Does variation in female body size affect nesting success in Dawson’s burrowing bee,Amegilla dawsoni (Apidae: Anthophorini)?

Abstract.  1. Females of Dawson's burrowing bees vary in body weight over a twofold range. Despite the potential for differences in body weight to affect several aspects of the competition among nesting females, no clear advantages were documented for larger females.
2. Nesting females were not consistently larger than emerging females, nor was there a consistent relationship between body size and the weight of pollen and nectar carried to the nest on provisioning trips. At one nesting location, larger females did not produce larger pre-pupal offspring nor did they produce offspring at a faster rate than their smaller nesting companions.
3. In addition, large body size was not associated with greater success in nest defence despite the fact that nesting females regularly encountered intruders in their burrows. Residency, not body size, determined the outcome of almost all contests for control of a nest burrow. The absence of a large body size effect here appears to stem from an intruder strategy designed to enable nest-searching females to acquire burrows that had been abandoned through death or dispersal of their original owners rather than securing existing nests through an aggressive takeover strategy.
4. Thus, although large body size conveys significant fitness advantages to males, this attribute does not promote female success in either provisioning or defending their nests.     

Biology of <Emphasis Type="Italic">Lasioglossum</Emphasis> (<Emphasis Type="Italic">L.</Emphasis>) <Emphasis Type="Italic">majus</Emphasis> (Hymenoptera: Halictidae), a largely solitary sweat bee with behavioural adaptations to communality

Within the bee family Halictidae there have been three origins of sociality. Although detection of origins and reversal from sociality requires phylogenetic studies, at a behavioural level a predisposition to sociality can be detected by analysis of intra-specific interactions. We studied aspects of nesting biology and behavioural interactions in Lasioglossum (Lasioglossum) majus, a poorly known halictine inhabiting temperate regions of Europe, which is suspected to be solitary. Nests were found to be largely used by one female, but some were shared by more than one individual. These few nests, whose entrances were very close to each other, were found to be connected underground. A few individuals were observed to enter in a nest where a female was waiting, behaving as a guard and allowing the incoming bee to enter the nest. By use of circle-tube experiments, the behavioural repertoire exhibited by females during encounters was assessed. Levels of withdrawal and cooperative events were comparable with those observed in other solitary nesting species, but aggressive events were very rare, as in several observed communal species. We conclude that L. (L.) majus females, despite general solitary nesting, possess behavioural components enabling them to adopt, probably in high nest-density areas, nest-sharing strategies. A similar kind of local social polymorphism has been observed in two other species of the subgenus Lasioglossum, but these are the first data available on a European species and the first record of subterranean connections among nests of halictid bees.     

Floating and fidelity in nest visitation byCrawfordapis luctuosa (Hymenoptera: Colletidae)

We studied nest visitation behavior of the ground-nesting beeCrawfordapis luctuosa (Colletidae) at the Monteverde Cloud Forest Preserve, Puntarenas Province, Costa Rica. Some females entered many nests, while others consistently entered only one nest. Multiple nest entry was exhibited by bees we called floaters, and those bees that consistently entered only one nest were provisioning bees. Provisioning bees abandoned their old nests after provisioning periods and became nonprovisioning bees that floated over the nesting area. Floating behavior was a nest-searching behavior typified by oscillating flights just above the ground (<15 cm). Floaters investigated available nests and were not observed to interact aggressively with nest owners. Upon establishing a new nest, floaters became provisioning bees.     

Dyadic relationships in nesting males of the three-spined stickleback, Gasterosteus aculeatus

Multidimensional scaling analysis of nest site location, nesting interval, and aggressive and mating interactions revealed that male three-spined sticklebacks, Gasterosteus aculeatus, formed nesting clusters comprising five patterns of dyadic relationships. These patterns were defined by intervening variables such as size difference between the two males, nest site locations, synchronization of nesting cycles (egg presence in the nest), distance between two nests, and nest raiding behaviours. Several patterns of dyadic relationships were integrated among nesting males and their constellations indicated an expression of the social structure. Through an understanding the social structure, I described effects of social context or situations on individual reproductive success.     

An ecological analysis of mating biology of Xylocopa virginica in southern Ontario

1. Xylocopa virginica virginica Linnaeus is a wide‐ranging species with plastic nesting behaviour that appears to represent an intermediary between solitary and social nesting species. Over 3 years, a natural population was studied with the objective of quantifying the relationship among population dynamics, climate, female nest provisioning behaviour, and male mating strategy. 2. Males in the population congregated around female‐occupied nesting sites before the beginning of nest provisioning by females; both resident and satellite male mating strategies were observed. Overall, the present results are consistent with female defence polygyny. 3. Male mating strategies were consistent across the three breeding seasons of our study, in spite of annual variation in population size, sex ratio, and weather. Male mating behaviour was also consistent with that seen in other populations with longer breeding seasons. 4. Adult non‐breeding females that never leave nests are observed in nests throughout the breeding season and we hypothesise that males continue to defend territories after breeding females have mated because of a small probability they can mate with one of these non‐breeding females. 5. These results are important to our understanding of the relationship between mating systems and the evolution of sociality, contributing data on the role of ecological factors to male mating behaviour. Collection of such data for a variety of species that differ in sociality is necessary for the comparative analysis that is required to fully elucidate coevolution of mating systems and sociality.     

Soil temperature, digging behaviour, and the adaptive value of nest depth in South American species of Acromyrmex leaf-cutting ants

In leaf-cutting ants, workers are expected to excavate the nest at a soil depth that provides suitable temperatures, since the symbiotic fungus cultivated inside nest chambers is highly dependent on temperature for proper growth. We hypothesize that the different nesting habits observed in Acromyrmex leaf-cutting ants in the South American continent, i.e. superficial and subterranean nests, depend on the occurrence, across the soil profile, of the temperature range preferred by workers for digging. To test this hypothesis, we first explored whether the nesting habits in the genus Acromyrmex are correlated with the prevailing soil temperature regimes at the reported nest locations. Second, we experimentally investigated whether Acromyrmex workers engaged in digging use soil temperature as a cue to decide where to excavate the nest. A bibliographic survey of nesting habits of 21 South American Acromyrmex species indicated that nesting habits are correlated with the soil temperature regimes: the warmer the soil at the nesting site, the higher the number of species inhabiting subterranean nests, as compared to superficial nests. For those species showing nesting plasticity, subterranean nests occurred in hot soils, and superficial nests in cold ones. Experimental results indicated that Acromyrmex lundi workers use soil temperature as an orientation cue to decide where to start digging, and respond to rising and falling soil temperatures by moving to alternative digging places, or by stopping digging, respectively. The soil temperature range preferred for digging, between 20°C and maximally 30.6°C, matched the range at which colony growth would be maximized. It is suggested that temperature-sensitive digging guides digging workers towards their preferred range of soil temperature. Workers’ thermopreferences lead to a concentration of digging activity at the soil layers where the preferred range occurs, and therefore, to the construction of superficial nests in cold soils, and subterranean ones in hot soils. The adaptive value of the temperature-related nesting habits, and the temperature-sensitive digging, is further discussed.     

双斑切叶蜂的筑巢习性

【目的】明确双斑切叶蜂Megachile leachella在沙地上的筑巢环境及筑巢特点,旨在当地利用人工巢管诱引其筑巢。【方法】采用目测和拍照等方法对双斑切叶蜂的整个筑巢过程进行了连续观察; 采用挖掘、测量方法对双斑切叶蜂巢内结构进行了观测;在室内对蜂茧在土中和指形管中的羽化情况进行了初步观测。【结果】双斑切叶蜂一般在废弃的泥墙或者沙地上蚂蚁等废弃的巢穴中筑巢,有时候它也在沙地上挖掘新巢筑巢。双斑切叶蜂用叶片构建巢室,一巢多室,各巢室首尾相接排列在巢中,筑完巢后用叶片将巢口封住。双斑切叶蜂构建一个巢室需要切取11～14片叶子,为每巢室采集蜂粮6～9次,每巢室内产卵1粒;在内蒙古毛乌素沙地,该蜂一年2代,第1代在6月中下旬羽化,第2代大约在7月下旬至8月上旬羽化,主要寄生性天敌有尖腹蜂Coelioxy sp.、青蜂Chrysis sp.。双斑切叶蜂能在指形管中羽化。【结论】双斑切叶蜂不同个体之间的筑巢行为相似,雌蜂可以用人工巢管进行诱集和驯化。     

The Nesting Behavior of Dawson's Burrowing Bee, Amegilla dawsoni (Hymenoptera: Anthophorini), and the Production of Offspring of Different Sizes

Females of Dawson's burrowing bees have a well-defined brood cell cycle involving cell construction, waxing, provisioning, egg laying, and cell capping. In one study population, nesting bees built smaller brood cells for offspring of lower weight and larger ones for heavier offspring, demonstrating their ability to anticipate the desired size of an offspring at the outset of a brood cell cycle. Furthermore, individual females varied the number of provisioning trips made per brood cell cycle by a factor of two or more, apparently exercising control over the amount of brood provisions supplied to an offspring. The size distribution of emerging males at two widely separated locations in 1997 was nearly identical to that recorded in 1995. These findings suggest that the production of small males (minors) is the result of active female control rather than the product of food shortages that force females to undersupply some brood cells. Female foraging decisions resulted in a bimodal distribution of weights of mature dormant larvae at one site in 1997. However, the times required to complete brood cell cycles at this site were not distributed bimodally. This result stemmed in part from daily variation among females in the duration of their provisioning trips as well as from seasonal variation in provisioning trip times. When provisioning trips lasted longer, females tended to make fewer trips per brood cell cycle, and so were presumably more likely to produce minor sons. As a result, the weight of an offspring was not tightly linked to the time investment required to produce it, making it difficult to compare the relative costs of minors and majors in terms of maternal time investments.     

Intraspecific nest parasitism in the sand waspStictia heros (Fabr.) (Hymenoptera: Sphecidae)

Two forms of intraspecific nest parasitism are described for the neotropical sand waspStictia heros (Fabr.). Females behaving aggressively made aerial attacks on prey-laden females as they approached their nest for provisioning. Attacks resulted in prolonged grappling on the sand, and the relative sizes of the contestants influenced final possession of the prey. Also, the probability that returning females were attacked was directly related to the size of the prey being delivered. Females displaying marauding behavior entered the nests of other females, removed prey, and deposited it in their own nest. Females usually raided nests that were near their own nest and tended to concentrate raiding attempts on nests that previously yielded prey. We also describe the behavior associated with the delivery of hunted prey and examine possible interrelationships between wasp size, prey size and hunting trip duration.     

Communal egg-laying behaviour and the consequences of egg aggregation in the brown anole (Anolis sagrei)

Communal nesting is a behaviour that involves multiple females laying eggs in the same nest or nesting site. This behaviour may be a consequence of a shortage of preferable nest sites (constraint hypothesis) or an adaptation generated by fitness benefits associated with egg aggregation (adaptive hypothesis). Experimental tests of these hypotheses require information about maternal nest site choice and its fitness consequences. To address these, we studied a lizard (brown anole; Anolis sagrei) that produces single-egg clutches, but often aggregates eggs in nest sites. In a lab study, females were given the option of nesting in (a) soil previously used as nest substrate vs. fresh soil and (b) soil with eggshells vs. without eggshells. We also experimentally examined the effects of egg aggregation by incubating eggs singly, in groups of four, and in groups of nine. We recorded egg surface temperature, water uptake, and hatchling morphology. Females were more likely to nest in pots with used soil and with eggshells than in pots with fresh soil or without eggshells. We observed no effects of egg aggregation on egg survival, egg temperature, or most measures of hatchling morphology. However, singly-incubated eggs absorbed more water than eggs incubated in the four and nine egg aggregations and this resulted in offspring with greater body condition (i.e. heavier for their length) at hatching. The behavioural experiment demonstrates that females actively choose nest sites that have been used previously (as expected under the adaptive hypothesis), but the egg-aggregation experiment shows no benefits to offspring based on the variables measured. Thus, results of the behaviour study support the adaptive hypothesis; however, results from our egg-incubation study do not. Likely, the adaptive and constraint hypotheses are not mutually exclusive, and a diversity of factors influence the evolution of communal nesting behaviour.     

An overview of proximate factors affecting the nesting behavior of solitary wasps and bees (Hymenoptera: Aculeata) in preexisting cavities in wood

Guilds of Aculeate solitary wasps and bees that nest in preexisting cavities in wood are important components of terrestrial ecosystems because they engage in several ecological interactions (e.g. predation and pollination) with other species of plants and animals. Spatial and temporal variations in richness and abundance of solitary wasps and bees can be related to changes in environmental structure and in the diversity of other groups of organisms. The nesting period of these Aculeata is their most critical life cycle stage. Females of solitary wasp and bee species invest relatively more time constructing and provisioning their nests than do females of social species. Differently from species that nest in the soil or construct exposed nests, the main factors affecting the reproductive success of solitary species nesting in preexisting wood holes are still unknown. Our objective is to provide an overview of the role of proximate causes of nesting failure or success among solitary wasps and bees (Aculeata), for designing effective conservation and management strategies for these Hymenoptera.     

The discovery of hatching and transition to feeding young by male Mountain Bluebirds

In many bird species, only females incubate the eggs, but both sexes feed nestlings. The means by which males of such species discover hatching and transition to feeding their offspring remains almost completely unexplored. Of particular interest are species with nests whose contents are concealed from view. During June and early July 2015 in the Bighorn Mountains of Wyoming, we used continuous video‐recording of nests of cavity‐nesting Mountain Bluebirds (Sialia currucoides) to document the transition to feeding young by males. We saw no evidence that females used distinct vocal or visual displays to signal hatching to males. Observing mates carrying eggshells away from, or food into, nest boxes did not appear to trigger provisioning by males. Rather, at all 24 nests observed, males did not begin feeding until they had come to nest boxes and presumably sensed the presence of hatchings directly. Individual males varied, however, in both the manner in which they inspected nest contents and the number of times they did so before starting to feed young. Although most males fully entered nest boxes where they could see, touch, hear, and possibly smell hatchlings (or eggshell parts), other males may have detected hatchlings only by sound or possibly smell while perched at a nest‐box entrance. Based on past studies of mice and doves, we suggest that, for provisioning behavior to begin, some kind of direct sensation of offspring may be necessary to activate relevant neurons in the medial preoptic area of the hypothalamus of males, an area of the brain important in parental care. Additional research is necessary to test this, and to examine the effects of factors such as hormone levels and breeding experience on the means and rapidity by which males discover hatching and transition to nestling provisioning.     

Nest Building and Mating in Relation to Male Size in Corkwing Wrasse, Symphodus Melops

This study examines nest building and mating in relation to size in male corkwing wrasse, Symphodus melops, in the absence of male–male competition. We kept males of varying size together with mature females in tanks containing adequate materials and sites for nest construction. Our results indicate that the size of territorial males does not influence the ability to construct a nest. However, larger males initiated nest building earlier than smaller males and nest size correlated positively with male size. Furthermore, male size did not affect whether or not a nesting male succeeded in mating, indicating that male size was not essential for female acceptance (i.e. whether or not a female is willing to mate) of a male in the current situation.     

Size-mediated dominance and aggressive behavior of male Japanese fluvial sculpin Cottus pollux (Pisces: Cottidae) reduce nest-site abundance and mating success of conspecific rivals

Despite growing evidence for plasticity in the mating patterns of nest-holding animals in relation to the changes in nest abundance, the effects of aggressive interaction by dominant males on nest availability for conspecific rivals remains unclear. To quantify the effects of male–male competition on nest-site choice and mating success of the male Japanese fluvial sculpin Cottus pollux, we conducted experiments on 5 males from different 5 size classes under both sufficient and shortage nest-abundance conditions. Nest-choice experiments showed that both male size class and nest-abundance condition had significant effects on the nesting rates of males. Following the nest-choice experiments, 10 gravid females were added in the experimental tanks. Mating experiments revealed that male size, nesting rate before addition of females, and the number of courtship attempts on females were valid variables of male mating success, regardless of nest-abundance conditions. After achieving initial mating success, the largest nesting male exhibited more frequent aggressive interaction with other conspecific males than he did before obtaining eggs in his nest. Our results suggest that size-mediated dominance and aggressive behavior of males may disrupt nest acquisition of other conspecific males, and may consequently result in extreme variation in mating success among males even under sufficient nest-abundance conditions.     

The biology of the mud-wasp Zeta abdominale (Drury) (Hymenoptera: Eumenidae)

The adult female nesting behaviour and biology of the neotropical mud-wasp Zeta abdominale (Drury) was studied in Jamaica. The cell-building behaviour was generally similar to that of Eumenes, but Zeta closed the apical funnel of the cell by moistening and re-moulding it into a plug. Each nest was built by a solitary female, who often built several small, mostly one-celled nests. Females efficiently used mud in cell-building, and small nests were advantageous, in needing less mud per cell and incurring a lower rate of predation than larger nests. Cellwall construction and provisioning were each completed in < 3 h, but a long pause between these activities, probably for feeding, delayed cell completion to 2.33 ± 1.0 days.
The number of active nesting females during a 10-h cycle was influenced by the time of day and weather. A relatively dense population had about 6.4 females ha^-1, whose age distribution, longevity and fecundity were estimated.     

Evolution of nesting behaviour and kleptoparasitism in a selected group of osmiine bees (Hymenoptera: Megachilidae)

The construction of nests to rear offspring is restricted to vertebrates and few insect taxa, such as termites, wasps, and bees. Among bees, species of the family Megachilidae are characterized by a particularly high diversity in nest construction behaviour. Many megachilid bees nest in excavated burrows in the ground, others place their brood cells in a variety of above‐ground cavities or attach them to the surface of a substrate, and yet others have adopted a kleptoparasitic habit. Evolutionary transitions between the different nesting sites and between conventional nesting and kleptoparasitism in bees are poorly understood. In the present study, we traced the evolution of nesting site selection and kleptoparasitism in the Annosmia–Hoplitis group (Osmiini), which displays an exceptionally high diversity in nesting behaviour. We found that the evolution of nesting behaviour proceeded unidirectionally from nesting in excavated burrows in the ground to nesting in rock depressions and cavities, followed by the colonization of snail shells and insect borings in dead wood or hollow stems. Kleptoparasitism evolved once and the kleptoparasitic species have derived from the same lineage as their hosts. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 108 , 349–360.     

The behaviour of Philanthus crabroniformis (Hymenoptera: Sphecidae)

Observations were made over a two year period on the nesting and hunting behaviour of a population of Philanthus crabroniformis Smith. Data are presented on the time and speed of provisioning, the capture of prey and the species taken, the design and location of nests, the approach to the nest with prey, and aggressive interactions between females. P. gibbosus Fabr., also nested in the same area and took much the same prey. Unlike other sympatric pairs of Philanthus which have been studied, the two species in question were not totally segregated by separate nesting seasons nor by mutually exclusive habitat preferences. One aspect of the behaviour of the two Philanthus which was highly distinctive was the manner in which prey-laden females approached their nests. Selection for divergence in approach patterns may have been exerted by miltogrammine flies, a major parasite of many digger wasps.     

Ability to assess nest predation risk in secondary hole-nesting birds: an experimental study

Because nest predation is the major source of nesting mortality in birds, site-specific predation risk may play an important role in determining birds' ability to select nest sites that reduce predation risk. This possibility has not been adequately tested. Here we report on 5-year experiments by which we studied, independently from birds' earlier experience with specific nest boxes, both the selection and predation risk of nest sites in the common goldeneye (Bucephala clangula). New, previously unoccupied nest boxes were erected in two habitat types on three study areas. Experimentally measured predation risk in the nest boxes varied between 0 and 1.0, i.e. goldeneye females could select a nest site along a wide gradient of possible predation-risk values. We did not find a difference in predation risk between occupied and unoccupied nest boxes, nor was the order of nest box occupation associated with predation risk. A power analysis revealed that our test had reasonably high power to reject a false null hypothesis. Our results suggest that common goldeneye females likely have not evolved an ability to assess predation risk of new, previously unoccupied nest sites.     

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.