Patterns of provisioning and iteroparity in a solitary halictine bee,Lasioglossum (Evylaeus) fratellum (Perez), with notes onL. (E.) calceatum (Scop.) andL. (E.) villosulum (K.)

Summary On Dartmoor, UK the temperate halictine beeLasioglossum (Evylaeus) fratellum is solitary and univoltine. A significant proportion of individually marked foundresses reproduce during two different seasons (iteroparity). This could represent a form of risk-spreading in environments where conditions are harsh and unpredictable. Perhaps associated with iteroparity, foundresses put in relatively low reproductive effort, often failing to provision their nests on suitable days, despite the small number of days available on Dartmoor. Foundresses stopped provisioning asynchronously, then remained in their nests until well after offspring emergence. There was a small proportion of digynous nests, in which nest-sharing appeared to be temporary.L. (E.) calceatum had a similar life-cycle on Dartmoor.L. villosulum was also solitary, and was able to provision its nests under less favourable weather conditions than the other two species. Information is also provided on nest productivity andSphecodes parasites.     

New records for the bee fauna of Iran (Hymenoptera: Apoidea)

In a survery of the bee fauna of Horand forests in East Azerbaijan province of Iran during 2008 and 2009, 46 species belonging to the families Anthophoridae, Halictidae and Megachilidae were identified. Eight species are new to the fauna of Iran: Evylaeus albipes (Fabricius, 1781), E. corvinus (Morawitz, 1878), E. israelensis (Ebmer, 1974), Seladonia desertorum (Morawitz, 1876), Heriades crenulatus Nylander, 1856, Hoplitis anthocopoides (Schenck, 1853), H. manicata (Morice, 1901) and H. rufohirta (Latreille, 1811).     

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.     

A new species of Psidium L. (Myrtaceae) from southern Brazil

Rewardless kettle‐trap flowers Cypripedium yunnanense and C. flavum were watched for pollinators during 73 and 101 man‐hours, respectively, in north‐west Yunnan at 3490–3590 m a.s.l. They differ from typical Cypripedium, such as C. calceolus, in having a broad infolded flap of the lip extending all around the entrance of the pouch (instead of being restricted to the vicinity of the staminode) and in the flap not being slippery. Cypripedium yunnanense is pollinated by Lasioglossum zonulum euronotum (Halictidae), and C. flavum is pollinated by Andrena orchidea and Andrena sp. (Andrenidae, two of nine new hymenopterans discovered at the sites). The bees do not inadvertently fall into the trap by slipping (as often occurs in other slipper orchids), but enter it by crawling down the flap in full control of their movements. No natural hybrids between the two orchids are known, although they occur in close‐by or mixed stands, are co‐flowering and size compatible with regard to their pollinators, and produce fruits following manual cross‐pollination in situ. Analyses of the (non‐Cypripedium) pollen carried indicate that: (1) the two andrenids are probably oligolectic; (2) the andrenids and the halictid do not share the same flower species; and (3) the halictid is polylectic. Points (1) and (2) are probable reasons for the lack of hybrids. The other reason why Lasioglossum zonulum euronotum does not visit C. flavum despite being polylectic may be the flower's odour; cases of discrimination of closely related flowers by polylectic Lasioglossum have been reported elsewhere. Blow flies Calliphora vomitoria and Calliphora pattoni (Calliphoridae) also enter the orchids, some smearing themselves with pollen, yet they are not pollinators. They are too large to leave by the exit and die imprisoned. However, they may be accidental pollinators of the rather larger C. tibeticum present at the sites. Such accidental pollinators probably play an important role in the evolution of new pollination syndromes. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 156 , 51–64.     

Colony social organization of <Emphasis Type="Italic">Lasioglossum malachurum</Emphasis> Kirby (Hymenoptera,Halictidae) in southern Greece

Summary We studied the nesting and social biology of two aggregations of the obligately eusocial halictine bee Lasioglossum malachurum at Agios Nikolaos Monemvasias (ANM) in southern Greece. Observations and nest excavations carried out from May to June 2000, revealed social and demographic variation between aggregations and years at ANM, as well as notable differences between these and other European populations. In southern Greece, the colony cycle includes multiple broods: the first two broods comprise only workers, whereas the third brood comprises workers, males, and gynes. Although pleometrosis is unknown in other populations, in the ANM region, as many as 10% of nests have more than one foundress. Newly emerged workers and gynes exhibit non-overlapping size distributions, but a few queens are worker-sized, indicating that workers occasionally overwinter and become foundresses. Although the vast majority of workers are unmated and most exhibit no ovarian development, an increase in worker ovarian development at the time of male production suggests that many males may develop from worker-laid eggs. Worker reproduction seems to be inhibited by the presence of queens, and annual variation in queen mortality may underlie annual variation in worker ovarian development. Across Europe, the major demographic and social differences among L. malachurum populations are in the number of worker broods and the extent of worker ovarian development. This contrasts with the results of a principal components analysis of social traits among 15 social L. (Evylaeus) populations, which shows that interspecific social variation is defined by the proportion of males in the early brood, the proportion of workers mated, queen-worker size dimorphism, gyne overwintering locale, and the proportion of workers with developed ovaries.Received 17 June 2002; revised 16 January 2002; accepted 27 January 2003.     

A simple floral fragrance and unusual osmophore structure in Cyclopogon elatus (Orchidaceae)

We studied gland morphology, anatomy and the chemical composition of the floral fragrance in the sweat bee-pollinated orchid Cyclopogon elatus . This is apparently the first such analysis for any Cyclopogon species, and one of very few studies in which both odour and osmophore are characterised in a nectar-rewarding orchid. Structures responsible for floral scent production were localised with neutral red staining and histochemical assays for lipids and starch. Their morphology and anatomy were studied with scanning electron microscopy and light microscopy thin sections, respectively. Fragrance samples were collected using SPME fibres and analysed with GC-MS. Anatomical evidence suggests that two parallel oval-shaped patches of unicellular trichomes on the abaxial surface of the labellum are osmophores. These are rich in stored lipids, while the parenchyma surrounding the vascular bundles contains starch. Only freshly opened flowers produced odours, while buds and withered flowers lacked scent. The chemical composition of the odour was dominated (>99.8%) by a single compound, trans-4,8-dimethyl-nona-1,3,7-triene (DMNT). Gland anatomy and position on the outside of the perianth are unusual for scent glands in general. The presence of DMNT, a nearly ubiquitous compound in herbivore-induced vegetative emissions and one of the major floral volatiles of Yucca , is not surprising in view of hypotheses on the evolutionary origin of flower scents, suggesting that wound volatiles are utilised as kairomonal attractants by florivores whose activities result in pollination.     

Bees provide pollination service to Campsis radicans (Bignoniaceae), a primarily ornithophilous trumpet flowering vine

1. Pollination syndromes refer to stereotyped floral characteristics (flower colour, shape, etc.) that are associated with a functional group of pollinators (bee, bird, etc.).
2. The trumpet creeper Campsis radicans, endemic to the southeast and mid‐west United States, has been assigned to the hummingbird‐pollination syndrome, due mainly to its red, trumpet‐shaped flowers.
3. Previous studies demonstrated that the ruby‐throated hummingbird Archilochus colubris is C. radicans' primary pollinator, but anecdotal data suggest various bee species may provide pollination service when hummingbirds are absent.
4. This study characterised C. radicans nectar volume and concentration by time of day. Nectar volume was suitable for hummingbirds, but concentration was higher than typical hummingbird‐pollinated plants (～20% w/w); at ～30% w/w, it approached the concentration expected in bee‐pollinated plants (～50% w/w). We also found substantial amounts of nectar at night.
5. Two C. radicans populations received virtually no hummingbird visits, but the number of bees were markedly higher than in the populations previously described. Interestingly, there were no night‐time visitors despite the large quantity of nocturnal nectar.
6. Based on previously published pollen delivery per visit by various species, this study estimated that cumulative deposition by bees routinely reached pollen deposition thresholds for setting fruit in C. radicans. They are, unequivocally, the predominant pollinators in these populations, thus providing pollination service in the absence of hummingbirds.
7. These results highlight C. radicans as a food source for native bees and add to the understanding of how floral phenotypes can facilitate pollination by disparate functional groups.

     

Queen Dominance May Reduce Worker Mushroom Body Size in a Social Bee

The mushroom body (MB) is an area of the insect brain involved in learning, memory, and sensory integration. Here, we used the sweat bee Megalopta genalis (Halictidae) to test for differences between queens and workers in the volume of the MB calyces. We used confocal microscopy to measure the volume of the whole brain, MB calyces, optic lobes, and antennal lobes of queens and workers. Queens had larger brains, larger MB calyces, and a larger MB calyces:whole brain ratio than workers, suggesting an effect of social dominance in brain development. This could result from social interactions leading to smaller worker MBs, or larger queen MBs. It could also result from other factors, such as differences in age or sensory experience. To test these explanations, we next compared queens and workers to other groups. We compared newly emerged bees, bees reared in isolation for 10 days, bees initiating new observation nests, and bees initiating new natural nests collected from the field to queens and workers. Queens did not differ from these other groups. We suggest that the effects of queen dominance over workers, rather than differences in age, experience, or reproductive status, are responsible for the queen–worker differences we observed. Worker MB development may be affected by queen aggression directly and/or manipulation of larval nutrition, which is provisioned by the queen. We found no consistent differences in the size of antennal lobes or optic lobes associated with differences in age, experience, reproductive status, or social caste.     

Nest site preference and success in a gregarious, ground-nesting bee Dieunomia triangulifera

1. The characteristics of preferred nest sites of the solitary bee Dieunomia triangulifera, which nests gregariously in alluvial soil, were investigated. Nest presence was used as an indication of preference. In those cases where nests were more than a few days old, therefore, this study also investigated nest success. 2. Independent variables tested were soil surface moisture, presence of nesting conspecifics, smooth vs. irregular soil surface, distance to visual landmarks, percentage of vegetation cover, soil compaction, vehicular traffic, soil surface temperature, and light intensity. 3. Bees preferred to nest in moist, compact soil with an irregular surface. More bees nested near visual landmarks and in places with little or no vegetation. They preferred nesting in areas with warmer soil surface temperatures and brighter illumination. The presence of nesting conspecifics did not influence nesting decisions. Vehicular traffic also seemed to have no impact on nest initiation but did seem to have a negative impact on nest success. 4. Although it might seem that ground-nesting bees should not be limited by nesting sites, relatively little of the study area met all their apparent criteria. This might account, in part, for gregarious nesting in this species.     

Pollen use by Megalopta sweat bees in relation to resource availability in a tropical forest

1. Spatial and temporal availability of pollen helps shape bee foraging behaviour and productivity, which has been studied in great detail at the landscape level, but never in a diverse tropical forest. 2. To study the effect of spatio‐temporal variation in resource distribution on pollen use and productivity, we identified pollen from spatially explicit nest collections of two generalist sweat bees, Megalopta genalis Meade‐Waldo and M. centralis Friese, from Barro Colorado Island, Panama, a 50‐ha forest dynamics plot during the 2007 dry and early wet seasons. Pollen from nests collected in 1998–1999 without spatial information was also identified. 3. Bees used pollen of at least 64 species; many of these occurred in only one collection. The 2007 collections contained pollen of 35 different species, but were dominated by five species, especially Hura crepitans L. and Pseudobombax septenatum (Jacq.) Dugand. 4. Temporal availability, but not distance from nest, influenced flower use at a 50‐ha scale. 5. Body size was not associated with minimum flight distance as inferred from pollen collections. 6. Nest productivity and pollen diversity decreased from the dry to wet seasons, mirroring community‐level availability of floral resources. 7. Results suggest that on a scale of 50 ha, bees are choosing certain host plant species regardless of distance from the nest, but adjusting foraging behaviour opportunistically based on the temporal availability of host flowers.