The sound field generated by tethered stingless bees (Melipona scutellaris): inferences on its potential as a recruitment mechanism inside the hive

Abstract

SUMMARYIn stingless bees, recruitment of hive bees to food sources involves thoracic vibrations by foragers during trophallaxis. The temporal pattern of these vibrations correlates with the sugar concentration of the collected food. One possible pathway for transfering such information to nestmates is through airborne sound. In the present study, we investigated the transformation of thoracic vibrations into air particle velocity, sound pressure, and jet airflows in the stingless bee Melipona scutellaris. Whereas particle velocity and sound pressure were found all around and above vibrating individuals, there was no evidence for a jet airflow as with honey bees. The largest particle velocities were measured 5·mm above the wings (16.0±4.8·mm·s -1 ). Around a vibrating individual, we found maximum particle velocities of 8.6±3.0·mm·s -1 (horizontal particle velocity) in front of the beeʼs head and of 6.0±2.1·mm·s -1 (vertical particle velocity) behind its wings. Wing oscillations, which are mainly responsible for air particle movements in honey bees, significantly contributed to vertically oriented particle oscillations only close to the abdomen in M. scutellaris (distances р5·mm). Almost 80% of the hive bees attending trophallactic food transfers stayed within a range of 5·mm from the vibrating foragers. It remains to be shown, however, whether air particle velocity alone is strong enough to be detected by Johnstonʼs organ of the bee antenna. Taking the physiological properties of the honey beeʼs Johnstonʼs organ as the reference, M. scutellaris hive bees are able to detect the forager vibrations through particle movements at distances of up to 2·cm.

Thoracic vibrations in stingless bees (Melipona seminigra):resonances of the thorax influence vibrations associated with flight but not those associated with sound production

“…The limitations for exact measurements around foragers within the nest call for alternative methods that allow a detailed study of the signal generation and signal transmission in a controlled laboratory situation (Michelsen, 2003). Annoyance buzzing and forager vibrations are very similar in terms of the mechanism of their generation, and they result in similar vibrations of the legs and wingtips (Fig.·7), which transform thoracic vibrations into substrate vibrations and airborne sounds (Michelsen et al, 1987;Tautz et al, 2001;Michelsen, 2003;Hrncir et al, 2008). Our data suggest that thoracic vibrations are transformed into mechanical signals in both annoyance buzzing and forager vibrations with similar efficiency.…”

“…Our data suggest that thoracic vibrations are transformed into mechanical signals in both annoyance buzzing and forager vibrations with similar efficiency. Annoyance buzzing of sling-tethered bees, therefore, permits study mechanisms of signal generation and transmission under controlled conditions in stingless bees, as recently demonstrated for the transformation of thoracic vibrations into air particle movements (Hrncir et al, 2008). …”

The recruiter's excitement – features of thoracic vibrations during the honey bee's waggle dance related to food source profitability

“…Foragers generated thoracic vibrations of significantly higher velocity amplitude when collecting at high-profit food sources than when collecting at low-profit food sources (behavioural threshold low-profit-high-profit food source in this study: experiment 1: concentration ≥25% sugar w/w; experiment 2: solution flow ≥9lmin (Heran, 1959;Michelsen et al, 1987;Michelsen, 2003;Tsujiuchi et al, 2007;Hasegawa and Ikeno, 2011). In both cases, the strength of attraction over distance depends on the strength of the stimulus vibration (Morse, 1981;Hrncir et al, 2008). Thus, the observed increase in both amplitude and duty cycle of the thoracic vibrations (proportion of the waggle phase in which the bees vibrate their thorax) may enhance the attractiveness of the dancer with increasing food source profitability.…”

Vibratory Communication in Stingless Bees (Meliponini): The Challenge of Interpreting the Signals

“…Non-flight thoracic vibrations of stingless bees are transformed into airborne sound well audible for the human ear (Hrncir et al 2004a(Hrncir et al , 2008b. Since, different from us, bees do not have sound pressure receivers (Snodgrass 1956;Hrncir et al 2006a), the physical parameter most relevant for the perception of airborne sound is air particle movement.…”

“…In stingless bees, however, wings play a minor role for the transformation of thoracic vibrations into airborne sounds and medium flow, respectively. According to a detailed investigation in sling-tethered stingless bees (Melipona scutellaris), the sound field (particle movement) around a vibrating bee is predominantly generated by the oscillations of the thorax itself (Hrncir et al 2008b). Although the wings vibrate with velocity amplitudes of close to 700 mm/s along with the thorax (measured in M. seminigra; Hrncir et al 2008a), they significantly affect the vertically oriented particle velocity close to the abdomen only ( Fig.…”