The effect of photobleaching on bee (Hymenoptera: Apoidea) setae color and its implications for studying aging and behavior

Abstract

Abstract. Historically, bee age has been estimated using measurements of wing wear and integument color change. These measurements have been useful in studies of foraging ecology and plant-pollinator interactions. Wing wear is speculated to be affected by the behaviors associated with foraging, nesting, and mating activities. Setal color change may be an additional parameter used to measure bee age if it is affected by sun exposure during these same activities. The objectives of this study were to experimentally assess the effect of direct sun exposure on setal color, unicellular hair-like processes of the integument, and determine whether wing wear and integument photobleaching are correlated. To quantify photobleaching of setae, we measured changes in hue of lab-reared Bombus huntii Greene (Apidae) exposed to natural sunlight. We found that sun exposure was a significant variable in determining setal bleaching. To assess the relationship between wing wear and setal photobleaching, we scored wing wear and measured setal hue of B. huntii, Melecta pacifica fulvida Cresson (Apidae), and Osmia integra Cresson (Megachilidae) from museum specimens. Wing wear and setal hue values were positively correlated for all three species; however, the strength of the relationship varies across bee species as indicated by correlation coefficient estimates. Our results suggest that setal color change is affected by sun exposure, and is likely an accurate estimate of bee age. We suggest that future investigations of bee aging consider a suite of morphometric characteristics due to differences in natural history and sociobiology that may be confounded by the use of a single characteristic.

Neotropical stingless bees display a strong response in cold tolerance with changes in elevation

“…com). Then, we used the eyedropper tool with a 31 by 31 average pixel radius in Adobe Photoshop (Adobe, San Jose, CA) to sample the RGB color model (red, green, blue) and then transformed them to a HSL color model (Koch et al, 2014).…”

Exoskeleton ageing and its relation to longevity and fecundity in female Australian leaf insects (

“…Following the adult moult and full sclerotisation, the pigmentation and colouration of the adult insect body is generally assumed to remain constant. However, there is evidence of age-related changes in pigmentation in the exoskeletons of ants and bees (Koch et al 2014;Hartmann et al 2019) (Lim and Li 2006;Taylor et al 2014). Our results show that age-related changes in pigmentation can also occur on the wings of adult phasmids.…”

“…Adult insects also have the potential to change colour as they age as a consequence of changes in the cuticle or epidermis. The potential for age-related colour changes in adult insects is illustrated by increasing cuticle pigmentation in the ant Platythyrea punctata (Hartmann et al 2019), and bleaching of the setae in the bee Bombus huntii (Koch et al 2014), as well as gradual loss of red hue in the wings of Heliconius melpomene butterflies (Dell'Aglio et al 2017). Such changes could be maladaptive manifestations of senescence (e.g.…”

Estimating the age ofHeliconiusbutterflies from calibrated photographs

“…Age-dependent colour change has also been found in the tissues of a pentatomid bug, Halyomorpha brevis , with the change in red stronger in males ( Niva & Takeda, 2002 ). Similar colour fading was found as a consequence of direct sun exposure in bees, Bombus huntii , which colour hue was correlated with wing wear and therefore could be a reliable measure of age ( Koch et al, 2014 ). In butterfly wings, age-based colour fading has also been shown in Colias eurytheme , in which fading of structural colour was the most accurate predictor of male age.…”