Evidence of Entrance Sharing and Subterranean Connections in Andrena agilissima (Hymenoptera; Andrenidae)

Andrena agilissima is a bee that nests on sloped or vertical earth walls. Data from 3 years of fieldwork presented here show that this species is communal and uses the same nesting site for many years. On an earth wall on Isola d'Elba (Tuscany, Italy), covered with many bee nest entrances, we studied an aggregation of Andrena agilissima to determine if bees share entrances, if the sharing provides evidence for subterranean connections, and if bees involved in sharing show a division of labor. We marked several females coming out of the same entrance, as well as recapturing the same females using different entrances. No division of labor was observed in our observations.     

An interesting case of gynandromorphism in Andrena helvola (Linnaeus, 1758) (Hymenoptera: Apoidea: Andrenidae)

A gynandromorphic specimen of Andrena helvola (Linnaeus, 1758) having secondary sexual characters on the head is described.     

Effects of familiarity and nestmate number on social interactions in two communal bees, Andrena scotica and Panurgus calcaratus (Hymenoptera, Andrenidae)

Summary: Communality is considered a widespread form of social organization in bees and wasps, one in which two or more females of the same generation share a common nest and amongst whom there is no reproductive division of labor. The evolution and maintenance of egalitarian communal societies poses theoretical difficulties where 'cheating' amongst nestmates is practised. Yet there is little knowledge of the intranidal social interactions among communal conspecifics that allow an understanding of the degree of cooperation versus exploitation amongst nestmates in such societies. Using a circle-tube arena, we staged interactions in the laboratory among pairs of female conspecifics using two communal andrenid species, Andrena scotica and Panurgus calcaratus, to score their cooperative and aggressive behaviors. For both species, females did not discriminate between familiar (nestmate) and unfamiliar (non-nestmate) conspecifics in their cooperative and aggressive behaviors, suggesting that there is universal acceptance of conspecifics. Levels of cooperation and aggression did not vary with the number of nestmates in the nest of origin for either species. In addition, frequencies of social interactions did not vary with body size, wing wear or ovarian development in P. calcaratus. Interspecific comparisons were made with published data on social interactions of other bee species at varying levels of social organization (solitary to eusocial) derived from analogous circle-tube experiments. Panurgus calcaratus displayed highly cooperative behavior, similar to that of a previously studied communal bee, Lasioglossum hemichalceum (Kukuk, 1992a). Andrena scotica displayed lower levels of cooperation, and was in this sense more similar to solitary species and to interactions amongst non-nestmate individuals of eusocial species. Both A. scotica and P. calcaratus displayed very low levels of aggressive behavior, again similar to L. hemichalceum. As a working hypothesis, we suggest the existence of a communal behavioral syndrome comprising high levels of intranidal cooperation and low aggression, both directed indiscriminately at conspecifics.     

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.     

Strong genetic exchange among populations of a specialist bee, <Emphasis Type="Italic">Andrena vaga</Emphasis> (Hymenoptera: Andrenidae)

Habitat fragmentation is believed to be a key threat to biodiversity, with habitat specialists being stronger affected than generalists. However, pioneer species might be less affected by fragmentation, as their high colonization potential should increase gene flow. Here, we present an analysis of the genetic structure of populations of the solitary bee Andrena vaga, which naturally occurs in sandy habitats and is specialized on willow (Salix) pollen as larval food and sandy soils as nesting sites. While the species is widespread in the young sandy landscapes of our main study area (Emsland, northwestern Germany), it occurs less frequently in the Lower Rhine valley. Our analyses of six polymorphic microsatellites show that the populations are only slightly differentiated, suggesting a relatively strong gene flow. No genetic structure corresponding to the geographic origin was found as the variability within populations accounted for the major proportion of variation. F_ST values were higher and allelic richness was lower in the Lower Rhine valley, supporting the hypothesis that habitat availability affects the degree of genetic exchange between populations. Inbreeding coefficients were generally high and nearly all populations had a heterozygote deficiency, which could be explained by the breeding strategy of A. vaga, which nests in aggregations.     

Andinopanurgus, a new Andean subgenus of Protandrena (Hymenoptera, Andrenidae)

A new subgenus of Protandrena Cockerell (Panurginae: Protandrenini) from South America, Andinopanurgus Gonzalez & Engel, subgen. n., is described and figured for distinctive species of the genus occurring at mid- and high elevations in the Andes from Venezuela to Peru (1100-3400 m). In addition to the distribution, the subgenus is easily distinguished from other subgenera by a unique combination of morphological characters in both sexes, especially in the hidden sterna and genitalia of the male. Protandrena amyaesp. n., and Protandrena femoralissp. n., are also described and figured from the Ecuadorian and Peruvian Andes. New geographical records and a key to the species are also provided.     

Nesting and Biology of Alastor mocsaryi (Hymenoptera,Vespidae: Eumeninae)

Entomological Review - The nest structure of Alastor mocsaryi in trap nests was studied in Crimea. Fifteen nests were examined, located inside hollow reed stems 3.0–4.8 mm in inner diameter....     

Nesting biology of four Tetrapedia species in trap-nests (Hymenoptera: Apidae: Tetrapediini)

The nests used in this study were obtained from trap-nests (tubes of cardboard and cut bamboo stems) placed on Santa Carlota Farm (Itaoca Section-IS, Santana Section-SS and Cerrado-Ce), Cajuru, SP, Brazil. The number of nests and corresponding species obtained were as follows: 516 nests of T. curvitarsis, 104 of T. rugulosa, 399 of T. diversipes and 98 of T. gamfaloi. The most abundant species from SS and Ce was T. curvitarsis, and from IS it was T. diversipes. In general, most nests were collected during the hot and wet season (September to April). The nests were constructed with sand and an oily substance, and a single female established them. The cells were constructed in a linear series, sometimes followed by a vestibular cell. The number of brood cells ranged from 1 to 10 in T. curvitarsis (n=200), and in T. garofaloi (n-51), from 1 to 8 (n-30) in T. rugulosa, and from 1 to 6 (n=37) in T. diversipes. The pollen mass (pollen + oily substance) contained a hollow, sometimes divided by a transverse ridge, on the exposed face of the pollen mass. The egg was vertically positioned in the lower part of the hollow. At times, the closing of a cell was initiated before provisioning was completed, with a construction of a collar at the cell limit. In some nests the final cellular partition also acted as a closure plug. Females began activities at 6:18 a.m. and ended between 3:31 and 6:26 p.m. Some females (T. curvitarsis, T. rugiulosa and T. ganrfaloi) did not spend the nights at their nests, returning to them only the following morning with additional material. In general, the development period (for males and females) was greater in nests collected near the end of the hot and wet season than it was for nests collected in other months. Sex ratios for each species were as follows: T. curvitarsis. 1:1: T. rugulosa, 1.6:1 female; T. diversipes, 1.9:1: T. garofaloi, 2.8:1. Males and females of T. diversipes exhibited statistically similar sizes and in the other three species the females were larger than the males. The mortality rates were statistically similar: 33.2% for T. curvitarsis, 25.8% for T. rugulosa, 26.8% for T. diversipes and 38.2% for T. garnfaloi. The parasitoids were: Coelioxoides exulans, Leucospis cayenensis, Anthrax sp., Coelioxys sp., Coelioxoides sp. and individuals of the family Meloidae.     

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.     

Electron microscopic structure of the cephalic gland of the bee Andrena variabilis Smith (Hymenoptera: Apoidea)

The structure of the glandular tissue located beneath the eye sulcus in Andrena variabilis Smith was studied by means of light and electron microscopy. The glandular tissue was found to be constituted of single-layered, high cylindrical epithelial cells. Electron microscopy revealed strong foldings of the cell membrane on the basal pole of the gland cells. Next to the basal lamina, nerve fibres were found with great frequency. The central, perinuclear zone of the gland cells was rich in cell organelles. The lamellae of the rough-surfaced endoplasmic reticulum (rer) were mostly observed near the nuclear membrane. The vesicles and tubules of the smooth-surface endoplasmic reticulum (ser) were found to be congregated in contiguous compact regions. A well-developed and complicated canalicular system was enclosed between the rer and ser compartments, presumably serving as a passage for the secretory products. Membrane-bound electron-dense granules (secretory granules) were also a characteristic finding in the ser. In a small proportion of the gland cells, strong vacuolization indicated the degradation processes. From the light and electron microscopic characteristics of the gland cells, the existence of pheromone-producing secretory activity of exocrine type in the cephalic gland is presumed.     

Panurgines, novel antimicrobial peptides from the venom of communal bee Panurgus calcaratus (Hymenoptera: Andrenidae)

Three novel antimicrobial peptides (AMPs), named panurgines (PNGs), were isolated from the venom of the wild bee Panurgus calcaratus. The dodecapeptide of the sequence LNWGAILKHIIK-NH₂ (PNG-1) belongs to the category of α-helical amphipathic AMPs. The other two cyclic peptides containing 25 amino acid residues and two intramolecular disulfide bridges of the pattern Cys8–Cys23 and Cys11–Cys19 have almost identical sequence established as LDVKKIICVACKIXPNPACKKICPK-OH (X=K, PNG-K and X=R, PNG-R). All three peptides exhibited antimicrobial activity against Gram-positive bacteria and Gram-negative bacteria, antifungal activity, and low hemolytic activity against human erythrocytes. We prepared a series of PNG-1 analogs to study the effects of cationicity, amphipathicity, and hydrophobicity on the biological activity. Several of them exhibited improved antimicrobial potency, particularly those with increased net positive charge. The linear analogs of PNG-K and PNG-R having all Cys residues substituted by α-amino butyric acid were inactive, thus indicating the importance of disulfide bridges for the antimicrobial activity. However, the linear PNG-K with all four cysteine residues unpaired, exhibited antimicrobial activity. PNG-1 and its analogs induced a significant leakage of fluorescent dye entrapped in bacterial membrane-mimicking large unilamellar vesicles as well as in vesicles mimicking eukaryotic cell membrane. On the other hand, PNG-K and PNG-R exhibited dye-leakage activity only from vesicles mimicking bacterial cell membrane.     

Nesting and Biology of Eustenancistrocerus amadanensis (Hymenoptera,Vespidae, Eumeninae)

Entomological Review - The nest structure of Eustenancistrocerus amadanensis was studied in Crimea. Females nested in the ground, in level or gently sloping spots with sparse vegetation. The soil...     

Nesting Biology of Microstigmus thripoctenus Richards, with a Study on Nest Recognition (Hymenoptera: Crabronidae)

In a study carried out on Microstigmus thripoctenus on Barro Colorado Island (Republic of Panama) between March and May 1998, 29 active nests were located. The nests contained between one and seven cells, with one (female) to six (three females and three males) adults. Using simple manipulations in which wasps were offered a choice between experimentally emptied foreign nests and their own nest when the adults were away, it was observed that returning adults were able to recognize their own nest. Foreign nests were always rejected by females coming from nests with a single adult, whereas individuals from nests with several adults in five of seven cases did accept the foreign nests, continuing their normal activities in them, without destroying their contents. Adopted foreign nests were inspected at a higher rate following adoption. Nests containing several adults tended to remain longer on leaves supporting them, and their external surfaces were inspected more frequently and longer than those of nests containing only one occupant. Nests are not associated with any particular plant and were found attached to leaves of 19 species of understory plants.     

Nesting biology of three Megachile (Hymenoptera: Megachilidae) species from Eastern Amazonia,Brazil

Megachile Latreille is a conspicuous genus of solitary bees distributed worldwide. However, the biology of tropical species is still little known. We present data on biology of Megachile brasiliensis Data Torre, Megachile sejuncta Cockerell and Megachile stilbonotaspis Moure found in two remnants of eastern Amazonian forest in northeastern Brazil. The study was conducted using the trap-nest methodology in two different areas during four periods. We collected a total of 24 nests of M. brasiliensis, 26 of M. sejuncta and 28 of M. stilbonotaspis. The differential abundance of collected nests may reflect the population size in each sampled place. The nesting activity was concentrated mainly between July and January and species presented a multivoltine pattern, except for M. sejuncta, which was partly univoltine. Assessed pollen use showed a predominant use of Attalea sp. (Arecaceae) and, for M. stilbonotaspis, Tylesia sp. and Lepidaploa sp. (Asteraceae). Babassu is a very common palm in the studied areas and the studied species seem to have a strong link with it. We also reported change of pollen use by M. sejuncta, probably due to competition with M. brasiliensis, which may have influenced the biased sex ratio observed in M. sejuncta toward males. Parasites reported here were also recorded for other Megachile species, such as Coelioxys, Brachymeria, Meloidae and Pyralidae species. Mites were observed in association with M. stilbonotaspis. The data presented here set up a background that encourages new studies on the ecology of these three Amazonian species, providing tools for proper biodiversity management and conservation.     

Nesting Habit and Alarm Pheromones in Polistes gallicus (Hymenoptera, Vespidae)

Alarm pheromones are used in many social insects to elicit an alarm response of nestmates towards disturbances. This chemical alarm channel is especially used by species nesting in closed environments. Polistes gallicus paper wasps typically found their nests on open substrates where visual and vibrational stimuli could be more important than the chemical one to alarm the colony. We investigated, through field bioassays, if, also in this species, workers venom is still the source of alarm pheromones. Our results show that venom volatiles are able to increase the colony defence reaction stimulating more individuals to attack and sting the object of disturbance. Therefore our results suggest the hypothesis that chemical alarm is independent of nesting habit (concealed vs exposed) within the Polistes genus.     

Devasting effects of river flooding to the ground-nesting bee, <Emphasis Type="Italic">Andrena vaga</Emphasis> (Hymenoptera: Andrenidae), and its associated fauna

Large populations of non-social bees are rarely seen in today's cultural landscapes. One of the few exceptions is the fossorial bee Andrena vaga Panzer, (Andrenidae), a typical insect species of river flood plains, which forms sizeable nesting aggregations along the high water dams of the Upper Rhine, each containing up to several tens of thousands of bees. In May 1999, a record flood of the River Rhine led to extreme water levels at the high water dams of the Upper Rhine. Though natural flooding is often viewed as a management practice with considerable conservation perspectives for river flood plain management, we demonstrate a catastrophic effect of the 1999 inundation on the immature offspring of two affected populations of A. vaga. All immatures in brood cells located low on the landward side of a dam died, very likely because saturation of the soil restricted oxygen availability.The two affected aggregations sited on the high water dam declined in the following year to 23 and 56% of pre-flood size, but not at a neighbouring, non-flooded aggregation. Rare parasites associated with A. vaga also decreased in number following flooding. These results highlight a dilemma on the use of natural flooding of river plains for conservation purposes.