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 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.     

Nest site selection and efficacy of artificial nests for breeding success of Scarlet Macaws Ara macao macao in lowland Peru

Psittacidae (parrots) have the most threatened species of any bird family in the world. Most parrots are obligate secondary cavity nesters, and can be limited in their breeding success by the availability and quality of nest hollows. However, nesting opportunities for parrots can be increased by provision of artificial nest boxes. The Tambopata Macaw Project has been studying the breeding ecology and natural history of the Scarlet Macaw Ara macao macao in the south-eastern Peruvian Amazon for over 20 years by monitoring natural nest hollows and two types of artificial nest (wooden and PVC). We present data for breeding success in natural and artificial nests over 12 consecutive breeding seasons. The aims of this study were to: (a) determine the nesting requirements and reproductive success of breeding macaws; and, (b) compare the efficacy of the two types of artificial nests and natural nest cavities. Our data showed a high rate of reoccupation of successful nests in consecutive years and that nests in artificial and natural nests had very similar reproductive parameters. Our results indicate that artificial nest types can be used by conservation managers seeking to assist A. macao populations where nest hollows are in short supply, and that artificial nests can contribute important data to natural history studies of species where access to natural nests is limited.     

Nesting and biology of Jucancistrocerus caspicus (hymenoptera,vespidae, eumeninae)

Females of Jucancistrocerus caspicus nest in dense clay ground on the vertical surface of cliffs. The nests contain 1–9 cells (on average 2.8) and have a linear-branched construction. Females surmount the entrance of the burrow with a curved chimney which has a laced structure. The cells are positioned vertically in the main burrow and obliquely or horizontally in the lateral tunnels; the cells in a row are separated with double partitions. The size of the cells is 7–9 × 4–4.5 mm, the diameter of the nest burrow is 4 mm. The egg is laid before provisioning and is attached to the cell ceiling with a filament. Females hunt for weevil larvae and store 23–33 larvae (on average 27.8) in each cell. The species is univoltine, with prepupae hibernating in their cocoons. The nests are parasitized by the cuckoo wasps Chrysis rutilans which cause 11.5% of brood mortality. Adult wasps are killed by the spiders Pholcus sp. living near the nests.     

Few, small, and male: multiple effects of reduced nest space on the offspring of the solitary wasp, Euodynerus (Pareuodynerus) posticus (Hymenoptera: Vespidae)

The size of the preexisting wood cavities used as nests by aculeate Hymenoptera is expected to have consequences on fitness parameters such as offspring number and size. We evaluated the consequences of using small and large (three-times more voluminous) trap-nests by the solitary wasp, Euodynerus (Pareuodynerus) posticus (Herrich-Schaeffer). Following life-history and sex allocation theories, a number of non-mutually exclusive hypotheses were formulated: i.e. small nests either produce smaller or fewer offspring and/or more males, the cheaper sex. Wasps built about 28% more, but shorter brood cells in large nests, although their volume was still much higher in large nests. Adult males had smaller body size in small nests, but female size did not differ between large and small nests, possibly as an adaptive response against the future higher foraging costs of size-reduced females. Sex-ratio was often biased towards males in small nests. Mortality did not differ between large and small nests. We conclude that E.?(P.) posticus females would benefit from using larger nests, but that the sex-ratio would be probably overall unbalanced if females would not use also smaller, male-oriented tunnels.     

The bacterial and fungal nest microbiomes in populations of the social spider Stegodyphus dumicola

Social spiders of the species Stegodyphus dumicola live in communal nests with hundreds of individuals and are characterized by extremely low species-wide genetic diversity. The lack of genetic diversity in combination with group living imposes a potential threat for infection by pathogens. We therefore proposed that specific microbial symbionts inhabiting the spider nests may provide antimicrobial defense. To compare the bacterial and fungal diversity in 17 nests from three different locations in Namibia, we used 16S rRNA gene and internal transcribed spacer (ITS2) sequencing. The nest microbiomes differed between geographically distinct spider populations and appeared largely determined by the local environment. Nevertheless, we identified a core microbiome consisting of four bacterial genera (Curtobacterium, Modestobacter, Sphingomonas, Massilia) and four fungal genera (Aureobasidium, Didymella, Alternaria, Ascochyta), which likely are selected from surrounding soil and plants by the nest environment. We did not find indications for a strain- or species-specific symbiosis in the nests. Isolation of bacteria and fungi from nest material retrieved a few bacterial strains with antimicrobial activity but a number of antimicrobial fungi, including members of the fungal core microbiome. The significance of antimicrobial taxa in the nest microbiome for host protection remains to be shown.     

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.     

Artificial covering on trap nests improves the colonization of trap-nesting wasps

To evaluate the role that a trap‐nest cover might have on sampling methodologies, the abundance of each species of trap‐nesting Hymenoptera and the parasitism rate in a Canadian forest were compared between artificially covered and uncovered traps. Of trap tubes exposed at eight forest sites in six trap‐nest boxes, 531 trap tubes were occupied and 1216 individuals of 12 wasp species of four predatory families, Vespidae (Eumeninae), Crabronidae, Sphecidae and Pompilidae emerged over 2 years, and no bee species were found. Results indicated that artificial covering led to a significant increase in the number of nested tubes of Ancistrocerus adiabatus, Ancistrocerus antilope, Ancistrocerus campestris and Auplopus mellipes, and significant effects of covering were not found for the other species. No significant difference in the overall parasitism rate between covered and uncovered traps was noted. These suggested that the covering technique could provide more opportunities for some wasp species to colonize trap nests.     

Behaviour of female common cuckoos, Cuculus canorus, in the vicinity of host nests before and during egg laying: a radiotelemetry study

We radiotracked 13 common cuckoo females in the southeastern part of the Czech Republic. Seven females laid eggs in the nests of reed warblers, Acrocephalus scirpaceus, sedge warblers, A. schoenobaenus, and marsh warblers, A. palustris. We observed 53 nest visits, of which 26 involved egg laying. Cuckoos spent significantly more time within 50 m of the host nest on the laying day than on the 5 prelaying days. The vantage point used when parasitizing or visiting a nest was on average four times further from the nest than the closest possible vantage point, but there was a positive correlation between these two distances. Cuckoos spent on average 20 min observing host nests from their vantage points before they visited a nest. Comparison of cuckoos' visits to host nests with and without egg laying revealed no significant differences in the duration of visits or in other measures of behaviour. There was significant variation in behaviour between cuckoos, particularly in the time of day when eggs were laid in host nests. This variation can be attributed to the strong, but not absolute, host and habitat specificity of individuals. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Horizontal transmission of a parasitic nematode from a non-native to a native woodwasp?

In eastern North America, the exotic invasive woodwasp, Sirex noctilio, attacks pines (Pinus spp.) and often shares larval habitat with the native woodwasp, Sirex nigricornis. The parasitic nematode, Deladenus siricidicola, has been used widely in the southern hemisphere as a biological control agent because it sterilizes female S. noctilio. This nematode was introduced accidentally to North America along with S. noctilio. Historical reports indicate nematode-woodwasp fidelity: the parasitic nematode, D. siricidicola, exclusively infects S. noctilio, and the native nematode, Deladenus proximus, exclusively infects S. nigricornis. From two sites in southern Ontario, separated by 225 km, we collected woodwasps from three Pinus sylvestris, and identified the nematode species present in the abdomens of infected wasps. Both wasp species co-occurred in all three trees. D. siricidicola was present in the haemocoel, but not inside the eggs, of infected S. noctilio and S. nigricornis. This evidence suggests horizontal transmission of D. siricidicola likely occurred from S. noctilio to S. nigricornis.     

State-dependent decisions in nest site selection by a web-building spider

Foraging decisions may reflect a trade-off between food intake and safety and can also be influenced by the animal's internal state. Foraging in the web-building spider Stegodyphus lineatus depends on a capture web associated with a retreat (the nest). The relocation of nests, including the take-over of conspecific nests, may be viewed as a foraing decision, which depends on risk of exposure, cost of silk production and hunger state. We investigated a possible state-dependent trade-off in nest site choice of S. lineatus spiderlings. The philopatric nature ofS. lineatus implies a high risk of encounters with potentially cannibalistic conspecifics and a potential loss of inclusive fitness because encountered conspecifics are likely to be kin. To test for state dependence of foraging decisions, we compared preferences of well-fed and hungry spiders for their own nests and those of siblings and nonsiblings. We expected satiated spiders to prefer their own to conspecific nests and hungry spiders to choose the risky option of a conspecific nest. SinceS. lineatus is less aggressive towards kin, we tested the ability of spiders to discriminate kin by silk-bound cues. Because of this reduced aggression, preference for kin nests should be safer than preference for nonkin nests. A strong preference for self-nests demonstrated self-recognition in well-fed spiders. However, neither well-fed nor hungry spiders discriminated between nests of siblings and nonsiblings. Well-fed spiders preferred self-nests to empty chambers, but showed no discrimination between nonself-nests and empty chambers. Hungry spiders showed a reduced preference for self-nests, suggesting that hunger elicits a more risky foraging strategy. A tendency of hungry spiders to adopt the nests of conspecific spiders may reflect a silk-saving strategy. We conclude that S. lineatus spiders show state-dependent decision making in nest site selection. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Variation in social behavior within a spider mite genus, Stigmaeopsis (Acari: Tetranychidae)

The spider mites belonging to the genus Stigmaeopsis constructextremely dense oval woven roofs (web-nests) over depressionson the lower surface of host leaves and are known to have akind of sociality. The four species that occur on bamboo plantsin Japan show different nest areas. The nest area of Stigmaeopsislongus is the largest, followed by that of S. celarius, S. takahashii,and S. saharai in decreasing order. Smaller nests effectivelyprevent adults of several predator mite species from intruding.We hypothesized that variation in nest size reflects differentanti-intruder adaptations of this mite group in relation totheir sociality. The larger nest makers may adopt an alternativeanti-intruder strategy, namely, counterattack by a large group,so as to compensate for the disadvantage of large nests. S.longus and S. celarius adults effectively defended their largenests against potential predators, and the effects of nest defenseincreased with the number of individuals in a nest. S. takahashiiand S. saharai revealed no counterattack effect. Counterattackabilities that increase with the adult density, and thus, socialitymay compensate for the vulnerability of larger nests.     

Fidelity Among Sirex Woodwasps and Their Fungal Symbionts

We report that associations between mutualistic fungi and their economically and ecologically important woodwasp hosts are not always specific as was previously assumed. Woodwasps in the genus Sirex engage in obligate nutritional ectosymbioses with two species of Amylostereum, a homobasid\iomycete genus of white rot fungi. In the present study, the Amylostereum species and genotypes associated with three species of Sirex native to eastern North America and one relatively recent invasive Sirex from Europe were investigated by comparing intergenic spacer regions (IGS). Sirex spp. were sampled over 6 years from 23 sites in six US states, ranging from Maine in the northeast to Louisiana in the southeast, to obtain samples of Amylostereum from mycangia of adult females. Two of the native Sirex species (Sirex nigricornis and Sirex nitidus) were associated with either Amylostereum chailletii or Amylostereum areolatum, refuting the hypothesis of strict species-specific relationships. However, the invasive Sirex noctilio and the native Sirex cyaneus were each collected with only A. areolatum or A. chailletii, respectively, although S. noctilio was associated with two different IGS genotypes of A. areolatum and S. cyaneus occurs sympatrically with the other native Sirex. In Pinus, the preferred host tree of S. nigricornis and S. noctilio, these species co-occurred in 25.9 % of trees sampled, and horizontal transmission of fungal strains from S. noctilio to S. nigricornis was documented, although only in one tree. The extent that further spread and establishment of S. noctilio will alter the composition of symbionts carried by native Sirex is unknown but will depend in part on the degree of flexibility in these host–symbiont associations.     

Nesting biology of Pareumenes quadrispinosus (de Saussure, 1855) (Hymenoptera: Vespidae: Eumeninae) in trap nests in North Vietnam

Nests of Pareumenes quadrispinosus (de Saussure, 1855) were obtained at Me Linh Station for Biodiversity (323 nests) and Tam Dao Town (283 nests), Vinh Phuc Province, as well as at Phu Luong, Thai Nguyen Province (9 nests) and Kim Boi, Hoa Binh Province (62 nests). The wasps nested in segments of bamboo canes and reed stems, 5 to 18 mm in internal diameter. Each nest consisted of a linear series of one to four cells, separated by mud partitions. Brood cells were provisioned with caterpillars and eggs were attached to the ceiling of the cells by thin threads. The life history and sex ratio of this species nesting in trap nests in North Vietnam were recorded from mid-April to last October. The species is multivoltine, with likely up to four generations per year. It has two alternative life histories (diapause and direct development) and overlapping generations. The sex ratio is strongly female-biased. Only 46% of the provisioned cells were successful; the others were damaged by nine parasitoid species or died during development for unknown reasons.     

Nest preference and ecology of cavity-nesting bees (Hymenoptera: Apoidea) in Punjab,Pakistan

Among bees, 85 % are solitary species, most of them are ground-nester and some are cavity-nesting and construct their nests in pre-existing cavities. This work was conducted to evaluate the substrate preference and nest architecture (acceptance, occupation percentage, seasonality and parasitism) of cavity-nesting bees in different substrates. Trap nests offered comprised five different materials (drilled cavities in wood, bamboo, cardboard tubes, plastic soda straws, and mud blocks). These were installed in four districts for two years. The nesting cavities of five different diameters (6, 8, 10, 12 and 14 mm) were provided in each nesting material with an average length of 180 ± 9.92 mm. In all the materials, 5400 nesting cavities were offered, out of which 628 were colonized by bees from two families (Megachilidae and Apidae) and six species (Megachile cephalotes, M. lanata, M. bicolor, Xylocopa basalis, X. fenestrata and Ceratina smaragdula), including one parasitic bee (Euaspis carbonaria). The bee species differed significantly in occupying five nesting materials. The most preferred diameters were 8 mm and 10 mm, with 52.20% and 29.45% of colonization, respectively. Nesting was done throughout the year except in winter. This study will serve as a baseline for future studies and conservation programs of cavity-nesting bees in Pakistan.     

Thermal fluctuation within nests and predicted sex ratio of Morelet’s Crocodile

Understanding the interplay between thermal variations and sex ratio in reptiles with temperature-dependent sex determination is the first step for developing long-term conservation strategies. In case of crocodilians, the information is fragmentary and insufficient for establishing a general framework to consider how thermal fluctuation influence sex determination under natural conditions. The main goal of this study was to analyze thermal variation in nests of Crocodylus moreletii and to discuss the potential implications for predicting offspring sex ratio. The study was carried out at the Centro de Estudios Tecnológicos del Mar N° 2 and at the Sistemas Productivos Cocodrilo, Campeche, Mexico. Data was collected in the nesting season of Morelet’s Crocodiles during three consecutive seasons (2007-2009). Thermal fluctuations for multiple areas of the nest chamber were registered by data loggers. We calculate the constant temperature equivalent based on thermal profiles among nests to assess whether there are differences between the nest temperature and its equivalent to constant temperature. We observed that mean nest temperature was only different among nests, while daily thermal fluctuations vary depending on the depth position within the nest chamber, years and nests. The constant temperature equivalent was different among and within nests, but not among survey years. We observed differences between constant temperature equivalent and mean nest temperature both at the top and in the middle of the nest cavities, but were not significantly different at the bottom of nest cavities. Our results enable examine and discuss the relevance of daily thermal fluctuations to predict sex ratio of the Morelet’s Crocodile.     

Major benefits of guarding behavior in subsocial bees: implications for social evolution

Parental care is a behavior that increases the growth and survival of offspring, often at a cost to the parents' own survival and/or future reproduction. In this study, we focused on nest guarding, which is one of the most important types of extended parental care; we studied this behavior in two solitary bee species of the genus Ceratina with social ancestors. We performed the experiment of removing the laying female, who usually guards the nest after completing its provisioning, to test the effects of nest guarding on the offspring survival and nest fate. By dissecting natural nests, we found that Ceratina cucurbitina females always guarded their offspring until the offspring reached adulthood. In addition, the females of this species were able to crawl across the nest partitions and inspect the offspring in the brood cells. In contrast, several Ceratina chalybea females guarded their nests until the offspring reached adulthood, but others closed the nest entrance with a plug and deserted the nest. Nests with a low number of provisioned cells were more likely to be plugged and abandoned than nests with a higher number of cells. The female removal experiment had a significantly negative effect on offspring survival in both species. These nests frequently failed due to the attacks of natural enemies (e.g., ants, chalcidoid wasps, and other competing Ceratina bees). Increased offspring survival is the most important benefit of the guarding strategy. The abandonment of a potentially unsuccessful brood might constitute a benefit of the nest plugging behavior. The facultative nest desertion strategy is a derived behavior in the studied bees and constitutes an example of an evolutionary reduction in the extent of parental care.     

Nest Site Selection by Greater Sage-Grouse in Mono County,California

ABSTRACT Loss of nesting habitat is believed to be a factor in the decline of greater sage-grouse (Centrocercus urophasianus) throughout its range. Few data are available for sage-grouse in Mono County, California, USA, in the most southwestern portion of the species’ range. We studied habitat selection of nesting sage-grouse in Mono County, California, from 2003 to 2005 by capturing and radiotracking females to identify nesting locations. We sampled vegetation at nest sites and randomly selected sites within 200 m of nests and within each of 5 subareas within Mono County. Nest sites were characterized by 42.4 ± 1.3% (x̄ ± SE) shrub canopy cover, 10.5 ± 1.0 cm residual grass height, and 2.7 ± 1.0% residual grass cover. Shrub cover was the only variable found to differentiate nest sites from randomly selected sites. Unlike some other studies, we did not find understory vegetation to be important for selecting nest sites. Mean shrub cover was 38.7 ± 1.5% at random sites within 200 m of nests and 33.6 ± 1.6% at random sites at the approximate scale of home ranges, indicating that nesting females selected nesting areas that contained denser shrubs than their home range, and nest sites that contained greater shrub cover than the vicinity immediately surrounding nests. Our results suggest that managers should consider managing for greater shrub cover in Mono County than what is currently called for in other parts of sage-grouse range and that management for sage-grouse habitat may need to be tied more closely to local conditions.     

Termitarium volume as a determinant of invasion by obligatory termitophiles and inquilines in the nests of Constrictotermes cyphergaster (Termitidae, Nasutitermitinae)

A range of organisms can be found inside termite nests where the degree of association can vary from facultative to obligatory dependence. Studies of the dynamics of nest invasion are still unresolved, so how and when cohabitants enter termite nests remain open questions. This study analyzed one specific aspect of the dynamics of termite nest invasion by obligatory termitophiles and inquilines, i.e., whether cohabitants were more likely to invade a nest when it reached a critical nest size. We collected 36 Constrictotermes cyphergaster nests of different sizes and sampled their cohabitant fauna. Our results indicated that the invasion of C. cyphergaster nests by obligatory termitophiles and inquilines was dependent on nest size. There appeared to be a critical nest size above which nests were more prone to invasion. Above this size, there was a significantly higher likelihood of finding obligatory cohabitants. Termitophile species were observed in nests ≥2.2?L, whereas inquiline species were only occur in nests ≥13.6?L. This may indicate that the obligatory cohabitants studied here did not occupy C. cyphergaster nests at random and that they were dependent on features that made these nests suitable for cohabitation, which are linked to colony development.