Nesting biology of the potter wasp Rhynchium brunneum brunneum (Fabricius, 1793) (Hymenoptera: Vespidae: Eumeninae) in North Vietnam

Rhynchium brunneum brunneum (Fabricius, 1793) is a common species using trap nests in North Vietnam. The females chose the nest traps with diameters ranging from 5.5 to 17 mm. Nests consisted of a linear series of one to eleven brood cells separated by mud partitions. Brood cells were provisioned with caterpillars, and eggs were attached to the ceiling of the cells by a thin filament. The life history and sex ratio data of this species were recorded from April to early November. Its sex ratio is strongly male-biased, being multivoltine, likely with four generations per year, the last one overwintering in the prepupal stage. Nesting activity of the species was described with major activities such as nesting site selection, oviposition, prey collecting, and applying cell material. Only 53.3% of the provisioned cells were successful; the others were damaged by six parasitoid species or died during development for unknown reasons.     

The natural history of the mud-dauber wasp Sceliphron fistularium (Hymenoptera: Sphecidae) in southeastern Brazil

Nests of Sceliphron fistularium were obtained in Colombia and Moji Gua?u, S?o Paulo, Brazil. Complete nests consisted of 1 to 54 sausage-shaped cells, arranged side by side along a horizontal axis, and found attached to electrical wires (Colombia, n = 7) and walls (Colombia, n = 4 and Moji Gua?u, n = 4). The number of cells per nest ranged from 1 to 54, their length varying from 20.8 to 29.7 mm, and their diameter from 7.6 to 11.7 mm. Brood cells were provisioned with spiders of the family Araneidae. Only Alpaida veniliae was collected in Colombia, whereas the most frequent species found in Moji Gua?u was Micrathena swainsoni (62.0%) followed by M. acuta (23.3%). Adults emerged from June to October. The length and diameter of female and male cells were similar. Nevertheless, females were significantly larger than males. The sex ratio of individuals obtained from nests was 1.16 females: 1 male. A life table was constructed, and details of the life cycle of the wasps and parasitoids are presented. The most common mortality factors were either unknown or due to the parasitoid wasp Melittobia sp.     

Biology of the solitary wasp Trypoxylon (Trypargilum) agamemnon Richards 1934 (Hymenoptera: Crabronidae) in trap‐nests

Buschini, M.L.T. and Fajardo, S. 2009. Biology of the solitary wasp Trypoxylon (Trypargilum) agamemnon Richards 1934 (Hymenoptera: Crabronidae) in trap‐nests. —Acta Zoologica (Stockholm) 91 : 426–432. Some Trypoxylon species build their nests in preexisting tubular cavities like hollow stems and beetle borings in branches. Study of the biology of these insects is relatively easy because the females of these wasps nest with enormous success in trap‐nests. The aim of this study was to investigate the abundance, seasonality and life‐history of Trypoxylon agamemnon. For capture of these insects, trap‐nests were installed in the Parque Municipal das Araucárias in araucaria forest, grassland and swamp, from December, 2001 to December, 2005. Two hundred and ninety seven nests were obtained. They were constructed more often during the summer (from December to April). The nests were built only in araucaria forest and consisted of a linear series of cells, divided by mud partitions, whose number varied from 1 to 7. Normally they have only one vestibular cell. The inner cells had been provisioned, usually with spiders of Anyphaenidae family. Sex‐ratio was strongly female biased. Its main natural enemies included Chrysididae, Ichneumonidae and Tachinidae.     

Nesting behavior of Podium denticulatum Smith (Hymenoptera: Sphecidae)

The nesting behavior of Podium denticulatum Smith was studied on the campus of Ribeir?o Preto of the Universidade de S?o Paulo, SP, Brazil, from September 2003 to August 2005. The wasps established their nests in bamboo canes ranging from 11.4 cm to 26.2 cm in length and from 0.7 cm to 1.8 cm in internal diameter. Podium denticulatum nested almost exclusively in the hot and wet season (September-April), producing at least five generations per year. The cell provisioning was made with adult and nymphal cockroaches (Blattellidae) which were arranged venter-up and with the head inward toward the inner end of the cell. The construction of a temporary closure occurred in cells that took more than one day to be provisioned. The cells provisioned with a greater number of prey were more likely to produce females than males. The nests included 1-6 brood cells separated by mud partitions and arranged in a linear series. The innermost cells of the nests produced females, and the outermost cells produced males. Nests were parasitized by Eulophidae (Melittobia sp.), Chrysididae and Tachinidae.     

Comparative aspects of the biology of five Auplopus species (Hymenoptera; Pompilidae; Pepsinae) from Brazil

This study was carried out at the Parque Municipal das Araucárias, in the municipality of Guarapuava, state of Paraná, southern Brazil, from December 2001 to December 2004. Sixty nests belonging to five Auplopus species were collected using trap-nests. The nest cells of all species were built with mud and shaped like a barrel or cylinder, mostly in linear arrangement. Differences between species lie in the colour of the mud and the way in which they organize the mud pellets during the construction of the cells. Few vestibular and intercalary cells were built. The number of cells varied according to the species, never surpassing six cells per nest. We observed a great variation between the five species related to sex ratio and the number of generations per year. Some species presented a delayed life cycle with juveniles entering diapause, others presented an additional short life cycle with no diapause.     

Life-history and sex allocation in Trypoxylon (syn. Trypargilum) lactitarse (Hymenoptera; Crabronidae)

Hymenopterans have become a model for the study of factors that govern sex allocation. In 1983, Seger proposed a model to study Sphecidae wasps with a strong prediction that sex ratio for univoltine wasps should be 1 : 1 (female : male), and for partially bivoltine species it should be male-biased. The present study investigates if Trypoxylon lactitarse (Saussure, 1867) is a univoltine or a bivoltine species and if Seger's model prediction fits the pattern of sex ratio found in this species. The study was carried out at Parque Municipal das Araucárias, in the municipality of Guarapuava, state of Paraná, southern Brazil, from December 2001 to December 2004. Nests of T. lactitarse were obtained using trap-nests drilled longitudinally to a depth to 80 mm with 7.0, 10.0 and 13.0 mm opening diameter. They were placed in a very heterogeneous site filled with araucaria forests, swamps and grasslands. Trypoxylon lactitarse showed two alternative life histories: either they pupated immediately and emerged as adults later in the same season (direct development), or they entered diapause, overwintering and pupating the following spring (delayed development). Its annual sex ratios were not significantly different from 1 : 1, and both sex ratio of overwintering and sex ratio of direct-developing wasps were also not significantly different from 1 : 1, in all years of this study. By examining these results, it was possible to conclude that although T. lactitarse is a multivoltine species, with four generations per year and two alternative life histories, its sex ratio did not support Seger's model.     

Nesting biology and nest re-use ofEulaema nigrita (Hymenoptera: Apidae,Euglossini)

Summary The nesting behavior of the euglossine beeEulaema nigrita was observed in the laboratory after being transferred from three nests to observation boxes. Nests were re-used by successive generations with more than one female working in each re-use process. Associated females were always of the same generation. All females that shared a nest foraged for construction materials (mud, excrement and resin) and each constructed, provisioned and oviposited in her own cells. The number of cells constructed by each female ranged from one to 23. Females stayed in the nests for periods ranging from 15 to 59 days during the hot and wet season and from five to 78 days during the cool and dry season. The egg-to-adult period was related to climatic conditions, and in all re-use processes it was longer than the time of residence of the females in the nests. The meloid beetleMeloetyphlus attacephalus was the only nest parasite. Due to the attack method employed by this parasite, the presence of more than one female in the nest did not result in improved nest defense.     

Nesting biology of four species of Trypoxylon (Trypargilum) (Hymenoptera: Crabronidae) in Chaco Serrano woodland, Central Argentina

Trypoxylon (Trypargilum) (Crabronidae) wasps are solitary spider predators that can build their nests in artificial trap-nests, which enables study of their nesting architecture and biology. Twenty traps (each containing 15-30 internodes of cane) were placed in each of nine sites of Chaco Serrano Woodland in Central Argentina (Córdoba) in October 2005, and were recovered in June 2006. We obtained 91 nests of four species of Trypoxylon (Trypargilum). In the laboratory, each Trypoxylon nest was sectioned longitudinally to study its architecture. The number of brood cells was counted, and the occurrence and length of vestibular and intercalary cells and the pre-closing plug space were recorded. We measured the diameter of the cane entrance, total length of the nest, length of each brood cell, maximum thickness of mud partitions and closing plug thickness. We also recorded the cell contents: the wasps, their natural enemies and the prey spiders. Mortality was assessed and the sex ratio calculated for each species. Finally, the nests were examined to help clarify the function of the vestibular cell. The nest architecture was similar in the four species, with linear brood cells located one after the other separated by mud partitions, as in other species of the subgenus Trypargilum. Forty-eight percent of the nests had vestibular cells, but only two had intercalary cells. The thickness of the mud partitions and the length of the brood cells differed among species and were related to the size of the emerged wasp. The diameter of the nest entrance was directly related to the average length of the fore-tibia. Sex ratios of all species did not deviate from 0.5. Mortality due to parasitoids (Eulophidae; Melittobia sp.) was similar among species, while the mortality due to cuckoo wasps (Chrysididae) in T. lactitarse was higher than in the other species. The presence of vestibular cells was not related either to the mortality due to natural enemies or to the orientation of the trap in the field. Spiders in the family Araneidae were the most frequently collected prey.     

The nest structure in four wasp species of the genus Euodynerus Dalla Torre (Hymenoptera, Vespidae: Eumeninae)

A comparative analysis of the main parameters of the nest structure and composition in Euodynerus quadrifasciatus, Eu. dantici, Eu. disconotatus, and Eu. velutinus in the Crimea is given. Nests of all the studied species were obtained from trap-nests made of reed stems; the nests of Eu. dantici and Eu. disconotatus were additionally obtained from the abandoned cells of the nests of Sceliphron destillatorium. The nest of Eu. quadrifasciatus consists of a consecutive row of cells, each cell having its own bottom and lid with empty space between them; the nests of three other species consist of an uninterrupted row of cells without spaces, so that the cell bottoms act as partitions. The data on the diameter and length of nest cavities occupied by the studied species, the number of cells in nests, the sex ratio and the length of the cells with prospective females and males are reported. The correlations between the length of the cells and the diameter of the occupied cavities and between the length of the rear empty nest space and vestibule and the length of the occupied nest cavity are analyzed. The structure of cocoons and final nest plugs are described. The difference in the evolution of nest building instincts in members of the subgenera Pareuodynerus and Euodynerus s. str. and the role of adaptation to nest tenantry in the evolution of nest building instincts of Eu. dantici and Eu. disconotatus are discussed.     

The nesting of Osmia rufa (L.) (Hymenoptera, Megachilidae) in the Crimea: Structure and composition of nests

The structure and composition of nests of Osmia rufa have been investigated. The weight of the septa between the cells increases regularly from the first to the last cell, whereas the length of cells and weight of the pollen loaf decrease. The difference of weight between cells of males and those of females is sharper. The number of cells and weight of cocoons with adults decrease in the series of nests built by the same female during the nesting season, and the sex ratio shifts to males. Abundant food resources facilitate an increase in the average weight of the offspring, the number of cells, and shift of the sex ratio toward females. The mechanism of the sex ratio regulation in O. rufa nests includes three consecutive elements. The key element is the presence of a marker of the switching to making low-weight pollen loafs. This marker is the moment of the “overloading” of the last cell in a row of cells intended for future females. Daughters of large females are smaller, and those of small females, larger than their mothers. The probable cause of this discrepancy is the allometric relation between the female’s weight and its working capacity.     

Absence of Complementary Sex Determination in the Parasitoid Wasp Genus Asobara (Hymenoptera: Braconidae)

An attractive way to improve our understanding of sex determination evolution is to study the underlying mechanisms in closely related species and in a phylogenetic perspective. Hymenopterans are well suited owing to the diverse sex determination mechanisms, including different types of Complementary Sex Determination (CSD) and maternal control sex determination. We investigated different types of CSD in four species within the braconid wasp genus Asobara that exhibit diverse life-history traits. Nine to thirteen generations of inbreeding were monitored for diploid male production, brood size, offspring sex ratio, and pupal mortality as indicators for CSD. In addition, simulation models were developed to compare these observations to predicted patterns for multilocus CSD with up to ten loci. The inbreeding regime did not result in diploid male production, decreased brood sizes, substantially increased offspring sex ratios nor in increased pupal mortality. The simulations further allowed us to reject CSD with up to ten loci, which is a strong refutation of the multilocus CSD model. We discuss how the absence of CSD can be reconciled with the variation in life-history traits among Asobara species, and the ramifications for the phylogenetic distribution of sex determination mechanisms in the Hymenoptera.     

The nesting biology of the bee, Osmia dimidiata Morawitz, 1870 (Hymenoptera, Megachilidae) in the Crimea

The structure and composition of Osmia dimidiata nests were studied based on the material of 133 nests obtained from trap-nests in five localities of the Crimea. The nests contained from 1 to 9 cells (on average, 2.2), separated with partitions made of masticated leaves. Most of the cells had a massive hemispherical bottom and a thin flat cover. The final plug had a structure similar to the cell bottom. The cells occurred singly in the nest cavity or were arranged in rows of 2 or 3 cells separated by galleries. The diameter of the occupied cavities was positively correlated with the fraction of the females in the progeny and with the mass of the cocoons, but negatively correlated with the cell length. The cells with females were 1.5 times as long as those with males. The cocoons with females were twice as heavy as those with males. The peculiar characters of the nest structure of O. dimidiata may mean that the typical nesting substrates of this species are abandoned cells of other bee and wasp species. The characteristic mechanism of estimating the mass of the pollen loaf stored in the cells and determining the brood sex ratio has evolved in the O. dimidiata due to its tenantry. This mechanism is based on two constants: the sex-linked cell length and the fixed distance between the pollen loaf and the cell cover. When choosing the nesting cavities, the female prefers broader and longer tubes for cells with females and narrower and shorter ones for cells with males. The overall sex ratio of the progeny was male-biased (1 ♀: 2.5 ♂) and depended on the food supply abundance. The adults of O. dimidiata fly in the Crimea from the last decade of May until the end of July. Hibernation occurs at the adult stage in the cocoons. Females collect pollen from flowers of Asteraceae or, rarely, Fabaceae. The nests may be destroyed by Melittobia acasta, Monodontomerus aereus, M. obscurus, Sapyga quinquepunctata, Stelis phaeoptera, and Trichodes apiarius; 21% of the progeny died from these enemies, and 22%, due to other factors. The previously proposed synonymy of Pseudosmia taurica Radoszkowski, 1874 (nec Osmia taurica Radoszkowski, 1887) and O. dimidiata is rejected.     

Group nesting and individual variation in behavior and physiology in the orchid bee <Emphasis Type="Italic">Euglossa nigropilosa</Emphasis> Moure (Hymenoptera,Apidae)

The Euglossini are a key group for studying the traits that promote or hinder highly social behavior in bees because it is the only tribe in the Apine clade without large colonies or females with distinct life histories, e.g. queens and workers. There have been few studies on behavior of orchid bee females in nests because these nests are not found easily. Taking advantage of the relatively high abundance of Eg. nigropilosa nests at Reserva Natural La Planada, Colombia, we examined social behavior of Eg. nigropilosa individuals in five nests (3 original and 2 reused) for nine months. We report this species to have the largest colonies known for Euglossa, with nests reaching up to 22 individuals, and all nests containing more than one female bee from the same generation. These nests presented many traits that correspond to communal insect colonies. No generational overlap and no cooperative brood care were detected. We examined natural enemies and resource limitation as important factors for group nesting. We examined parasitoid attacks to cells in a nest with females and one without females. We also searched for nesting locations and examined nest re-use as indicators of nest site limitation. Lastly, we examined behavioral and physiological differences among females in the same nest. Such differences could be the bases for evolution of alternative life histories among group living females. We examined extent of ovary development and oviposition rates in similarly aged females in the same nest. We found large variation in reproductive effort of young females. We also examined differences in resin foraging and cell usurpation behaviors. Behavioral specialization was observed, with some individuals bringing only resin to the nest. Inside the nests, bees had territories in which they constructed and defended cells. This territoriality may be a defense against usurpation of provisioned cells by nest mates. Received 10 December 2007; revised 2 May 2008; accepted 7 May 2008.     

The nest structure in four species of solitary wasps of the subfamily Eumeninae (Hymenoptera, Vespidae)

Nests of Syneuodynerus egregius, Euodynerus posticus, Ancistrocerus antilope, and A. nigricornis have a similar structure and consist of a linear row of cells separated by transverse partitions made of soil mastic. The number of cells in the nests is 1–11 (5.6 ± 0.8) in S. egregius, 1–7 (2.6 ± 0.2) in E. posticus, 1–10 (4.0 ± 0.7) in A. antilope, and 1–28 (7.9 ± 1.3) in A. nigricornis. Most nests consist of several cells in S. egregius and A. nigricornis and of one or two cells in E. posticus and A. antilope. The female to male ratio is 1.2: 1.0 in E. egregius, 1.5: 1.0 in E. posticus, 1.9: 1.0 in A. antilope, and 1.0: 1.0 in A. nigricornis. The nests of S. egregius usually contain brood of both sexes; those of A. antilope, that of one sex. The sex ratio is correlated with the diameter of the occupied nest cavities only in A. antilope. The volume of the cells with females exceeds that of the cells with males in all the species studied: by 23, 34, 54, and 98% in S. egregius, E. posticus, A. antilope, and A. nigricornis, respectively. The relative difference between the body masses of male and female prepupae is correlated with the relative difference between the volumes of their cells. The nest cells of S. egregius are separated by double partitions consisting of homologs of cell bottoms and lids. In the nests of E. posticus the partitions are single; each cell has a bottom and a lid, with “false cells” being located between them. In the nests of A. antilope and A. nigricornis, the partitions are single but all of them are homologs of the cell bottoms. The nest cells of S. egregius belong to the equilinear type; their length is relatively constant in the cavities of various diameters. The nest cells of A. antilope are of the equivolumetric type: their length is smaller in broad cavities and greater in narrow ones, the cell volume being relatively constant in the cavities of different diameters. The nest cells of E. posticus and A. nigricornis are of the intermediate type. Statistical models of nests reflecting their mean parameters and composition were built. The evolutionarily primitive and progressive features in the nest structure are discussed.     

A report of progressive provisioning in a stink bug,Parastrachia japonensis (Hemiptera: Cydnidae)

The majority (75%) of femaleParastrachia japonensis (Hemiptera: Cydnidae), while caring for 1st and 2nd instar nymphs, foraged for and provisioned nests with drupes of the host plant,Schoepfia jasminodora (Olacacae), which the young then fed on. The maximum number of drupes found in a given nest was 27. Females could travel as fast as 61.4 cm/min while carrying drupes that were nearly double their weight, and were directly observed to travel as far as 10 m when encumbered with a drupe. It was found that nests which were far from the food source were provisioned with at least as many drupes as those nests that were within the drupe range. While females could not distinguish their own eggs from others, apparently they could distinguish their own nests containing their nymphs. Eggs failed to survive in the absence of a female, however, a small number of nymphs reached adulthood even in the absence of a female when drupes were provided. This report represents the first direct observation of progressive provisioning by a phytophagous hemipteran under field conditions.     

Host-parasite relationships in six species ofSphecodes bees and their halictid hosts: Nest intrusion,intranidal behavior,and Dufour's gland volatiles (Hymenoptera: Halictidae)

Nest invasion behavior was studied in six kleptoparasiticSphecodes species at four nesting sites of their respective social and solitary hosts.Sphecodes females preferred to enter unguarded nests. Nest intruding strategies observed in the differentSphecodes species did not depend on whether host species were solitary or social, as long as the nesting cycle of a social host was in the solitary stage (i.e., a single host female). Observation of intranidal behavior revealed thatSphecodes monilicornis females kill all host individuals within an usurped nest. They stay in the nest for several hours, laying eggs in adequately provisioned brood cells. Gas chromatography-mass spectrometry analyses of Dufour's gland secretions revealed species-specific compositions. Qualitative comparisons of whole patterns and quantitative comparisons considering the predominant hydrocarbons common to both host and parasite contradict the hypothesis of chemical mimetism, a mechanism supposed to permit parasite intrusion by qualitatively similar odor bouquets in host and parasite females.     

First Data on the Bionomics of the Solitary Wasp <Emphasis Type="Italic">Leptochilus membranaceus</Emphasis> (Morawitz) (Hymenoptera,Vespidae: Eumeninae)

The bionomics of Leptochilus membranaceus (Morawitz) was studied in Crimea. The species is confined to herbaceous xerophytic habitats with sparse vegetation and has two generations per year. Adult feeding was recorded on flowers of 8 plant species of 6 families. A single nest was found in an old acridid egg pod in clayey soil. The inner cavity of the empty egg pod was 12 mm long and 3 mm wide. The nest contained one cell with a prepupa in the cocoon. The cell was sealed with a final plug 2 mm thick, made of gravel and mud. The cocoon consisted of three equal thin layers, the outer layer being firmly attached to the cell walls. Females of L. membranaceus do not visit water sources. The origin of the agent bonding the building material (soil) used by L. membranaceus and other congeneric species is discussed. In addition, nests of Ancistrocerus scoticus (Curtis) are also discussed; these nests occur in old acridid egg pods which were earlier misinterpreted as bottle-shaped cells built by the wasps themselves.     

Nomadic behaviour and colony fission in a cooperative spider: life history evolution at the level of the colony?

The concept of colony-level life history evolution is introduced for the cooperative spiders by describing the life cycle and demography of Atbuhna binotata (Araneae: Dictynidae), a species living in groups containing up to several dozen adult females plus their offspring. In a life cycle remarkably similar to that of army ants, the colonies of A binotata were found to reproduce by fission and to alternate nomadic and sedentary phases in tight association with their internal demography. Colonies of other cooperative spiders, on the other hand, remain stationary as they grow for a number of generations before producing propagules that are relatively small subsets of the maternal colony. It is suggested that A. binotata!% peculiar life cycle may have unfolded as a consequence of the two-dimensional architecture of its nests. Expanding two-dimensional nests may fragment more easily than the three-dimensional nests characteristic of other species. A long distance group migration or nomadic phase, described here for the first time for a spider, may have followed as a mechanism to cope with potential disadvantages of fission while selecting for strict synchronization of individual life cycle stages within the nests. It is shown, however, that, as in other cooperative spiders, A. binotatd% sex ratio is also highly female biased. The theoretical implications of biased sex ratios in a species with fissioning colonies are briefly discussed.     

Seasonal nest characteristics of a facultatively social orchid bee,Euglossa viridissima,in the Yucatan Peninsula,Mexico

Euglossines have long been regarded as largely solitary, though some species are known to exhibit social behavior. We studied the nesting behavior of Euglossa viridissima over an annual cycle, comparing sociality and offspring production across the rainy (RS) and dry seasons (DS) in the Yucatan Peninsula of Mexico. Nests were built in both the RS and the DS, but with greater nest initiation and brood provisioning in the RS, presumably as a consequence of more floral resources at this time of year. Across the year, numerical sex ratios were female biased (0.7 as females/total); sex ratios varied across individual nests from 0.3 to 1.00, though without a clear relationship to sociality. Egg-to-adult development was quicker in females than males and, within a sex, quicker when ambient temperatures were higher. Multi-female (social) nests were only founded at the end of the RS and the beginning of the DS, coincided with the presence of Hymenopteran and Dipteran parasites in nests headed by solitary females. Reduced floral resources and a higher risk of parasitism, possibly coupled with higher female density or reduced nesting sites, may be factors favoring the formation of multi-female associations in this euglossine. Better nourishment of foundress females in the RS may improve lifespan and permit overlapping generations which, coupled with the kin structure of their nests, may favor social nesting in E. viridissima.     

Relationships between Nest Architecture and Behavior in <Emphasis Type="Italic">Xylocopa virginica</Emphasis> (Hymenoptera: Apidae)

The large carpenter bees nest in reeds, stems and wood. Many other Hymenoptera, including many wasps and some bees, have strong associations between the physical elements of their nests and behavior. Nests of the North American carpenter bee, Xylocopa virginica, were collected in southern Ontario. Nest architecture elements were examined with respect to their impact on life-history elements. In particular, it was determined that the brood cells are provisioned sequentially both within and among branches. There was also no detectable pattern of sex allocation in broods. Nests with branched architecture contained more foundresses, but these foundresses did not appear to contribute in the construction of larger nests. These findings are discussed with respect to other bees, and to the social structure of Xylocopa virginica.