Defensive biting by Tetragonisca angustula is dangerous but not suicidal
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Insectes Sociaux
RESEARCH ARTICLE
Defensive biting by Tetragonisca angustula is dangerous but not suicidal J. R. Glass1 · M. Duell2 · J. F. Harrison1 Received: 26 May 2020 / Revised: 26 September 2020 / Accepted: 21 October 2020 / Published online: 17 November 2020 © International Union for the Study of Social Insects (IUSSI) 2020
Abstract Suicidal defense is an important and effective attribute of some highly social animals. It has been suggested that the defensive behavior of biting onto raiders is suicidal in stingless bees; however, the mechanisms causing death are unclear. We conducted the first test of the effect of agonistic encounters on death and injury rates of guards of a stingless bee, Tetragonisca angustula, that bit both conspecific and heterospecific invaders within plastic tubes. Tetragonisca angustula guards bit and immobilized invading bees for long durations and had the ability to release their hold, but rarely did so unless the other bee died. In our assays, which lasted hours to up to 1 day, the probability of death during nest defense by T. angustula was 5–7%. Bitten invading bees fought back, often causing injury and sometimes death of the biting T. angustula. Tetragonisca angustula foragers can survive for 7 days without food and so death by starvation of guards during day-long encounters seems unlikely. Death rates of biting guards holding non-nestmates on the ground may be higher in the field due to susceptibility to predation. Defensive biting of stingless bees effectively protects the nest, and most guards likely are able to return to their tasks after a raid is thwarted, though studies in a more naturalistic setting are needed. Keywords Defensive behavior · Altruism · Suicide defense · Stingless bees
Introduction Some highly social animals use suicidal force to defend their territories and resources (reviewed in Shorter and Rueppell 2012). The most dramatic examples are seen in some social insects (e.g., ants, bees, wasps, and termites), which have evolved specialized weapon structures (e.g. stingers, venom, acid glands) and/or social castes (e.g. soldiers or guards) that obligatorily link defensive behavior to morphological destruction of the defender. In these species, the altruistic Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00040-020-00790-5) contains supplementary material, which is available to authorized users. * J. R. Glass [email protected] M. Duell [email protected] J. F. Harrison [email protected] 1
Arizona State University, Tempe, AZ 85281, USA
Western University, London, ON N6A 5B7, Canada
2
suicidal defenders generally do not have direct reproductive fitness, occur in relatively large numbers, and may, therefore, be expendable for the family group (Michener 1964; Nonacs 1991; Shorter and Rueppell 2012). One well-known example is the Western honey bee (Apis mellifera), whose abdomen is eviscerated when the barbed stinger and poison gland is autotomized (Hermann 1971, 1984). Sting autotomy also occurs in some
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