Miocene honey bees from the Randeck Maar of southwestern Germany (Hymenoptera, Apidae)

The Miocene Randeck Maar (southwestern Germany) is one of the only sites with abundant material of fossil honey bees. The fauna has been the focus of much scrutiny by early authors who recognized multiple species or subspecies within the fauna. The history of work on the Randeck Maar is briefly reviewed and these fossils placed into context with other Tertiary and living species of the genus Apis Linnaeus (Apinae: Apini). Previously unrecorded specimens from Randeck Maar were compared with earlier series in an attempt to evaluate the observed variation. A morphometric analysis of forewing venation angles across representative Recent and Tertiary species of Apis as well as various non-Apini controls was undertaken to evaluate the distribution of variation in fossil honey bees. The resulting dendrogram shows considerable variation concerning the wing venation of Miocene Apini, but intergradation of other morphological characters reveals no clear pattern of separate species. This suggests that a single, highly variable species was present in Europe during the Miocene. The pattern also supports the notion that the multiple species and subspecies proposed by earlier authors for the Randeck Maar honey bee fauna are not valid, and all are accordingly recognized as Apis armbrusteri Zeuner.     

Influences on the density and dispersion of bumble bee nests (Hymenoptera: Apidae)

To determine some of the influences on nesting densities of bumble bees I examined the dispersion and occupancy of 35 nests in an old field on Amherst Island, Ontario, Canada and 39 nests found by Cumber (1953) in England. Densities up to 1 nest per 200 m² were observed. Overall, Cumber's nests were randomly dispersed, but nests on the ground surface were aggregated. Nests of surface-nesting species were consequently more aggregated than expected at random, whereas surface-nesting and underground-nesting species seldom nested near one another. This distribution of nests probably reflects the nesting habits of the rodents that originally constructed the nests, rather than interactions between bees. On Amherst Island, abnormally wet spring weather apparently hampered normal colony development, particularly of underground-nesting bees based on a low frequency of underground nests, scarcity of workers of two underground-nesting species compared with the relative abundance of spring queens, and delayed appearance of workers of all species relative to the previous year. The nests of two common species were randomly dispersed, but those of a third species were regularly distributed, suggesting that intraspecific interactions may limit nesting density for this species.     

Effect of bumble bee (Hymenoptera: Apidae) pollination intensity on the quality of greenhouse tomatoes

Laboratory studies were conducted to assess tomato, Lycopersicon esculentum Mill. (Solanaceae), quality in relation to the level of buzz-pollination by bumble bees. Studies were conducted in commercial tomato greenhouses in the Leamington, Ontario, area to categorize bruising of tomato anther cones by bumble bees into five levels of bruising. The number of pollen grains per stigma was determined for each bruising level, and the bruising level was found to be a good predictor of stigmatic pollen load. Experimental flowers were pollinated by bumble bees and assigned to bruising levels based on the degree of anther cone discoloration. Fruit set, tomato weight, minimum diameter, the number of days until ripe, roundness, weight, percentage sugars, and number of seeds were assessed and compared among bruising level. Fruit set in flowers receiving no pollination visits was 30.2%, whereas, 83.3, 84.4, 81.2, and 100% of the flowers set fruit in bruising levels 1, 2, 3, and 4, respectively. Minimum diameter, number of seeds, and tomato weight all increased from no bruising to different levels of bruising. There was no increase in weight or diameter above a bruising level of 1, and no increase in the number of seeds per fruit after a bruising level of 2. We found that pollination of tomato flowers greater than a bruising level of 2 (corresponding to approximately one to two bee visits) did not result in a significant increase in quality.     

Allozyme variation in bumble bees (Hymenoptera: Apidae)

Allozyme variation at an average of 37.3 loci was assessed in queens of 16 Bombus and 2 Psithyrus bumble bee species from North America. The mean expected heterozygosity (H) for the Bombus species was 0.008 +/- 0.006 (95% confidence limits) and that for the Psithyrus was 0.007 +/- 0.007. These levels are significantly lower than found in other Hymenoptera but are comparable to those found in previous studies of bumble bees based on far fewer loci. Neutral mutation and random genetic drift can account for the observed variation, but this implies a very small effective population size for species of bumble bees.     

Frugivory by a stingless bee (Hymenoptera: Apidae)

Frugivory is not frequent among bees. Although stingless bees visit aged fruits for pulp, the use of fresh fruits is recorded only for Trigona hypogea Silvestri, a species that does not visit flowers. Here we report the occurrence of frugivory in Trigona amazonensis (Ducke), a flower-visiting stingless bee.     

Geographical patterns of genetic divergence in the widespread Mesoamerican bumble bee Bombus ephippiatus (Hymenoptera: Apidae)

Bumble bees (Bombus Latreille) are an important group of social insects, well recognized throughout northern temperate regions as important pollinators of wild and agricultural plants. Little is known about the biology of this group in southern portions of the Americas, especially in Mesoamerica, a region of geological and ecological complexity from Mexico through Central America. One ubiquitous Mesoamerican species, Bombus ephippiatus, is enigmatic. Like many other Bombus, this species is homogeneous in body structure yet exhibits striking intraspecific color pattern polymorphism across its range, leading to uncertainty about its genealogical boundaries. It has been grouped taxonomically with B. wilmattae, a species narrowly restricted to southern Mexico and northern Guatamala. Furthermore, the relationships between these two taxa and a third species, B. impatiens, found only in America north of Mexico, have been controversial. Our phylogenetic analysis of DNA sequences from mitochondrial COI and nuclear PEPCK and CAD resolves the phylogeny of these three taxa as (B. impatiens, (B. ephippiatus, B. wilmattae)). Additional data from eight nuclear microsatellite markers reveal complex patterns of genetic divergence and isolation among populations of B. ephippiatus across its extensive geographic range, providing evidence for multiple independent evolutionary lineages. These lineages correspond not only to geographic and habitat variation across their range, but also to distinct color pattern groups present in the species. Knowledge of the phylogeny and genetic divergence of the B. ephippiatus group will provide a framework for understanding evolutionary and ecological origins of color pattern polymorphism in bumble bees, as well as providing insight into geographical factors enhancing speciation in Mesoamerica.     

Landscape heterogeneity predicts gene flow in a widespread polymorphic bumble bee, Bombus bifarius (Hymenoptera: Apidae)

Bombus bifarius is a widespread bumble bee that occurs in montane regions of western North America. This species has several major color pattern polymorphisms and shows evidence of genetic structuring among regional populations, and the taxonomic status of regional populations has repeatedly been debated. We test whether observed structure is evidence for discrete gene flow barriers that might indicate isolation or instead reflects clinal variation associated with spatially limited dispersal in a complex landscape. We first consider color pattern variation and identify geographical patterns of B. bifarius color variation using cluster analysis. We then use climate data and a comprehensive set of B. bifarius natural history records with an existing genetic data set to model the distribution of environmentally suitable habitat in western North America and predict pathways of potential gene flow using circuit theory. Resistance distances among populations that incorporate environmental suitability information predict patterns of genetic structure much better than geographic distance or Bayesian clustering alone. Results suggest that there may not be barriers to gene flow warranting further taxonomic considerations, but rather that the arrangement of suitable habitat at broad scales limits dispersal sufficiently to explain observed levels of population differentiation in B. bifarius.     

Commercial bumble bee Bombus impatiens (Hymenoptera: Apidae) as a pollinator in lowbush blueberry (Ericale: Ericaceae) fields

Here, we evaluate the potential of the bumble bee Bombus impatiens Cresson, obtained from commercial colonies, as a pollen vector for lowbush blueberry, Vaccinium augustifolium Aiton. We wanted to gain insight into the relationships between pollination by introduced bumble bees, the categories of seeds produced, and the weight and the maturity of the blueberries. The effect of B. impatiens foraging in blueberry stands was measured quantitatively through fruit set and seed set analysis. We created a density gradient of B. impatiens by clustering 72 small hives at the southern extremity of blueberry fields located in Girardville (49 degrees 00' N, 72 degrees 33' W), Quebec, Canada. Observers recorded plant and insect data in 52 plots of 1 by 10 m, distributed at distances ranging from 25 to 1,500 m from the hives. From these data, we evaluated the fruit set rate, the weight and maturity of the berries, and the number of seed structures per berry, including true seeds of large, medium, and small size, pseudo-seeds, and ovules. Positive correlations were found between the density of B. impatiens and fruit set as well as the number of large seeds per berry. Large seeds influenced the weight and maturity of berries. B. impatiens acted as a "near-nest central forager" and increased fruit set and seed production up to 100 and 150 m respectively, from the hives.     

Analysis of the labial gland secretions of the male bumble bee Bombus perplexus Cresson (Hymenoptera: Apidae) from North America

The labial gland secretions from males of the bumble bee Bombus (Pyrobombus) perplexus Cresson were analysed by gas chromatography/mass spectrometry (GC/MS) in the electron impact and positive ion chemical ionization mode. The major compound of the complex mixture of alkenols, alkenals, fatty acids, hydrocarbons, wax type esters and steroids is 3,7,11,15-tetramethyl-2,6,10-hexadecatrien-1-ol (geranylcitronellol), considerable amounts of hexadecan-1-ol and Z-9-hexadecen-1-ol were also found. All alcohols were present as esters of the detected acids. In older samples both the acids and the alcohols sometimes could not be detected in the GC; therefore, the possibility to check the detected acid-alcohol pattern by interpreting the wax type ester peaks is very instructive. Moreover, the labial gland contains a rich mixture of mono- and di-unsaturated straight chain hydrocarbons. The similarity in composition of the labial glands of the North American B. (Pyrobombus) perplexus with the Eurasian species B. (Pyrobombus) hypnorum corroborates the assumption that the two species are conspecific. The likely supposition that the hydrocarbons could play an essential role in the chemical communication in bumble bees is discussed.     

A new species of the cleptoparasitic bee genus Thyreus from northern Yemen and southwestern Saudi Arabia (Hymenoptera,Apidae)

A new species of cleptoparasitic bee of the genus Thyreus Panzer (Apinae: Melectini) is described and figured from northern Yemen and southwestern Saudi Arabia. Thyreus shebicus Engel, sp. n. is a relatively small species superficially similar to the widespread and polytypic species T. ramosus (Lepeletier de Saint Fargeau) and T. ramosellus (Cockerell) but more closely allied to various African forms on the basis of the male genitalia. The species is distinguished from its congeners on the basis of coloration pattern, male hind leg structure, and particularly male terminalia.     

Bombus folsomi and the origin of Philippine bumble bees (Hymenoptera: Apidae)

Abstract The type female of Bombus folsomi (Frison) is redescribed and synomymized with B.ephippiatus Say. It is concluded that the putative type locality of B.folsomi , Mt Kinabalu in Borneo, is in error and that the genus appears to be absent from Borneo. This lends support to the hypothesis that bumble bees immigrated to the Philippines by an unusual northern route through Taiwan. More rigorous testing of this idea will require further cladistic analysis of the genus Bombus .     

Queen-worker conflict and social parasitism in bumble bees (Hymenoptera: Apidae)

Psithyrus ashtoni (Hymenoptera: Apidae) is an obligate, workerless bumble, bee social parasite which invades nests of Bombus affinis. Although parasites are limited by host worker defence to invading very small colonies, there is considerable flexibility in the way parasites control host brood bionomics once they are accepted inside the nest. A study of 46 parasitized and 22 non-parasitized laboratory colonies of B. affinis showed that P. ashtoni females cohabited with host queens and workers while the worker force increased, but not to the maximum normally achieved in non-parasitized nests. While colony reproductive success was correlated with the number of workers reared, parasites risked being killed or ejected from the comb by workers, after the queen had lost dominance. Host bees usually succeeded in rearing offspring, and Psithyrus reproductive success was related to the ability of parasites to control proportional investment in the two species. In addition to displacing P. ashtoni females, host bees ate the eggs of parasites and ejected their larvae. These behaviours were also exhibited by workers in the later stages of development of non-parasitized colonies. These results indicate that social parasites are at least partially subject to the conflict of genetic self-interest between the queen and her workers which is believed to influence the control of reproductive investment in haplodiploid Bombus societies.     

Temporal dynamics of facultative social parasitism in bumble bees (Hymenoptera: Apidae)

Parasitical behaviour is thought to play an important, yet so far largely unknown role in the evolution and maintenance of insect sociality. In this study, the influence of interspecific, facultative social parasitism upon bumble bee, Bombus, nesting biology was explored. Queens of B. affinis were introduced into 38 various-sized laboratory colonies of B. terricola. Foreign queens were very successful at killing the resident queen and usurping pre-worker nests (77% wins), although usurpation success decreased to 30% in colonies that contained workers. In addition, B. affinis queens were unable to suppress ovarian development in B. terricola workers that emerged prior to nest usurpation, resulting in the eventual death or expulsion of the foreign queen. In contrast, ovarian development was supporessed in workers that eclosed in the presence of a foreign queen, and in workers that were less than 5 h old when confined in small experimental boxes with a B. affinis queen. Foreign queens that usurped a nest prior to worker emergence were assisted by B. terricola workers, and achieved similar reproductive success when compared to a cohort of 22 B. affinis queens that initiated their own nests in the laboratory. These results suggest that there are periods in the ontogeny of Bombus nest defence, recognition and dominance during which bees are sensitive to the effects of nest parasitism. In bumble bees, and in other social insects, individuals of some species may exploit these weaknesses for their own reproductive benefit.     

Microsatellite loci for the stingless bee Melipona rufiventris (Hymenoptera: Apidae)

Eight microsatellite primers were developed from ISSR (intersimple sequence repeats) markers for the stingless bee Melipona rufiventris. These primers were tested in 20 M. rufiventris workers, representing a single population from Minas Gerais state. The number of alleles per locus ranged from 2 to 5 (mean = 2.63) and the observed and expected heterozygosity values ranged from 0.00 to 0.44 (mean = 0.20) and from 0.05 to 0.68 (mean = 0.31), respectively. Several loci were also polymorphic in M. quadrifasciata, M. bicolor, M. mandacaia and Partamona helleri and should prove useful in population studies of other stingless bees.     

Live Varroa jacobsoni (Mesostigmata: Varroidae) fallen from honey bee (Hymenoptera: Apidae) colonies

The proportion of Varroa jacobsoni Oudemans that were alive and mobile when they fell from honey bees, Apis mellifera L., in hives was measured during a 20-wk period to determine the potential use of systems that prevent these mites from returning to the bees. Traps designed to discriminate between the live, fallen mites and those that are dead or immobile were used on hive bottom boards. A large fraction of the fallen mites was alive when acaricide was not in use and also when fluvalinate or coumaphos treatments were in the hives. The live proportion of mitefall increased during very hot weather. The proportion of mitefall that was alive was higher at the rear and sides of the hive compared with that falling from center frames near the hive entrance. More sclerotized than callow mites were alive when they fell. A screen-covered trap that covers the entire hive bottom board requires a sticky barrier to retain all live mites. This trap or another method that prevents fallen, viable mites from returning to the hive is recommended as a part of an integrated control program. It also may slow the development of acaricide resistance in V. jacobsoni and allow the substitution of less hazardous chemicals for the acaricides currently in use.     

A preliminary cladistic investigation of relationships among the bumble bees (Hymenoptera, Apidae)

ABSTRACT. The cladistic method is used to classify sixty species of bumble bees by characters of the male genitalia selected for their functional importance. A system of three genera is recommended, preserving the holophyletic groups Mendacibombus Skorikov, Psithyrus Lepeletier and Bombus Latreille, with the retention of the named subgroups of Bombus in subgeneric status. A new subgenus Brachycephalibombus is recognized in order to avoid paraphyletic groupings. The phylogenetic interpretation of the cladogram is considered and biogeographic problems discussed.