa velutina hornet taking food from the impregnated paper on the ceiling.

Figure 8

Newly born in captivity Vespa velutina with the characteristic whitish colouring of the first days after hatching (a). Attacked male Vespa velutina hornet with some of its legs and wings lost (b).

Figure 9

A couple of Vespa velutina from Nest 1 mating in captivity.

Figure 10

Vespa velutina hornets from nest 1 in state of lethargy in captivity.

Figure 11

Vespa velutina male hornets in the nest.

Figure 12

Combs from the first nest organized in order of formation: 1: first, 2: second, 3: third, 4: fourth, 5: fifth and 6: the last comb formed. (From upper to bottom).

Figure 13

Nest individuals found after captivity studies. Operculated larvae that did not hatch (a), new hornets which did not emerge from the nest (b) and dead larvae (c).