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.     

Nesting biology of tropical solitary and social sweat bees,Lasioglossum (Dialictus) figueresi Wcislo andL. (D.) aeneiventre (Friese) (Hymenoptera: Halictidae)

Summary The nesting biology of a mainly solitary bee,Lasioglossum (Dialictus) figueresi, is compared with that of a possible relative and mainly eusocial bee,L. (D.) aeneiventre. These bees nest in the ground in highly disturbed areas in the Meseta Central of Costa Rica. Information is provided on social organization, male production, diel and seasonal activity patterns, pollen utilization, natural enemies and nest architecture. L. (D.) figueresi nests within aggregations in vertical earthen banks, and 80–90 % of females are solitary during the nest-provisioning phase. Social nests contain two (or rarely three) females which may be either equal or unequal in reproductive status (i.e. mated with developed ovaries or not). Solitary nests and two-female nests do not experience different rates of parasitism. Mid-way through the dry season, females cease provisioning at a time when otherL. (Dialictus) remain active. Females typically remain within their nests, although they occasionally forage for nectar. This behavior is similar of that of spring gynes of temperate eusocial species. The egg-to-adult developmental rate ofL. (D.) figueresi is unusually slow for halictine bees, however, so that all the adult females die before their brood eclose in April and May, precluding overlap of generations. The eclosed offspring remain in open cells within their natal nests until mid-June, when both males and females emerge to mate. These newly mated females either establish new nests or re-use old ones. L. (D.) aeneiventre nests within aggregations in horizontal ground or in vertical banks. A foundress female digs a nest at the beginning of the dry season, although some re-activate old nests. Foundress nests develop into colonies with various kinds of social organization. In contrast toL. (D.) figueresi, L. (D.) aeneiventre is active nearly all year round, except during periods of heavy rain, and produces up to three broods per year.Sweat bees (Hymenoptera: Halictinae) are a socially heterogeneous group of mainly ground-nesting bees which are abundant world-wide. Intra-specific variation in social behavior is prevalent both within and among populations, presumably indicating social and environmental control of behavioral modifications (see e.g. Sakagami and Munakata, 1972; Eickwort, 1986; Packer, 1990; Yanega, 1988; reviewed in Michener, 1990). The initial stages of hymenopteran social evolution are represented by solitary individuals and those in undifferentiated societies, yet their biology is not well known, as is true for the numerous tropical halictine species or populations (see Michener, 1990).The subgenusDialictus ofLasioglossum is a primarily New World group of several hundred species (Moure and Kurd, 1987). These bees are monotonously similar in structure and appearance, yet diverse in social behavior. FemaleLasioglossum (Dialictus) figueresi are usually solitary, and structurally are very similar to their social relativeL. (D.) aeneiventre (Wcislo, 1990 a). The systematic placement of these species with respect to otherL. (Dialictus) is uncertain, but they have no obvious affinities to other recognized species groups (G. C. Eickwort, pers. comm.). Unusual morphological features, such as large size, yellowish wings and pubescence, and features of the genital organs, may indicate thatL. (D.) figueresi is the more derived of the pair, and may therefore be secondarily solitary, as is known for other sweat bees (Packer, 1991).     

Dual phylogenetic origins of Nigerian lions (Panthera leo)

Lion fecal DNA extracts from four individuals each from Yankari Game Reserve and Kainji‐Lake National Park (central northeast and west Nigeria, respectively) were Sanger‐sequenced for the mitochondrial cytochrome b gene. The sequences were aligned against 61 lion reference sequences from other parts of Africa and India. The sequence data were analyzed further for the construction of phylogenetic trees using the maximum‐likelihood approach to depict phylogenetic patterns of distribution among sequences. Our results show that Nigerian lions grouped together with lions from West and Central Africa. At the smaller geographical scale, lions from Kainji‐Lake National Park in western Nigeria grouped with lions from Benin (located west of Nigeria), whereas lions from Yankari Game Reserve in central northeastern Nigeria grouped with the lion populations in Cameroon (located east of Nigeria). The finding that the two remaining lion populations in Nigeria have different phylogenetic origins is an important aspect to consider in future decisions regarding management and conservation of rapidly shrinking lion populations in West Africa.     

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.     

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.     

Environmental influences on male production and social structure inHalictus rubicundus (Hymenoptera: Halictidae)

Summary Several years' observations of population of a primitively social halictine bee,Halictus rubicundus, revealed the following: (1) there is a correlation between ambient temperatures during the spring provisioning phase and the sex ratio of the resulting brood, such that warmer temperatures are associated with an increase in male bias; (2) over the course of the season, the degree of male bias of eggs laid appears to correspond with photoperiod; and (3) increasing male bias in the first brood is associated with decreasing proportions of social colonies formed in the population, and this effect may be accentuated by small population size. These phenomena suggest that abiotic environmental conditions at the time of brood production may profoundly influence the demography of this population, and that the demography in turn determines the degree to which sociality is expressed. These findings are related to hypotheses dealing with caste determination in temperate halictine bees, viewed in the context of the evolution and maintenance of sociality, and it is proposed that these phenomena reveal a mechanism by which social behavior (the occurrence of a worker caste, in particular) is facultatively fine-tuned to suit the characteristics of the environment.     

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.     

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.     

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.     

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.     

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.     

Some North American parasites ofAclerda (Hymenoptera,Encyrtidae)

Résumé L'auteur décrit, dans cette note, deux espèces nord-américaines d'Encyrtides, parasites de cochenilles du genreAclerda: Mayridia ferrierei, obtenue deAclerda xalapenseae Mcconnell, etAenasioidea ferrierei, obtenue deA. andropogonis Mcconnell. Chez les deux espèces d'Encyrtides, les males sont ailés, tandis que les femelles possèdent des ailes plus ou moins réduites.      

A review of the bee genus Augochlorella (Hymenoptera: Halictidae: Augochlorini)

Abstract. The New World halictid bee genus Augochlorella (Augochlorini) is revised. Sixteen species are recognized, with five described as new: Augochlorella acarinata sp. n., A. una sp. n., A. meridionalis sp. n., A. stenothoracica sp. n. from South America, and A. karankawa sp. n. from U.S.A. The following new synonymies are proposed: Augochlorella michaelis (Vachal) with A. urania (Smith), A. edendata Michener with A. comis (Vachal); A. striata (Provancher) with Augochlorella aurata (Smith) and A. neglectula maritima Ordway with A. neglectula (Cockerell). The female of A. tredecim (Vachal) and the male of A. iopoecila Moure are described for the first time. Keys to the species are provided. Cladistic analysis of adult morphological characters corroborates Engel's hypotheses of monophyly of Augochlorella phylogenetic relationships with related genera as follow: (Augochlorella ((Ceratalictus, Pereirapis) Augochlora)). Vicariant events shown in the cladistic analyses are discussed, and an account of distribution is presented.