Orange-legged Furrow Bee

Halictus rubicundus

"Halictus rubicundus" is a species of sweat bee found throughout the Northern Hemisphere. "H. rubicundus" was introduced into North America from the Old World during one of two main invasions of "Halictus" subgenera. These invasions likely occurred via the Bering land bridge at times of low sea level during the Pleistocene epoch.
Enjoying the Spring Sunshine and Pollen. I am once again going out on a limb with the ID of this bee. These bees are enjoying the pollen of the pussy willows in our back yard. One of the identifying features of this species of Halictus is the end segments of their legs are yellowish. Their common name, Sweat Bee, comes from this genus of bees landing on people and “drinking” the sweat from humans! Another interesting feature of these bees is that they collect pollen on the entire length of their legs giving them the name “pollen pants”.  Canada,Geotagged,Halictus rubicundus,Spring,Sweat Bee

Appearance

Many members of the family Halictidae are metallic in appearance but "Halictus rubicundus" are not metallic. Females are about 1 cm in body length and brown in color, with fine white bands across the apices of the abdominal segments, and rusty-orange legs. The males are more slender, with longer antennae and yellow markings on the face and legs; they can be distinguished from males of similar species by the absence of an apical hair band on the terminal abdominal segment. In social populations, females of the first brood, mostly workers, can be recognized because they are typically slightly smaller than the foundresses.
small hair yellow legged bee Halictus sp. I found a key to western species... it eliminated H. ligatus and I'm willing to bet on H. rubicundus over H. farinosus because of the narrow stripes on the abdomen.  Geotagged,Halictus rubicundus,Summer,United States

Distribution

"H. rubicundus" has one of the widest natural distributions of any bee species, occurring throughout the temperate regions of the Holarctic region. It is believed that differences in climate across this vast range actually contribute to variation in their social behavior. Those living in more northern geographic locations or higher elevations are often more solitary in behavior than those in southern areas or lower elevations. This difference is widely studied, as it provides insight into the evolutionary transition from solitary to social behavior. Nests are haplometrotic, meaning that they are founded by single females. Social populations typically are found in warmer regions, such as Kansas, while solitary populations nest in cooler regions, such as Colorado, Scotland and Alaska. In intermediate regions, such as New York and southern Ontario, both social and solitary behavior can be found in different nests of the same population. The strictly solitary phenotype is expressed as a response to colder environments because the active season is not long enough to produce two broods.
Large sweat bee, contemplating Halictus rubicundus on Phacelia tanacetifolia, bee's friend Geotagged,Halictus rubicundus,Spring,United States

Behavior

The annual cycle differs slightly for eusocial and solitary populations, in terms of the number and sex ratios of offspring born in the broods. For example, in solitary populations, the first brood comprises 40% females, who are all able to mate before the next hibernation season. However, in eusocial populations, the emergence from hibernation occurs one or two months earlier, and results in a brood with mostly or exclusively worker females, with the female bias being greater the earlier nesting begins. Nesting for solitary populations begins in late May or June. The absence of a brood of female workers defines this nest type as solitary, so solitary populations produce only one reproductive brood that is provisioned by a gyne. The emergence of this brood is at approximately the same time as the emergence of the second or third brood in the social colony cycle. Upon emergence, the offspring mate and then females enter hibernation away from the nesting site. As in social colonies, the males and nest foundresses die at the end of the season."Halictus rubicundus" is widely studied for their variability in behavior depending on geographic location, and with changes in temperature. Those at low elevations are known to exhibit eusocial behavior, while those at high elevations and latitudes are known to be solitary.Like most bee species, mating in "H. rubicundus" occurs on the ground or vegetation in and around the nest aggregation. Males may hover around their natal nest and wait to encounter females that are entering or leaving a surrounding nest. Gynes are those females that leave the nest site after mating and enter a dormant state, and restart the cycle the following spring, while worker females, if they mate, remain in the natal nest.

In this species, there are foundress gynes and non-gynes. The gynes and non-gynes are distinct groups, as gynes mate, do not work, and enter diapause, while non-gynes work and do not diapause. There is evidence that male abundance may be the factor triggering this distinction early in life; if there is an abundance of males, a virgin female is more likely to encounter males and mate early shortly after emergence, and make a caste switch into being a gyne. If she is left unmated for two or three days, however, she will likely stay a non-gyne, even if she mates later on; no female who began acting as a worker was ever found to return the following season. "Halictus rubicundus" is the first bee species documented to have mixed broods containing both gynes and non-gynes, and it was previously thought that non-gynes and gynes were always produced in separate broods.Male abundance appears to have a major effect on deciding the social behavior within a population; the best predictor for a female's fate is the relative male abundance in proportion to virgin females on the first day a given virgin female emerges as an adult. Warmer temperatures during the first brood provisioning phase in the spring leads to a higher ratio of male to female offspring, and a significantly lower proportion of females are recruited as workers, reducing the overall level of sociality expressed in that population, ranging from above 75% in some years to below 45% in others, in the same location. Sex ratio is also affected by photoperiod at the time of egg production, with eggs laid on or near the summer solstice being almost exclusively male, so the earlier the season starts, the more female-biased the early brood phase will be, as in Kansas, where there are no males produced at all in the first brood, and there are three broods annually.There is evidence for greater genetic relatedness between two colonies with similar behavioral patterns, than between those of closer geographic distance but different social behaviors. This does not necessarily mean that social behavior is governed by certain genes, but it could be linked to certain genetic lineages that are more suited for certain environments. Empirical data from within a single population, however, indicates that females who do not remain as workers in their mother's nest are not more likely to have daughters that similarly depart. Although there is only limited research to date on the correlation between genetics, the environment, and social behavior, there is ample evidence that there are links between these three factors. The differences between the populations of "H. rubicundus" exhibiting solitary behavior, and those exhibiting eusocial behavior could be the result of environmental control of sociality, rather than having a purely genetic explanation.In environments with short breeding seasons, sociality is not expected because there is no benefit to acting as a worker in the absence of an opportunity to produce another brood that season, and no potential for kinship selection benefits. Populations in environments that allow for multiple broods exhibit eusocial behavior, and there are potential benefits to worker behavior in eusocial colonies, as workers are related to the foundress and the brood. Under theories of inclusive fitness, it is potentially beneficial for workers to help their mother produce a second brood if that brood is primarily female. However, "H. rubicundus" does not show female bias in the second brood, with values only ranging to a maximum of 40% female. Furthermore, the one study providing empirical data for "H. rubicundus" shows that a typical worker contributes to the production of 0.9 sisters and 0.8 brothers, far below the threshold for inclusive fitness effects to favor helping, but above the threshold at which their mother benefits directly; as such, this species provides evidence that kin selection effects would not apply to this species, and instead suggests that mothers manipulate some of their daughters into acting as workers because of direct gains to maternal fitness, even though these manipulated daughters have lower fitness than they could have had if they had been gynes.
orange-legged furrow bee  Geotagged,Halictus rubicundus,Orange-legged Furrow Bee,Spring,United States

Habitat

"H. rubicundus" has one of the widest natural distributions of any bee species, occurring throughout the temperate regions of the Holarctic region. It is believed that differences in climate across this vast range actually contribute to variation in their social behavior. Those living in more northern geographic locations or higher elevations are often more solitary in behavior than those in southern areas or lower elevations. This difference is widely studied, as it provides insight into the evolutionary transition from solitary to social behavior. Nests are haplometrotic, meaning that they are founded by single females. Social populations typically are found in warmer regions, such as Kansas, while solitary populations nest in cooler regions, such as Colorado, Scotland and Alaska. In intermediate regions, such as New York and southern Ontario, both social and solitary behavior can be found in different nests of the same population. The strictly solitary phenotype is expressed as a response to colder environments because the active season is not long enough to produce two broods.
Halictus rubicundus Doode Bemde, Belgium.  Belgium,Geotagged,Halictus rubicundus,Spring

Defense

Both solitary and eusocial types of the species typically excavate nest burrows in southward facing slopes in isolated areas, consisting of sand or soil. This slope maximizes the heat absorption from the sun, making the nest warmer. The nests with a favorable slope were thought to increase foraging efficiency of adults and development of larvae with a stable thermal environment.

Stones or areas of vegetation are usually found near nest entrances, likely because of the heating properties of these objects. For each offspring, a females constructs a small underground chamber, into which she deposits several loads of pollen mixed with nectar, which is then formed into a ball; a single egg is laid upon this pollen mass, and then the brood cell is sealed. The female repeats the process with other brood cells, going progressively deeper into the soil. A higher temperature increases the rate at which the larvae develop to maturity, as thermal regulation is important for the development of both the eggs and the larvae.

The nests can be up to 120 mm deep, and are constructed in a wide range of soil types. Because social nests produce more offspring than solitary nests, social nests will burrow further into the ground, as the second brood of the social population will extend the burrows downward. Females typically nest in dense aggregations, likely because the nesting females are relatives and demonstrate philopatric behavior.Dense nesting tendencies of "H. rubicundus" are most likely due to the following three factors:
# There is a limited amount of suitable substrate in which the bees can build their nests, so they must build many nests packed tightly together without compromising the structural integrity of the nest.
# As mentioned earlier, philopatry is an important factor in maintaining an aggregation. The search for a new nesting site requires a lot of resources, so females will likely limit their dispersal and stay near their natal nest sites.
# Hymenopteran and dipteran species may attack the ground nest of "H. rubicundus". Although it would seem that aggregation of nesting would increase the mortality due to parasitism as they would be more conspicuous, it is likely that there is a dilution effect that reduce mortality by parasitism.

References:

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Taxonomy
KingdomAnimalia
DivisionArthropoda
ClassInsecta
OrderHymenoptera
FamilyHalictidae
GenusHalictus
SpeciesH. rubicundus