Escalation of Aggressive Interactions During Staged Encounters in Halictus ligatus Say (Hymenoptera: Halictidae), with a Comparison of Circle Tube Behaviors with Other Halictine Species'

Circle tube experiments on the primitively eusocial bee, Halictus ligatus, were performed for a variety of combinations of caste and size. Push, Lunge, and Back without reverse behaviors enabled us to determine the dominant individual in most comparisons. Behavioral differences were readily detected within the first 15 min except for different-size forager–forager and same-size foundress–foundress pairs, for which 30 min of observations was required. In same-size forager–forager pairs, no differences in behaviors between individuals were detected even after 90 min. In extended observations, decreases in the frequency of the mild dominant behaviors were accompanied by a switch to the highly aggressive mandibular hold on the neck, particularly in different-size foundress–foundress and gyne–gyne pairs. Three workers were killed by their own queen as a result of this escalation of aggression. We discuss caste-based differences in the circle tube setting in terms of behaviors expected under more normal conditions and compare our data with published results from other species.     

Biology of Nomioides variegatus (Olivier) (Hymenoptera: Halictidae)

The nesting biology, life history and pollen foraging of the minute Nomioides variegatus (Olivier) is described and illustrated. All Nomioides biological studies are reviewed. Nesting and foraging were observed over two years in a sandy natural area in the Rhône River delta region of southern France. Nest and cell structure was obtained from soil blocks removed from the nesting area and examined in the laboratory. Females, which were on average only 4.2 mm long, nested solitarily in loose aggregations in areas free of vegetation. Cells were placed from 6 to 12 cm deep, each terminating a lateral burrow off the main burrow. Cell walls were lined with a water proof wax-like lining. The pollen-nectar provision was a flattened sphere. The posterior end of the egg was embedded on the dorsal surface of the provision. Larval and pupal development was rapid, proceeding to adults by August, the over-wintering stage. Pollen foraging patterns were analyzed from both pollen provisions and fecal material for different nests (3) and cells (8). Nomioides variegatus is polylectic, but individuals bees exhibited a high degree of foraging consistency for the provisioning of single cells. Eleven different pollen types representing 10 plant families were found. In 1996, Ecballium elaterium (Cucurbitaceae) was the dominant pollen present in all samples but it was absent in 1997. Tamarix gallica (Tamaricaeae) was the dominant pollen type in 1997 and absent in 1996. A third pollen, Centaurium (Gentianaceae) was present in both years and represented 70% of some samples.     

Novel antimicrobial peptides from the venom of the eusocial bee Halictus sexcinctus (Hymenoptera: Halictidae) and their analogs

Two novel antimicrobial peptides, named halictines, were isolated from the venom of the eusocial bee Halictus sexcinctus. Their primary sequences were established by ESI-QTOF mass spectrometry, Edman degradation and enzymatic digestion as Gly-Met-Trp-Ser-Lys-Ile-Leu-Gly-His-Leu-Ile-Arg-NH₂ (HAL-1), and Gly-Lys-Trp-Met-Ser-Leu-Leu-Lys–His-Ile-Leu-Lys-NH₂ (HAL-2). Both peptides exhibited potent antimicrobial activity against Gram-positive and Gram-negative bacteria but also noticeable hemolytic activity. The CD spectra of HAL-1 and HAL-2 measured in the presence of trifluoroethanol or SDS showed ability to form an amphipathic α-helical secondary structure in an anisotropic environment such as bacterial cell membrane. NMR spectra of HAL-1 and HAL-2 measured in trifluoroethanol/water confirmed formation of helical conformation in both peptides with a slightly higher helical propensity in HAL-1. Altogether, we prepared 51 of HAL-1 and HAL-2 analogs to study the effect of such structural parameters as cationicity, hydrophobicity, α-helicity, amphipathicity, and truncation on antimicrobial and hemolytic activities. The potentially most promising analogs in both series are those with increased net positive charge, in which the suitable amino acid residues were replaced by Lys. This improvement basically relates to the increase of antimicrobial activity against pathogenic Pseudomonas aeruginosa and to the mitigation of hemolytic activity.     

Genetic differentiation across a behavioural boundary in a primitively eusocial bee, <Emphasis Type=Italic>Halictus poeyi</Emphasis> Lepeletier (Hymenoptera,Halictidae)

Summary. In Florida, the primitively eusocial bee, Halictus poeyi Lepeletier exhibits two different colony cycles: populations in northern and central Florida are univoltine with an annually brooded colony cycle, while populations in southern Florida, including the Florida Keys, are multivoltine with a continuously brooded colony cycle. In this study, we test the hypothesis of reduced gene flow between the colony types by comparing levels of genetic differentiation among populations having similar colony phenologies with that among populations having different colony phenologies. We use allozyme markers to estimate F_ST, a robust measure of genetic differentiation. We found that genetic differentiation is not significantly higher between populations having different colony phenologies than between populations having similar colony phenologies. Environmental conditions thus may play an important role in influencing the expression of the alternative colony types of H. poeyi populations in Florida.     

Flagellar Sensilla of Sphecodes Bees (Hymenoptera, Halictidae)

The antenna of Sphecodes bees were investigated as regards the type and distribution of the sensilla. Eleven species originating from Sweden were used. Totally 325 specimens were studied. The distribution of sensilla placodea and sensilla trichodea on the antennal segments were studied in the light stereomicroscope. One to three antennae per species were also examined by SEM. The following types of sensilla were found: s. placodea; pit organs; s. campaniformia; s. basiconica; s. trichodea A, B and CD; and setae. The distribution of sensilla, especially s. placodea and s. trichodea A, was found to be species-specific in the male sex and their diagnostic value in taxonomy is stressed. In the female sex no specific characteristics were found, although two groups could be distinguished.     

Phylogeny of the bee genus Agapostemon (Hymenoptera: Halictidae)

Abstract. A phylogeny for genus Agapostemon (Hymenoptera: Halictidae) is reconstructed from morphological characters, using all species, with four representatives of Agapostemonini as outgroup taxa. Parsimony analysis using 150 unordered characters resulted in eighteen equally parsimonious trees, a strict consensus of which is highly resolved for Agapostemon. Based on this analysis, Agapostemonoides Roberts & Brooks is returned to generic status, and a new subgenus is described: Notagapostemon, which includes the rhopalocerus, heterurus, atrocaeruleus, erebus, kohliellus, nasutus and intermedius groups of Moure & Hurd. Species groups are proposed for Notagapostemon and revised in A. (Agapostemon). Agapostemon cockerelli Crawford is synonymized with A. obliquus (Provancher), A. epichryseus (Morelos) with A. leunculus Vachal, A. inca Roberts with A. heterurus Cockerell, A. hispaniolicus Roberts female with A. centratus (Vachal) and A. hispaniolicus Roberts male with A. alayoi Roberts. Optimization of known behaviours suggests communal ancestry for the genus and infers the prevalence of this behaviour in Agapostemon. Optimization of geographical range suggests a Central American or Caribbean origin of Agapostemon, with one invasion of North America and multiple invasions of South America and the Caribbean. One invasion of the Caribbean suggests arrival from North America via Florida.     

Mating Behavior in Halictine Bees (Hymenoptera: Halictidae)

Studied two types of mate-orientation behavior in ♂♂ of the sweat bee, Lasioglossum rohweri: microterritoriality and patrolling. Observations were made in both the laboratory and the field. These ♂♂ behave uniquely for Hymenoptera in that 2–5 of them establish microterritories immediately around the same nest entrance. Some ♂♂ are exclusively patrollers, flying about flowers and nest sites. Rendezvous places (locations where animals are likely to find mates) in bees are: flowers, nesting sites, vegetative parts of plants, nest entrances, air, and nests. Territoriality in male bees may have arisen independently in 7 of the 9 families of bees.     

Colony dynamics in a primitively eusocial halictine beeLasioglossum (Dialictus) zephyrum (Hymenoptera: Halictidae)

Summary Proximate control of colony dynamics was studied in the primitively eusocial halictine beeLasioglossum (Dialictus) zephyrum using allozyme markers. The results indicate that workers produce on average 15% of the male brood (range=0–50%) in small laboratory colonies made up of unrelated, single-generation, uninseminated females. This proportion is not influenced by colony size, but is influenced by the relative size of the queen. Large queens are more successful in dominating their workers than are small queens, the queen being defined as the female that is the mother of most of the brood produced in the colony. Older and larger females tend to become queens. Thus, while small differences in age (up to 4 days) influence which female becomes a queen, her ability to control her workers is primarily influenced by her relative size. The proportion of reproduction that is co-opted by the queen is negatively correlated with colony reproductivity (the number of males/day/female). Colony reproductivity is also negatively correlated with the standard deviation in size among females.     

Lasioglossum (Dialictus) tenax (Sandhouse) (Hymenoptera: Halictidae) as a solitary sweat bee

Summary Nine nests ofLasioglossum (Dialictus) tenax were excavated near Calgary, Alberta, Canada over a time period encompassing the entire brood production period in 1988. Each nest contained a maximum of one active adult female, nest productivity peaked in mid July, protandry was noted and no significant size difference between foundresses and the earlier emerging females was detected. These data suggest that this species is solitary. These results are compared with data for the sympatrically nesting eusocial speciesL. (D.) laevissimum.     

The population genetics of a solitary oligolectic sweat bee, Lasioglossum (Sphecodogastra) oenotherae (Hymenoptera: Halictidae)

Strong evidence exists for global declines in pollinator populations. Data on the population genetics of solitary bees, especially diet specialists, are generally lacking. We studied the population genetics of the oligolectic bee Lasioglossum oenotherae, a specialist on the pollen of evening primrose (Onagraceae), by genotyping 455 females from 15 populations across the bee's North American range at six hyper-variable microsatellite loci. We found significant levels of genetic differentiation between populations, even at small geographic scales, as well as significant patterns of isolation by distance. However, using multilocus genotype assignment tests, we detected 11 first-generation migrants indicating that L. oenotherae's sub-populations are experiencing ongoing gene flow. Southern populations of L. oenotherae were significantly more likely to deviate from Hardy-Weinberg equilibrium and from genotypic equilibrium, suggesting regional differences in gene flow and/or drift and inbreeding. Short-term N(e) estimated using temporal changes in allele frequencies in several populations ranged from approximately 223 to 960. We discuss our findings in terms of the conservation genetics of specialist pollinators, a group of considerable ecological importance.     

A new species of Microsphecodes from Jamaica (Hymenoptera, Halictidae)

A new species of the cleptoparasitic bee genus Microsphecodes Eickwort and Stage (Halictinae: Halictini) is described and figured from a male and female collected in Jamaica. Microsphecodes xaymacensis Engel, sp. n., is distinguished from its congeners on the basis of integumental coloration and sculpturing, and form of the male pygidial plate and genitalia.     

Proventricular structure in the bee tribe Augochlorini (Hymenoptera: Halictidae)

Characters of the digestive tract have received little attention in modern phylogenetic analyses regarding relationships among bees, in part because studies on the internal morphology of bees generally concentrate on physiological and behavioural aspects. This paper presents a comparative study of the proventricular structure, analysed with scanning electronic microscopy, in bees of the tribe Augochlorini. Eleven species of Augochlorini were analysed as the ingroup, versus one each of Halictini and Caenohalictini, and two of Crabronidae as outgroups. The presence of a long columnar proventricular fold is an apomorphy for Augochlorini, whereas a proventricular fold with a keel-shaped structure at the moving lip level is an apomorphy for Augochlorina. Together these data corroborate the monophyly of Augochlorini and Augochlorina, respectively.     

Seladonia (Pachyceble) henanensis sp. n. (Hymenoptera,Halictidae) from China

Seladonia (Pachyceble) henanensis sp. n., is described from Henan Province, the eastern-central part of China. This species is separated from its allied species by a combination of the following morphological characters: head broad in female, inner hind tibial spur of female with 7–8 slender teeth, T1 basolaterally with appressed hair tuft in both sexes, and genitalia with long and large lower gonostylus in male. Important taxonomic characters are illustrated with photographs, scanning electron micrographs, and line drawings.     

The biology of the primitively eusocial Augochloropsis iris (Schrottky, 1902) (Hymenoptera, Halictidae)

Summary: This work investigated Augochloropsis iris, its annual colony cycle, brood size and survival rate, caste differentiation, and sex ratio, and is the first detailed account of a clearly eusocial species of this genus. The population studied is located in the Campos do Jordão State Park, São Paulo, Brazil. The annual colony cycle extends from August to March and consists of three phases of cell provisioning separated by two phases of inactivity, and followed by an emergence of future queens and males. Provisioning during the first phase is carried primarily out by solitary females. The daughters, after emerging from the cells, remain in the natal nests, carrying out foraging activities, while the mother engages in reproduction. New nests are initiated during each of the provisioning phases by solitary females, principally by females from the second-phase brood which, soon after emerging from the cells, leave their natal nests to found their own nests, which they provision during the third phase. The females resulting from the third-phase brood in general mate and excavate their own nests, in which they diapause, with provisioning delayed until the following August. On average, the queens are significantly larger (5%) than the workers. In general, the workers do not have developed ovaries, but all are mated. Kin selection can be accepted as the selective force responsible for worker behavior of A. iris in eusocial colonies when the queen has mated once and semisocial colonies if the queen mated only once. The percentage of males produced in the first, second and third broods and in the brood of new nests founded by solitary females active in the second and third phases was: 20.7%, 22.2%, 13.3% and 0.0% respectively. The resultant sex ratio of the third brood suggests that the third-phase workers of eusocial nests are at least in partial control of their colony's sex ratios, in cases where the queens mated only once.     

A new species of Parapygmephorus Cross, 1965 (Acari; Heterostigmatina; Neopygmephoridae) phoretic on Halictus quadricinctus (Fabricius, 1776) (Hym.; Halictidae) from Iran

A new species of the genus Parapygmephorus Cross, 1965 (Acari: Heterostigmatina, Neopygmephoridae) is described from Northeastern Iran. A phoretic adult female of Parapygmephorus khorasanicus Hajiqanbar and Khaustov sp. n. was discovered clasping on hairs on the ventral body surface of Halictus quadricinctus (Fabricius, 1776) (Hymenoptera; Halictidae). It is the fifth representative among the known species of the genus Parapygmephorus in the world. Differentiation of new species from other species of the genus is discussed, and a key to known world species is provided.     

Alternative Reproductive Strategies of a Gregarious Ground-Nesting Bee, Dieunomia triangulifera (Hymenoptera: Halictidae)

I studied reproductive behavior of females of the gregarious ground-nesting bee Dieunomia triangulifera (Halictidae). During peak bloom of the host plant, Helianthus annuus, some females consistently brought pollen to one nest (provisioning bees), whereas others visited many nests without taking pollen to any (searching bees). Searching bees were more likely to have two or more developed oocytes and crops full of pollen. The ingested pollen probably provided protein for egg production. The differing behavior of provisioning and searching bees combined with contrasting internal morphology, indicated that these two sets of behaviors were alternative reproductive strategies. Three possible explanations for the searching bees' behavior included: usurpation, floating, or intraspecific cleptoparasitism. Each of these is evaluated as a possible function of searching behavior. Given the evidence I conclude that intraspecific cleptoparasitism is the most likely explanation.