Flight performance
Hornets and honey bees had different flight performances in term of
flight speed, curvature and static flight (Figure 3 ). Honey
bees leaving the hive were 1.9 times faster than honey bees entering the
hive, and honey bees entering the hive were 1.25 times faster than
hornets (Kruskal-Wallis chi-squared=78018, df=2, P<0.001;
Pairwise Wilcoxon test, P<0.001; Figure 3a ). With
respect to flight curvature, the flight trajectories of honey bees
leaving the hive were significantly. straighter than for honey bees
entering the hive, and for the latter the trajectories were
significantly straighter than for hornets (Kruskal-Wallis
chi-squared=41384, df=2, P< 0.001 ; Pairwise Wilcoxon test,
P<0.001). Moreover, the curvature was less variable in honey
bees leaving the hive compared with the two other categories
(Figure 3b ).
Hornets hovered significantly for more time than honey bees
(p<0.001 (Pairwise Wilcoxon test), hornets hovered 2.1 times
more than honey bees entering the hive). Honey bees leaving the hive
hovered significantly less than the honey bees entering the hive
(Kruskal-Wallis chi-squared=27949, df=2, P<0.001; Pairwise
Wilcoxon test, P<0.001) (Figure 3c ). In hovering
hornets, static flight as defined by “threshold 1” (no more than 2mm
displacement) represented a very small proportion of flight time, under
10%, while if defined by “threshold 2”, up to 10mm displacement,
hovering hornets can be divided into mainly two categories. A smaller
group of hornets, spending 10% of recorded flight time hovering, and a
larger group of hornets spending around 90% of recorded flight time
hovering, demonstrating that this kind of flight pattern is used by many
for long periods of time in front of the hives (Figure S2 ).