Ambient Temperature Influences Australian Native Stingless Bee (Trigona carbonaria) Preference for Warm Nectar

Abstract

The interaction between flowers and insect pollinators is an important aspect of the reproductive mechanisms of many plant species. Several laboratory and field studies indicate that raising flower temperature above ambient can be an advantage in attracting pollinators. Here we demonstrate that this preference for warmer flowers is, in fact, context-dependent. Using an Australian native bee as a model, we demonstrate for the first time a significant shift in behaviour when the ambient temperature reaches 34°C, at which point bees prefer ambient temperature nectar over warmer nectar. We then use thermal imaging techniques to show warmer nectar maintains the flight temperature of bees during the period of rest on flowers at lower ambient temperatures but the behavioural switch is associated with the body temperature rising above that maintained during flight. These findings suggest that flower-pollinator interactions are dependent upon ambient temperature and may therefore alter in different thermal environments.

Honeybees prefer warmer nectar and less viscous nectar, regardless of sugar concentration

“…In temperate climates honeybees have to invest energy to elevate and maintain their thoracic temperature for flight [3,4,30]. The availability of warmer nectars at lower air temperatures will aid in the maintenance of body temperature while feeding: this has been confirmed by the use of thermal imaging techniques to show that stingless bees feeding on warmer nectars are better able to maintain their body temperatures while on flowers [13]. In honeybees, Afik & Shafir [12] found that the time from stopping imbibing to flying off the artificial flower was shortest at high air temperatures, but here the effect of higher nectar temperatures cannot be separated from that of higher air temperatures.…”

“…We found that an increase in viscosity of 20% sucrose solutions resulted in a decrease in crop loads and total consumption, even though the range of viscosities used was narrow in terms of natural nectar concentrations. Viscosity has been assumed to have little effect on the intake rates of bees drinking sugar solutions below 35-40% in concentration [17,18] and was not considered in the experiments of Norgate et al [13] using stingless bees. However, the model of optimal nectar intake constructed by Heyneman [16] showed benefits of feeding at higher temperatures for nectar concentrations as low at 10%.…”

Innate colour preferences of the Australian native stingless bee Tetragonula carbonaria Sm.

“…1b within that study. Experiments were conducted at Monash University in a 3 m × 5 m controlled temperature laboratory (CT lab), set to 27 °C and 30 % relative humidity (SPER-Scientific Hygrometer, Arizona, USA) during habituation and experimental phases to allow effective foraging activity of the bees (Norgate et al 2010). Two colonies of bees were propagated by Dr Tim Heard following established protocols (Heard 1988) and housed in 28 × 20 × 31 cm (LWH) pine nesting boxes.…”

“…These bees are active year round when temperature is greater than 18° (Heard and Hendrikz 1993), and typically forage as generalists that and can learn to collect nectar from a variety of flowers (Heard 1999). Recent work shows that colour perception of T. carbonaria can be tested in laboratory conditions (Spaethe et al 2014), enabling a high level control over factors like light and temperature that easy influence stingless bee behaviour (Heard and Hendrikz 1993;Norgate et al 2010).…”

Hot Shoes in the Room: Authentication of Thermal Imaging for Quantitative Forensic Analysis

“…Similar to the cooling of the shoe, where pixel intensity decreases over time, the pixel intensity of the house of interest would slowly change until reaching the same level as their surrounding house once the power has been turned off to mislead the authorities. In this context, time estimates from thermal images can be used as evidence to corroborate witnesses' or suspects' testimonies or for cross-examination during trial, or could be used in biological and medical studies [32,33]. By implementing scientific principles to calibrate thermal imagers, these devices could be more frequently used for criminal investigation and forensic visualisation, giving law enforcers, prosecutors, and attorneys evidentiary tools that stand up to scrutiny in court.…”