Heat and carbon dioxide generated by honeybees jointly act to kill hornets

Abstract

We have found that giant hornets (Vespa mandarinia japonica) are killed in less than 10 min when they are trapped in a bee ball created by the Japanese honeybees Apis cerana japonica, but their death cannot be solely accounted for by the elevated temperature in the bee ball. In controlled experiments, hornets can survive for 10 min at the temperature up to 47 degrees C, whereas the temperature inside the bee balls does not rise higher than 45.9 degrees C. We have found here that the CO2 concentration inside the bee ball also reaches a maximum (3.6 +/- 0.2%) in the initial 0-5 min phase after bee ball formation. The lethal temperature of the hornet (45-46 degrees C) under conditions of CO2 concentration (3.7 +/- 0.44%) produced using human expiratory air is almost the same as that in the bee ball. The lethal temperature of the honeybee is 50-51 degrees C under the same air conditions. We concluded that CO2 produced inside the bee ball by honeybees is a major factor together with the temperature involved in defense against giant hornets.

Detection of Neural Activity in the Brains of Japanese Honeybee Workers during the Formation of a “Hot Defensive Bee Ball”

“…This finding suggested that Acks shares similar properties with the European honeybee neural IEG, kakusei . In addition, we also examined whether Acks upregulation after neural activation begins earlier under a higher temperature, because the temperature in the hot defensive bee ball rises to almost 47°C [6], [16]. In the bees awakened from anesthesia under the high temperature (46°C), Acks expression also peaked at 30 to 60 min (Figure 1C).…”

“…On the other hand, the formation of a hot defensive bee ball is a highly adaptive anti-predator behavior. Because there is only 3–5°C difference in the lethal temperature between the Japanese honeybee and the giant hornet [6], [16], accurate monitoring and precise control of heat generation during forming a hot defensive bee ball seem critical for the Japanese honeybees. In insect, the mechanism of temperature sensing has been studied mainly in Drosophila melanogaster and is known to depend on some transient receptor potential (TRP) channels [32]–[34].…”

Agonistic interactions between the honeybee (Apis mellifera ligustica) and the European wasp (Vespula germanica) reveal context-dependent defense strategies

“…In heat-balling the wasp succumbs to the heat inside the ball because hornets and wasps have a lower thermal tolerance than bees [30,31]. In asphyxia-balling , the heat inside the ball can be lethal to the predator but it dies due to the increased concentration of CO 2 in the hemolymph which causes asphyxiation [32,33]. …”

Functional Expression and Characterization of Dipeptidyl Peptidase IV from the Black-Bellied HornetVespa basalisin Sf21 Insect Cells

“…5), similar to previously reports. 15,21,22) On the basis of some reports, 15,23,24) we speculate that the optimal activity for rDPP-IV involves important physiologic mechanisms of V. basalis, such as defense or antagonist of the external stress.…”