Nest Sanitation in Social Spider Mites: Interspecific Differences in Defecation Behavior

Nest sanitation behavior is an important adaptation in nest‐building animals. The social spider mite Stigmaeopsis miscanthi (Saito) constructs woven nests on the leaf undersurface of perennial pampas grass (Miscanthus sinensis Anderss) and lives in the nests in large groups. Nest members of this species defecate at only one site inside the nest for nest sanitation, and the waste management is maintained by volatile chemical and tactile cues. Other members of the genus Stigmaeopsis Banks also construct woven nests, live in groups, and manage their fecal wastes, but the species differ in nest and group size, host plant, and social behavior. We investigated the details of waste management in four Stigmaeopsis spp. and found differences in the location of the defecation site and in the way each species recognizes this site. Like S. miscanthi, Stigmaeopsis longus defecates at only one site and uses volatile chemical and tactile cues, whereas Stigmaeopsis takahashii and Stigmaeopsis saharai both defecate at two sites and use only tactile cues. We discuss the reasons for the waste management differences within the genus, and the relationship between the means of waste management, nest and group size.     

Evolutionary view of waste-management behavior using volatile chemical cues in social spider mites

Spider mites of the genus Stigmaeopsis (Acari: Tetranychidae) construct and live gregariously inside woven nests on the leaf surface of host plants. This genus shows waste-management behavior—they defecate at particular sites—but the rules for management differ between species. The utilization of chemical cues for waste management is known in two species, Stigmaeopsis miscanthi inhabiting Miscanthus sinensis and S. longus inhabiting Sasa senanensis, but not in any others. In this study, we first investigated the origin of the chemical compounds to understand how the behavior evolved, and then investigated the responses of each species to chemical compounds from different sources. The results show that the chemical compounds are commonly contained in the feces of several Stigmaeopsis species, as well as in their host plant juices, suggesting this behavior evolved using the chemical compounds originally contained in their feces. Our results also show that the chemical compounds used by S. miscanthi and S. longus are subtly different and involve host plant differences, and that S. miscanthi could respond to both compounds, but S. longus could not. Considering this in terms of their phylogenetic relationship, it is expected that these two species may have evolved from a common ancestor living on Sasa senanensis.     

Habitat characteristics and species interference influence space use and nest‐site occupancy: implications for social variation in two sister species

Nest‐site selection is an important component of species socio‐ecology, being a crucial factor in establishment of group living. Consequently, nest‐site characteristics together with space‐use proxies may reveal the social organization of species, which is critical when direct observation of social interactions is hindered in nature. Importantly, nest‐site choice is expected to be under strong selective pressures and the object of intra‐ and interspecific competition. Although the bulk of research on sociality focuses on its ecological drivers, our study introduces interspecific competition as a potential factor that could influence social evolution. We investigated the influence of habitat and interspecific competition on the social organization of two sister species of the African four striped mouse, Rhabdomys dilectus dilectus and Rhabdomys bechuanae, in a similar macroenvironment. These species diverged in allopatry and occupy distinct environmental niches. We radiotracked 140 adults to identify their nest‐sites, determine nest characteristics and record groups that shared nest‐sites. Group cohesion was estimated from nest‐site fidelity, group association strength, and home range overlap within versus between group members. We compared the two species in sympatry versus parapatry to determine the impact of species interference on sociality. In parapatry, the two species selected distinct nest‐site types, interpreted as different anti‐predator strategies: R. bechuanae selected fewer, spaced, less concealed nest‐sites whereas R. d. dilectus selected clumped and less visible nest‐sites. Rhabdomys bechuanae also showed more cohesive and stable social groups than R. d. dilectus. In sympatry, compared to R. bechuanae, R. d. dilectus occupied similar nest‐sites, however slightly more exposed and clumped, and displayed similar nest‐site fidelity and group association strength. We conclude that although habitat selection may be an important driver of social divergence in Rhabdomys, species interference, by limiting R. d. dilectus movements and forcing nest‐site sharing may induce new ecological pressures that could influence its social evolution.     

Distinguishing signals and cues: bumblebees use general footprints to generate adaptive behaviour at flowers and nest

Chemicals used in communication are divided into signals and cues. Signals are moulded by natural selection to carry specific meanings in specific contexts. Cues, on the other hand, have not been moulded by natural selection to carry specific information for intended receivers. Distinguishing between these two modes of information transfer is difficult when animals do not perform obvious secretion behaviours. Although a number of insects have been suspected of leaving cues at food sites and nest entrances, studies have not attempted to experimentally distinguish between cues and signals. Here, we examine the chemical composition of the scent marks left by the bumblebee Bombus terrestris at food sites and compare it to those found at a neutral location. If bees are depositing a cue, we expect the same chemicals to be found at both sites, but if they deposit a signal we only expect to find the scent marks at the food site. We were also interested in identifying the chemicals left at the nest entrance to determine if they differed from those used to mark food sites. We find that bees deposit the same chemicals at food, nest and neutral sites. Therefore, bumblebees leave behind general chemical footprints everywhere they walk and we propose that they learn to use these footprints in a manner that ultimately enhances their fitness, for example, to improve their foraging efficiency and locate their nest. Experimentally, distinguishing these two modes of information transfer is crucial for understanding how they interact to shape animal behaviour and what chemical bouquets are under natural selection. Handling Editor: Heikki Hokkanen     

Disentangling environmental and heritable nestmate recognition cues in a carpenter ant

Discriminating between group members and strangers is a key feature of social life. Nestmate recognition is very effective in social insects and is manifested by aggression and rejection of alien individuals, which are prohibited to enter the nest. Nestmate recognition is based on the quantitative variation in cuticular hydrocarbons, which can include heritable cues from the workers, as well as acquired cues from the environment or queen-derived cues. We tracked the profile of six colonies of the ant Camponotus aethiops for a year under homogeneous laboratory conditions. We performed chemical and behavioral analyses. We show that nestmate recognition was not impaired by constant environment, even though cuticular hydrocarbon profiles changed over time and were slightly converging among colonies. Linear hydrocarbons increased over time, especially in queenless colonies, but appeared to have weak diagnostic power between colonies. The presence of a queen had little influence on nestmate discrimination abilities. Our results suggest that heritable cues of workers are the dominant factor influencing nestmate discrimination in these carpenter ants and highlight the importance of colony kin structure for the evolution of eusociality.     

Effect of biologically active plants used as netst material and the derived benefit to starling nestlings

Summary The European starling Sturnus vulgaris preferentially incorporates fresh sprigs of particular plant species for use as nesting material. Chemicals found in these plants may act to reduce pathogen and ectoparasite populations normally found in nest environments. The present experiments were performed to test this Nest Protection Hypothesis. In the fild, we experimentally determined that wild carrot Daucus carota, a plant species preferred as nest material, effectively reduced the number of hematophagous mites found within nests relative to control nests without green vegetation. Chicks from nests containing wild carrot had higher levels of blood hemoglobin than chicks from control nests. However, there were no differences in weight or feather development. In the laboratory, we found that wild carrot and fleabane, Erigeron philadelphicus, (also preferred by starlings as nest material) substantially reduced the emergence of feeding instars of mites, while garlic mustard, Alliaria officinalis, (commonly available but not preferred) had little effect on the emergence of mites. We infer that preferred plant material may act to inhibit feeding or otherwise delay reproduction of mites, thereby reducing risk of anemia to developing nestlings.     

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.     

Persistent Intercolonial Trunkroute-marking in the African Weaver Ant Oecophylla longinoda Latreille (Hymenoptera,Formicidae): Tom Thumb's versus Ariadne's Orienting Strategies

The territorial African weaver ant Oecophylla longinoda forages in a 3-dimensional system when attending honeydew secreted by coccid colonies. The orienting strategy allowing workers to reach a static food resource was studied in laboratory conditions. Contrary to other studies devoted to territoriality in O. longinoda, our experiments show that, when moving off the nest, territorial faecal marking by the major workers is not randomly placed all over the home-range area. The chemical trail leading from the nest to a given food site is reinforced by faecal materials both on the horizontal and the vertical planes. In addition to visual cues and chemical trails laid by the major workers (Holldobler & Wilson 1978), foragers use the territorial marking both to localize the food site and to come back to the nest. Thus, anal-drop deposition in O. longinoda also has a clear dual-purpose function: territorial and orientationai marking. The ecological value of such a discrete Tom Thumb's orienting strategy enables workers to quickly reach a food location even after more than 5 months of inactivity on this given site. The persistent marked trail also has an intercolonial effect. This could allow the keeping of exploitation of a definite food site by alien colonies of the same species by reducing time costs for new exploring phases or for learning new spatial cues when foraging on an unknown environment.     

Nest Site Selection Influences Cinnamon Teal Nest Survival in Colorado

Nest survival of ducks is partially a function of the spatiotemporal characteristics of the site at which a bird chooses to nest. Nest survival is also a fundamental component of population growth in waterfowl but is relatively unstudied for cinnamon teal (Spatula cyanoptera). We investigated cinnamon teal nest survival in a managed wetland complex in southern Colorado, USA, and assessed nest site selection to determine whether nest site characteristics were adaptive. We monitored 85 nests in 2015–2017 on Monte Vista National Wildlife Refuge, Colorado and did not detect a difference in nest survival across years. Based on nest site selection data from 2017, cinnamon teal selected nest sites characterized by a lower proportion of forbs than available sites. The relationships between habitat characteristics and nest survival were variable. Microhabitat characteristics exhibited only weak effects on nest survival during the laying stage. Nest survival during incubation was negatively related to the proportion of forbs at the nest site and, to a lesser extent, the proportion of grasses. Nest site selection was predictive of future nest survival based on the percent of forbs and grasses around the nest site, suggesting teal select nest locations to benefit reproductive success. These results have the potential to guide local habitat management actions for breeding waterfowl. © 2020 The Wildlife Society.     

The role of volatiles in aggregation and host-seeking of the haematophagous poultry red mite <Emphasis Type="Italic">Dermanyssus gallinae</Emphasis> (Acari: Dermanyssidae)

Infestations with ectoparasitic poultry red mites (Dermanyssus gallinae) pose an increasing threat to poultry health and welfare. Because of resistance to acaricides and higher scrutiny of poultry products, alternative and environmentally safe management strategies are warranted. Therefore, we investigated how volatile cues shape the behavior of D. gallinae and how this knowledge may be exploited in the development of an attract-and-kill method to control mite populations. A Y-tube olfactometer bio-assay was used to evaluate choices of mites in response to cues related to conspecific mites as well as related to their chicken host. Both recently fed and starved mites showed a strong preference (84 and 85%, respectively) for volatiles from conspecific, fed mites as compared to a control stream of clean air. Mites were also significantly attracted to ‘aged feathers’ (that had remained in the litter for 3–4 days), but not to ‘fresh feathers’. Interestingly, an air stream containing 2.5% CO₂, which mimics the natural concentration in air exhaled by chickens, did attract fed mites, but inhibited the attraction of unfed mites towards volatiles from aged feathers. We conclude that both mite-related cues (aggregation pheromones) and host-related cues (kairomones) mediate the behavior of the poultry mite. We discuss the options to exploit this knowledge as the ‘attract’ component of attract-and-kill strategies for the control of D. gallinae.     

Wax on, wax off: nest soil facilitates indirect transfer of recognition cues between ant nestmates

Social animals use recognition cues to discriminate between group members and non-members. These recognition cues may be conceptualized as a label, which is compared to a neural representation of acceptable cue combinations termed the template. In ants and other social insects, the label consists of a waxy layer of colony-specific hydrocarbons on the body surface. Genetic and environmental differences between colony members may confound recognition and social cohesion, so many species perform behaviors that homogenize the odor label, such as mouth-to-mouth feeding and allogrooming. Here, we test for another mechanism of cue exchange: indirect transfer of cuticular hydrocarbons via the nest material. Using a combination of chemical analysis and behavioral experiments with Camponotus aethiops ants, we show that nest soil indirectly transfers hydrocarbons between ants and affects recognition behavior. We also found evidence that olfactory cues on the nest soil influence nestmate recognition, but this effect was not observed in all colonies. These results demonstrate that cuticular hydrocarbons deposited on the nest soil are important in creating uniformity in the odor label and may also contribute to the template.     

Choice of nest site protects army ant colonies from environmental extremes in tropical montane forest

Unlike most social insects, Eciton burchellii army ants cannot thermoregulate through nest construction. Instead, army ants thermoregulate behaviorally by creating a living nest (bivouac), shifting its position and structure, and potentially through nest site selection. We hypothesized that bivouac site selection is critical to E. burchellii colony survival. We predicted elevation above sea level, with associated variation in local abiotic environments, would affect bivouac site selection by E. burchellii colonies. We also expected nest sites to buffer against ambient variation in abiotic conditions. We recorded bivouac site choice by E. burchellii colonies at sites ranging from lowland wet forests to montane forests and reviewed previously published data. We measured microclimatic variables associated with nest sites in high-elevation montane forests: temperature, relative humidity, and light levels. Bivouac site selection varied with elevation: as elevation increased, fewer bivouac sites were exposed, more were underground, and fewer were elevated (in trees). High-elevation bivouac sites moderated diurnal temperature variation and had higher relative humidity levels and lower light levels than ambient conditions. The buffering of ambient temperature and humidity decreased with elevation in montane forests, suggesting that abiotic extremes in bivouac sites at the highest elevations may contribute to the upper elevational range limits of E. burchellii.     

Shoaling with infected conspecifics does not improve resistance to trematode infection

Group‐living animals can gain protection against parasitic infections through social contacts with previously infected conspecifics (social immunization). Recent research suggests that such protective effects can be induced through visual or chemical cues released by infected individuals, resulting in anticipatory immune upregulation among group members. Here, we study cue‐induced social resistance in rainbow trout Oncorhynchus mykiss exposed to a trematode parasite, the eye‐fluke Diplostomum pseudospathaceum. We established groups of naïve individuals (receivers) that were paired with previously infected individuals (donors) at different ratios of donors to receivers and at different time points since donor exposure to capture varying concentrations of the anticipated cues. While the pre‐infection elevated resistance among the donors, there was no evidence of social transfer of resistance, regardless of the ratio of donors and receivers in a group or the time since the pre‐infection. The results suggest that resistance through social signalling may be system‐specific and requires further study into the generality of the phenomenon as well as the nature of the cues involved.     

Association preference and mechanism of kin recognition in tadpoles of the toad <Emphasis Type="Italic">Bufo melanostictus</Emphasis>

In experiments with specially designed choice tanks, tadpoles of Bufo melanostictus spend significantly greater amounts of time near kin than near non-kin. However, in the absence of kin members, they prefer to spend more time near non-kin rather than stay away in isolation in the opposite blank zone with no company. This implies that association of toad tadpoles with their kin is due to attraction rather than repulsion from non-kin. Experiments designed to elucidate the sensory basis of kin recognition showed that toad tadpoles recognize their kin based on chemical cues rather than visual cues. They can also discriminate between homospecific non-kin and heterospecific (Sphaerotheca breviceps) tadpoles since the tadpoles spent significantly greater amounts of time near the former than near the latter. These findings suggest that where kin members are unavailable, selection may have favoured living with non-kin so as to derive benefits from group living and that a phenotype-matching mechanism may operate for both kin and species discrimination in B. melanostictus.     

Egg ejection cost can limit defence strategies against brood parasitism

A cost associated with the evolution of antiparasite strategies is the failure to recognize parasitic eggs, leading the host to evict its own eggs. However, there is evidence that birds recognize their own eggs through imprinting. This leads to the question of why birds accept parasitic eggs if such eggs can be identified. Here, we tested whether egg ejection per se can be costly due to increased predation risk to the remaining clutch and whether olfactory or visual cues of egg ejection increase predation. We carried out three field experiments to answer the following questions: (a) Does ejecting an egg increase nest predation risk? (b) Does the presence of olfactory cues, such as the smell of a broken egg, increase nest predation risk? And (c) Does the presence of visual cues, such as an egg shell below the nest, increase nest predation risk? We found evidence that egg ejection increases nest predation and that olfactory cues alone also increase nest predation. The presence of visual cues did not change predation rates. These data indicate that egg ejection is costly for both host and parasitic eggs that may remain in the nest. Our results suggest why host and parasite eggs are commonly found within the same nests, despite the possibility that hosts recognize and could possibly eject the parasite’s egg.     

How do goannas find sea turtle nests?

Squamate reptiles rely heavily on visual and chemical cues to detect their prey, so we expected yellow‐spotted goannas (Varanus panoptes) which are predators of sea turtle nests on mainland beaches in northern Australia would use these cues to find sea turtle nests. Ghost crabs (Ocypode ceratophthalmus and Ocypode cordimanus) are also common on Australian sea turtle nesting beaches and frequently burrow into sea turtle nests. However, the potential for ghost crab burrowing activity at sea turtle nests to signal the location of a nest to goannas has not been investigated. Here, we used camera traps and presence of tracks at nests to record goanna activity around selected nests during the incubation period and 10 days after hatchling turtles emerged from their nests. We also recorded the number of ghost crab burrows around nests to evaluate ghost crab activity. Our results indicated that nest discovery by goannas was independent of nest age, but that the nest visitation rate of goannas and crabs increased significantly after a nest had been opened by a goanna or after hatchlings had emerged from the nest. There was no apparent connection between ghost crab burrows into a nest and the likelihood of that nest being predated by goannas.     

Phoretic dispersal on bumblebees by bromeliad flower mites (Mesostigmata, Melicharidae)

Nectarivorous flower mites (Mesostigmata: Melicharidae) live mostly on hummingbird-pollinated plants in the New World. We observed Proctolaelaps sp. living on Neoregelia johannis (Bromeliaceae) in a coastal rain forest site in south-eastern Brazil. Flower anthesis of this bromeliad lasted a single day. We recorded mites moving into, feeding from, presumably mating and reproducing, and exiting bromeliad flowers within just a single day. We observed three ant species predating flower mites on bromeliads. The main visitor was the bumblebee Bombus morio, which always landed on the inflorescence to access nectar inside the bromeliad flowers. We found Proctolaelaps sp. mites on 47% of 38 bumblebees inspected, with each Bombus hosting 2 mites on average; only adults and mostly female mites (93%) usually found on the bumblebees’ gula region of the head. This is the first study to document nectarivorous flower mites living on a melittophilous host plant using bumblebees for phoretic dispersal.     

Experience Based Use of Landmark and Vector Based Orientation During Homing by the Ant Formica cunicularia (Hymenoptera: Formicidae)

Homing paths of Formica cunicularia foragers from an artificial food reward were analyzed on a familiar terrain and in displacement experiments on a familiar and an unfamiliar terrain. Foragers were tested either when relatively new to a foraging route (untrained group) or after a day’s experience with it (trained group). Untrained foragers followed direct homing paths to the nest site when tested in the familiar terrain but followed tortuous paths when displaced to the unfamiliar terrain. Trained foragers behaved similarly to untrained ones when tested from the food reward to the nest site in the familiar terrain but their behavior changed in displacements. Irrespective of the familiarity of the displacement site, these foragers followed paths taking them to the expected nest sites. The results showed that foragers did not rely on chemical cues for homing and revealed that untrained foragers disregarded path integration and were directed to the nest site when it is in their visual panorama. On the contrary, trained foragers may have relied on path integration on familiar and unfamiliar terrain. The results also demonstrated that experience greatly affected the preferential use of visual and vector based cues by foragers during homing.     

Sociality in a bark-dwelling huntsman spider from Australia,Delena cancerides Walckenaer (Araneae: Sparassidae)

Summary Social behavior is reported for the first time in a member of the family Sparassidae (Araneae), the Australian huntsman spiderDelena cancerides Walckenaer. Unlike any previously known social spider, this is a bark dwelling species and, thus, its sociality cannot have its basis on an aerial web, the structure that has been considered central to the evolution of sociality in other spider species. Colonies ofD. cancerides may comprise up to 300 individuals living in close physical contact under the exfoliating bark of deadAcacia, Callitris andCasuarina species. Specimens maintained in the laboratory feed communally and capture prey jointly. Although this intranest tolerance and communal feeding behavior is reminiscent of other highly social spiders,D. cancerides notably differs from these other species in the extreme aggression shown towards members of foreign colonies, its outbred population structure, and lack of sex ratio bias. We suggest that sociality in this species may have been facilitated by the presence of extended maternal care in the ancestral phylogenetic lineage, as suggested by the occurrence of such behavior in related nonsocial species, and that colonial living may have arisen as a consequence of the reduction and fragmentation ofDelena's habitat associated with the rise to dominance of the eucalypts. The apparent colony recognition observed may have evolved becauseDelena's hunting habits may require mechanisms to locate one's own colony after foraging expeditions and to exclude wandering outsiders from entering one's nest, in contrast to web-bound species that do not need to leave their nest to forage. How the observed outbreeding is accomplished in the face ofDelena's extreme intolerance to members of other nests, as well as how new colonies are formed, are issues that have yet to be investigated.     

Die Feinde der Raubmilben als Reduzierender Faktor der Spinnmilben

Summary The relations betweenMetatetranychus ulmi living on apple trees and its different predators are complex. The most important natural enemy of this spider mite is the predacious miteTyphlodromus pyri (= T. tiliae). It destroys more spider mites than the beneficial insects do. In the district of Stuttgart-Hohenheim about 38 species of insects and spiders feed onTyphlodromus mites. For instanceT. pyri is reduced considerably byOrius minutus. This bug is a natural enemy of aphids and spider mites, however it prefers the predatory mites. It attacks the spider mites and aphids only ifTyphlodromus mites are not available.Chrysopa vulgaris andAnthocoris nemorum are similar in their feeding habits. These two destroyTyphlodromus pyri also but they are less important thanO. minutus. The other beneficial insects in our orchards have little effect on spider mites or predacious mites. If we have enough pests on our apple trees to make spraying necessary, we should look forTyphlodromus mites and be careful no to destroy them. We should always examine the composition of the biocoenosis applying chemical agents because the populations of insects and predacious mites may vary from one area to the other.