Adjustment of honey load by honeybee pollen foragers departing from the hive: the effect of pollen load size

Abstract

Honeybee foragers load a small amount of honey into the crop when they leave the hive. This ''honey at departure'' is used as a material to build pollen loads (glue honey) as well as fuel during flight in pollen foragers. We investigated the relationship between the size of pollen loads that a forager collected and the amount of honey at departure in the Western honeybee, Apis mellifera. Dancing pollen foragers increased honey at departure with the size of collected pollen loads. Analysis of the waggle-run duration revealed that the size of pollen load affected the rate of increase of honey at departure with food source distance in dancers. The increase rate was significantly higher in dancers that had returned to the hive with large pollen loads versus nectar-collecting dancers, but not in those with smaller pollen loads. The higher increase rate may reflect additional fuel carried for the return trip in pollen-foraging specialists that do not use collected nectar as fuel. Although honey carried by departing dance followers also increased significantly with the size of pollen load carried by dancers, the adjustment was different from that of dancers. These results suggest that recruited bees adjust the amount of honey at departure, including glue honey, based on communicated information and modify the amount of honey load subsequently based on their own experience.

Nectar loads as fuel for collecting nectar and pollen in honeybees: adjustment by sugar concentration

“…Previous studies showed that the amount of nectar that foragers carry from the nest is adjusted by several factors, including target food type (nectar or pollen), food-source distance, and reward variability (Beutler 1950(Beutler , 1951Harano et al 2013Harano et al , 2014Harano and Sasaki 2015;Tan et al 2015). The frequency of begging trophallactic contacts with nest mates (putative reception of nectar) is also reported to change, depending on food-source profitability and variability (Núñez 1970;Farina 1996;Farina 2001, 2003).…”

“…Honeybee foragers tend to specialize in either nectar or pollen collection (Free 1960;Page 2013;Harano and Sasaki 2015). Pollen foragers not only use the nectar carried from the nest as fuel but also use it as "glue" to build pollen loads (Parker 1926;Hodges 1952).…”

“…They regurgitate part of the crop content during a foraging trip and mix it with collected pollen to give cohesiveness, which appears to be essential to build pollen loads on corbiculae. Pollen foragers carry more nectar from the nest than nectar foragers because of the need for "glue" (Beutler 1950(Beutler , 1951Harano et al 2013Harano et al , 2014Harano and Sasaki 2015). Pollen loads are composed of pollen grains and an almost equal amount of sugar (Roulston et al 2000).…”

“…First, we investigated the effect of forager subtypes, nectar, or pollen foragers. In addition to need of nectar for glue, pollen foragers may need to carry more fuel from the nest than nectar foragers, because they may not collect nectar that can be used as fuel for the return trip (Harano and Sasaki 2015). Because of their larger sugar requirement, pollen foragers might use more-concentrated nectar than nectar foragers.…”

“…Second, we investigated the effect of food-source distance on the concentration of nectar carried by foragers from the nest. Foragers increase the amount of nectar carried from the nest (Beutler 1950;Harano et al 2013Harano et al , 2014Harano and Sasaki 2015) with distance to the food source. They might also carry more-concentrated nectar to increase the sugar content of the crop load for visiting distant food sources.…”