Timing and size of daily pollen meals eaten by adult females of a solitary bee (Nomia melanderi) (Apiformes: Halictidae)

Abstract

-Pollen feeding by solitary bees has been studied mainly with their larvae, overlooking pollen feeding by adults. To address this knowledge gap, we determined the amounts and temporal (daily and lifetime) schedules of pollen consumption by freely nesting, adult females of the alkali bee (Nomia melanderi , Halictidae). Nesting females of known ages were taken at different hours of the day from nesting aggregations managed for alfalfa pollination in southeastern Washington State (USA). Each dissected bee was visually scored for pollen fill of the crop, midgut, and hindgut; we also quantified the crop's pollen capacity. Our dissections of 188 bees show that adult females ate pollen daily for at least the first 2 weeks following emergence. Most bees (85 %) had pollen boluses in one or more gut regions, indicating active pollen feeding. Pollen masses were most likely in the midgut; the daily volume consumed usually filled both the crop and midgut at least once. Full crops contained 34,000 alfalfa pollen grains, equivalent to <20 % of a full scopal load and 0.8 % of the pollen in a nest provision. Proportionately more females ate pollen as the day progressed, indicated by pollen masses in the crop. By early evening, crops of all bees were filled with pollen. Our study reveals the dietary importance of regular pollen feeding for nesting adult female solitary bees, and not just their larvae, with implications for bee foraging ecology, dietary physiology, reproduction, toxicology, and pollination ecology.Apiformes / Apoidea / bees / Hymenoptera / foraging

Juvenile hormone, but not nutrition or social cues, affects reproductive maturation in solitary alkali bees (Nomia melanderi)

“…Our results are in contrast to results of similar studies of solitary bees in the family Megachilidae, Osmia 263 californica and Megachile rotundata, which showed access to dietary protein is essential for 264 reproductive maturation among newly emerged females (Cane, 2016;Richards, 1994). Unlike alkali 265 bees, Osmia overwinter as adults, begin oogenesis prior to eclosion, and thus eclose with depleted 266 protein stores (Wasielewski et al, 2011).…”

“…If mating is a reproductive limitation in alkali bees, it can apparently be 256 overridden by JH treatments, as some JH-treated females in our study reached reproductive maturity, 257 even in the absence of mating or ecological cues. Regardless of the role of dietary protein in the 258 initiation of reproductive activation, the fact that alkali bees and other closely related halictid bees 259 consume pollen on a daily basis suggests that protein is likely necessary for sustained reproductive 260 activity throughout the breeding season (Cane et al, 2016;Wuellner, 1999). 261…”

Support for the reproductive ground plan hypothesis in a solitary bee: links between sucrose response and reproductive status

“…The mean + 1 s.d. time between capture and treatment was 2.04 + 0.02 h. Alkali bees cease foraging activity by 19.00 [49], and do not store food in their nests [50]. All bees had thus experienced a natural starvation period of at least 19 h at the time of testing.…”

Pollen Protein: Lipid Macronutrient Ratios May Guide Broad Patterns of Bee Species Floral Preferences

“…Nectar provides foraging bees with their main source of carbohydrates [12], while pollen is the main source of proteins and lipids for bees [13]. Pollen must be consumed by larvae for proper development (or consumed by nurse honey bees to produce royal jelly), while consumption by female adults is essential for reproduction [14,15] and is linked to health and disease resistance [16]. Plant species vary widely in pollen quality including protein concentration [17][18][19][20], amino acid composition [21], lipid concentration [18][19][20]22], fatty acid profiles [23], sterol composition [24,25], and secondary metabolites reviewed in [26].…”