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Alarm pheromones, which have been documented in many species of ants, are thought to elicit responses related to aggressive or defensive behaviour. The volatile odour 6‐methyl‐5‐hepten‐2‐one is described as an alarm pheromone in several species of ants, including the Australian meat ant, Iridomyrmex purpureus. The alarm pheromone is released by displaying workers that aggregate in the characteristic collective display grounds, located mid‐way between colonies or near contested food trees. Workers are typically more aggressive at the latter location, and the alarm pheromone may regulate the collective level of aggression. We investigated this possibility by exposing displaying workers to synthesised alarm pheromone 6‐methyl‐5‐hepten‐2‐one in a field experiment, and measuring their aggressive behaviour. We found no evidence that exposure to synthesised alarm pheromone caused changes in the aggressive level of workers. Subsequent field experiments revealed that the pheromone functions as an attractant, thereby increasing the density of displaying workers. More densely populated workers also display more aggressively, indicating that the interaction rate of displaying workers may determine the level of aggression in collective displays. This underlying mechanism can explain why displaying ants are more aggressive at the more densely populated food‐tree locations than those displaying at locations midway between two neighbouring colony nest sites. [ABSTRACT FROM AUTHOR]

Internally fertilized animals are characterized by the transfer of their spermatozoa during copulation. However, the duration of copulation is highly variable, which suggests that they may serve for other functions apart from spermatozoa transfer. For example, during copulation, males can stimulate the female by using genitalic movements and/or by positioning their spermatozoa adequately within the female genitalia. In the spider Holocnemus pluchei, males perform strong squeezes and torsion movements with their pedipalps (part of their genitalia actively related to copulation) inside the female genitalia and transfer their spermatozoa during Phase I of copulation. However, the exact moment in which such transfer occurs and its relation to the pedipalp movements are still unknown. Herein, we first have identified the precise moment when the spermatozoa transfer occurs during phase I and its relation to genital movements by interrupting mating couples at the beginning, at middle and at end of this phase. Subsequently, the spermatozoa number remaining in male genitalia and stored in female genitalia were counted. We detected no relation between the number of genital movements and the spermatozoa number present in both, female and male genitalia and body size. As stated above, male genital movements serve another role during copulation in addition to spermatozoa transfer in a context of post‐copulatory sexual selection; most likely, they stimulate the female in a cryptic female choice framework. [ABSTRACT FROM AUTHOR]

In many animal groups, sexually dimorphic ornaments are thought to evolve by intraspecific competition or mate choice. Some researchers pointed out that sexually monomorphic ornaments could also evolve by mate choice by both sexes or either sex. Many species of fruit fly have sexually monomorphic wing pigmentation. However, involvement of their sexually monomorphic ornaments in mate choice has not been tested. We aimed to examine whether the sexually monomorphic polka‐dotted pattern on wings of Drosophila guttifera contributes to mate choice. Because D. guttifera does not mate in the dark condition at all and no courtship sound has been observed, some visual information is likely to be used in mating behaviour. We compared the number of matings between individuals with and without wings and found that presence of wings influenced mating behaviour in both sexes. We then compared the number of matings between individuals bearing replaced wings, one group bearing conspecific D. guttifera wings and another group bearing heterospecific D. melanogaster wings with no pigmentation pattern. An effect of conspecific/heterospecific wings was only detected in mate choice by females. Comparison between wild‐type and black‐painted wings revealed no evidence of a contribution of wing pigmentation pattern to mate choice in either sex. [ABSTRACT FROM AUTHOR]

Many animals provide parental care to increase the success of offspring. Parental behaviors can be costly, and should only be directed toward related young. Offspring recognition and differential effort are ways that animals ensure that care is directed toward related individuals. Pardosa milvina is a small wolf spider that provides parental care for their young, carrying first their egg sac and later their spiderlings. This species is known to pick up abandoned egg sacs. We conducted a study to determine whether female P. milvina differentiated between her own egg sac and a conspecific's egg sac and whether there was a benefit to spiderlings in being raised by their biological mother, and whether age, when removed from the mother, influenced the outcome. In one experiment, we removed the egg sac from a female and gave her a choice of items to reattach: their own egg sac, another spider's egg sac, or a plastic bead. Females were more likely to pick up their own egg sac than another spider's. In another experiment, we removed a female spider's egg sac either 1 day or 7 days after the eggs were produced and gave them either their own egg sac or another spider's egg sac to care for. We measured hatching success and offspring survival. Spiders manipulated after 7 days were more likely to be abandoned as eggs, whether cared for by their biological mother, and reached adulthood less often. However, cross‐fostering had no effect on spiderling success whether the transfer occurred after 1 day. Our data showed that P. milvina can recognize their own egg sac, but there was no evidence of differential parental care provided to the biological offspring. [ABSTRACT FROM AUTHOR]

In many species, the location of females may affect the spatial distribution of males. If females vary in their reproductive quality, and males have to fight for access to the females, then weaker males should aggregate around high‐quality females while avoiding areas occupied by males of high fighting capacity. However, this aggregation pattern should only occur if males have low dispersing costs. Otherwise, males should preferentially stay near the first female they encounter. In this study, we used the golden silk orb‐web spider, Trichonephila clavipes, to evaluate the following hypotheses: When costs of moving between female webs are low, weaker males should aggregate at the periphery of (a) webs of females that have higher reproductive quality and (b) webs of females occupied by central males (i.e., stronger males that are guarding females in the central web position) with lower fighting capacity. To evaluate these hypotheses, we counted the number of males at the periphery of female webs that were aggregated with other female webs (i.e., areas with lower dispersal costs among webs) or isolated from other female webs (areas with higher dispersal costs among webs). We used the ontogenetic status of the females (mature or immature) as a surrogate of female reproductive quality and the length of the first pair of male legs as a surrogate of male fighting capacity. We found that, independently of the spatial disposition of female webs, the number of males per web was unrelated to female reproductive quality or the fighting capacity of the central males. We conclude that this pattern provides an intriguing system in which the intensity of intra‐sexual competition for males presumably varies in unpredictable ways between different female webs. [ABSTRACT FROM AUTHOR]

Nest‐site selection is a crucial decision made by parents because inadequate sites may expose the offspring and the parent to harsh abiotic and biotic conditions. Although nest‐site selection has been reported for some species of arthropods, the proximate cues used by parents to select the nest site and the adaptive meaning of nest‐site selection are still poorly understood. We investigated nest‐site selection in the harvestman Quindina limbata, in which males build mud nests on the surface of fallen logs and perform parental care. This species inhabits tropical forests where rainfall destroys nearly 50% of the nests, representing an important selective force shaping nest‐site selection. We followed 139 nests and recorded the position (angle) where these nests were located on the fallen log surface. Males showed a complex pattern of nest‐site selection that responded to three proximate cues: the direct impact of raindrops on the upper half of the fallen log, the drag force caused by flowing water on the laterals of the fallen log, and water saturation on the lowest part of the fallen log. These selective pressures created a bimodal pattern of nest distribution on the lower half of the fallen logs. The peaks of this distribution occurred in places where nests are protected from the direct impact of raindrops, the drag force caused by flowing water is not high, and the risk of nest flooding is low. The possible adaptive meaning of nest‐site selection is to minimize the risk of nest destruction, which imposes energetic costs to males that need to build another nest. Nest‐site selection may also minimize reproductive costs because males with damaged nests show decreased attractiveness to females. Finally, nest‐site selection may increase offspring fitness minimizing the risk of egg mortality associated with nest destruction and anoxia when nests are flooded. [ABSTRACT FROM AUTHOR]

Animals communicate using a diversity of signals produced by a wide array of physical structures. Determining how a signal is produced provides key insights into signal evolution. Here, we examine a complex vibratory mating display produced by male Schizocosa floridana wolf spiders. This display contains three discrete substrate‐borne acoustic components (known as "thumps", "taps", and "chirps"), each of which is anecdotally associated with the movement of a different body part (the pedipalps, legs, and abdomen respectively). In order to determine the method of production, we employ a combination of high‐speed video/audio recordings and SEM imaging of possible sound‐producing structures. Previous work has suggested that the "chirp" component is tonal, a signal trait that would be potentially unique in the genus. We measured signal tonality for all courtship components, as well as for courtship components from sixteen other Schizocosa wolf spiders. Our results suggest that S. floridana produces courtship song using a combination of shared (palpal stridulation and foreleg percussion) and novel (abdominal movement) sound production mechanisms. Of particular interest, the "chirp", which is produced using a novel abdominal production mechanism, is the only known tonal signal with acoustic properties that are unique within the genus. We argue that the potential evolution of a novel sound production mechanism has opened up a new axis of signaling trait space in this species, with important implications for how this signal is likely to function and evolve. [ABSTRACT FROM AUTHOR]

Life history theory predicts that iteroparous animals adaptively partition reproductive effort between current and future reproduction. When rearing costs of current offspring exceed the potential benefits, parental care should be terminated and deferred toward future reproduction. We tested two related predictions that follow from life history theory: (a) parents should be sensitive to offspring viability and withhold parental care if offspring survival probability drops and future reproductive opportunities are likely, and (b) parents should be less sensitive to offspring survival probability when future reproduction is unlikely and maximize parental care late in life. The wolf spider, Pardosa milvina, demonstrates extensive parental care; however, they may also abandon or cannibalize their egg sacs. We tested the effects of egg sac damage and production of a previous egg sac on egg sac abandonment and cannibalism decisions. Among four egg sac groups (1st egg sac intact, 1st egg sac damaged, 2nd egg sac intact, 2nd egg sac damaged), we daily monitored egg sac abandonment and cannibalism and measured differences in egg sac searching, protection, and grooming among removed and damaged egg sacs (N = 116 with 1st egg sac and 88 with 2nd egg sac). Females with first egg sacs abandoned and cannibalized damaged egg sacs significantly more compared to unmanipulated egg sacs; however, females with second egg sacs were insensitive to egg sac damage. Females also spent significantly more time protecting second egg sacs compared to first egg sacs and groomed damaged egg sacs significantly more than undamaged. These results support the general predictions of life history theory that indicate that abandonment and cannibalism should decrease with diminished future reproductive potential and that parents should be less sensitive to indicators of offspring survival probability late in life. [ABSTRACT FROM AUTHOR]

Residency is an important predictor of success in contests with ownership asymmetries. Residency often can interact with a winning experience. However, given that some residents lose a contest even when showing an ownership advantage and that the process leading to loss often determines the loser's subsequent success, prior ownership might also interact with a loss. Here, we staged experimental contests between males of the hermit crab Pagurus minutus with a similar‐sized weapon (i.e., cheliped) to examine this possibility. Male–male contests in this species occur between a solitary intruder and an owner guarding a mature female. We evaluated (a) whether resource ownership and female value affect the contest outcome and (b) whether the probability of winning after losing differs depending on the initial role of the loser (i.e., owner or intruder) by using precopulatory guarding pairs of P. minutus collected from the field. In the first fighting trial, we found an ownership advantage and increasing owner success as the body size of his partner increased. Although some owners lost the fight, in contrast to our prediction, the frequency of losing in the second fighting trial did not differ between prior owners and prior intruders. Because losers from the first fighting trial of male–male contests have no female regardless of their initial role, this shared solitary status might be related to the lack of difference in success in the second fighting trial. Moreover, unlike in other animals, resident status might not always assure greater fighting ability in P. minutus males because guarding Pagurus males can avoid male–male contests by climbing up objects in the field. Losers in the first trial, therefore, may have been weaker contestants based on traits other than size, regardless of whether they were owners or intruders. [ABSTRACT FROM AUTHOR]

Among all activities displayed by ant colonies, searching for food is essential for all individuals survival. However, many external activities are hazardous or restrictive for the entire society. Even though leaf‐cutter ants are highly successful insects, they are subject to extreme aspects of foraging, as raindrops and wind. Although recruitment and food exploitation are known to change with temperature and humidity, barometric pressure changes and how they affect ant behavior remain unknown. We aimed to determine how an increase or decrease in barometric pressure might modify foraging strategies of the leaf‐cutter ant Atta sexdens compared to steady pressure. The first modification observed in the workers behavior was the scouts greater promptness in leaving the nest when the barometric pressure decreased. Regard to the foragers, there was no difference in the number of individuals recruited for collecting leaves. However, it was cut and brought into the nest 1.5 and 2 times more leaves during the pressure drop, respectively. The reason for this foraging efficiency as a whole was ultimately the sum of the efficiency of each forager. The shifts in behavior, therefore, could be related to the indirect consequences of a pressure decrease, such as rainfall and strong winds, both strong constraints on ants on a trail. This is the first report of barometric pressure affecting the behavior of a social insect under controlled conditions. [ABSTRACT FROM AUTHOR]

A spider's web is an extended phenotype and a direct product of behavior. Variation in web architecture may be the result of individual differences in genotype, environment, or experience. We analyzed variation in the web architecture of western black widow spiders, Latrodectus hesperus, by testing two hypotheses: (a) intrinsic individual differences and (b) plasticity according to experience of the site of prey capture. We used treatments manipulating the site of prey capture experienced by the spiders: sheet only, gum‐footed lines only, and alternating patterns between sheet and gum‐footed lines equally. We found considerable consistent individual variation (repeatability of r =.56) in one web component (gum‐footed lines) and negligible plasticity in either component. We discuss our results in terms of the potential for the design of these web components to respond to selection, and of potential additional causes of variation in extended phenotypes. [ABSTRACT FROM AUTHOR]

Conspicuous colouration increases male reproductive success through female preferences and/or male–male competition. Despite the advantages of conspicuous colouration, inconspicuous male morphs can exist simultaneously in a population due to genetic diversity, condition dependence or developmental constraints. We are interested in explaining the male dichromatism in Xanthagrion erythroneurum damselflies. We reared these damselflies in outdoor insectaries under natural conditions and showed that this species undergoes ontogenetic colour changes. The younger males are yellow and change colour to red 6–7 days after their emergence. We took red and yellow male reflectance spectra and found that red males are brighter than yellow males. Next, we aimed to determine whether ontogenetic colour change signals sexual maturity with field observations and laboratory experiments. Our field observational data showed that red males are in higher abundance in the breeding territory, and they have a higher mating frequency than yellow males. We confirmed these field observations by enclosing a red and a yellow male with two females and found that yellow males do not mate in presence of red males. To determine whether colour change signals sexual maturity, we measured mating success of males before and after colour changes by enclosing a single male at different age (day 3‐day 7) and colour (yellow, intermediate and red) with a single female in a mating cage. Males did not mate when yellow but the same male mated after it changed colour to red, suggesting the ontogenetic colour change signals sexual maturity in this species. Our study shows that male dichromatism can be age‐dependent and ontogenetic colour change can signal age and sexual readiness in non‐territorial insects. [ABSTRACT FROM AUTHOR]

Nests of the primitively eusocial orchid bee Euglossa viridissima are generally founded by a solitary female but can be reactivated by female offspring, in the presence or absence of the mother. The population therefore exists of solitary and social nests that co‐occur in an area. A female can stay as a subordinate helper under a dominant female or disperse to become a solitary foundress. Yet, the costs and benefits of the different social phenotypes are so far little understood. Here, we compared solitary and social nests of orchid bees. We used offspring of solitary and social nests to calculate offspring sex ratio, and applied molecular markers to calculate intranidal relatedness, infer maternity and test whether sociality may have a genetic component. We found that social nests had on average more brood than solitary nests. The overall sex ratio in the population did not differ from 1:1. However, social nests tended to produce a split sex ratio with some nests producing mainly males and others mainly female offspring. Regardless of social phenotype, the number of offspring was correlated with the sex ratio, with smaller nests having a more female‐biased offspring. In social nests, not all offspring resulted from a single‐mated mother, which was also the case for some solitary nests. This suggests shared reproduction in social nests and may be an indication that intraspecific parasitism and nest takeover are not uncommon. Structure analyses did not reveal different genetic background of the two social phenotypes. Our results suggest that there is no clear benefit that favours one of the two social phenotypes over the other and that the population is kept at balance in terms of sex ratio. [ABSTRACT FROM AUTHOR]

Sexual dichromatism is widespread among animals, but examples of "reverse" sexual dichromatism, in which females are more brightly colored than males, are extremely rare. We discovered a unique case of reverse sexual dichromatism in the golden rocket frog (Anomaloglossus beebei), a diurnal Neotropical frog. Females are bright "golden" in color, and males are drab tan with brown pigmentation that darkens when they are calling. Here, we document this color variation with calibrated digital photography and further show that there is no evidence for sex‐specific habitat matching; both sexes live in the same well‐lit habitat on green bromeliad leaves. Our results suggest that color variation in this species is an intraspecific signal and provide an important exception to the general expectation that males are more visually conspicuous in species with conventional sex roles. [ABSTRACT FROM AUTHOR]

Recent wins and losses can inform individuals about their relative fighting abilities and modify their subsequent contest decisions. Using a mangrove rivulus, Kryptolebias marmoratus, we tested the hypothesis that visual and limited physical interactions can also convey information and modify subsequent contest decisions. Individuals were exposed to a stronger or weaker conspecific through a glass or a mesh partition before a contest with a size‐matched naïve opponent. Individuals were expected to (a) assess themselves to have worse/better fighting ability and behave less/more aggressively after having interacted with a stronger/weaker conspecific and (b) display different degrees of behavioural modifications for the two partition treatments (mesh‐partition > glass‐partition). The results showed that interactions with a stronger/weaker conspecific through a glass partition did not have a strong effect on the fish's subsequent contest behaviour. Restricted physical interaction with a stronger/weaker conspecific through a mesh partition, however, had an unexpected effect, causing individuals to behave more/less aggressively (matching the behaviour of the conspecifics) and/or win more/fewer subsequent contests. These results indicate that contest resolution is important for the fish to exhibit the loser–winner effects (i.e. behaving less/more aggressively after having lost/won against a stronger/weaker conspecific) detected in previous studies of the fish. We propose and discuss the possibility that the "behavioural matching" of the mesh‐partition treatment results from unresolved physical interactions with a stronger/weaker conspecific causing the individuals to either anticipate stronger/weaker opponents in subsequent competitions or assess themselves to be an equally good/bad fighter as the conspecific. The results of previous studies and the present study of the fish show that pre‐exposing an individual to the same type of conspecifics could elicit diverse, sometimes opposite, behavioural responses depending on how the individual is permitted to interact with the conspecific. [ABSTRACT FROM AUTHOR]

In insects, death‐feigning is an effective defence strategy. Eucryptorrhynchus brandti, a major borer pest in China, has a weak flight ability and exhibits obvious death‐feigning behaviour when disturbed. Despite a large number of studies of its biological and ecological properties as well as control methods, the death‐feigning behaviour has not been specifically described. In laboratory conditions, we recorded the survival rate under starvation and feeding conditions and evaluated the effect of starvation on the duration and occurrence of death‐feigning. In a continuous experiment, we examined variation in the death‐feigning duration every day over 7 day. Then, we evaluated the effects of starvation for 3, 6 and 9 day in a non‐continuous experiment and further observed variation in the death‐feigning intensity. We found that starvation significantly affected the survival rate. Survival time was significantly longer in the starvation group than in the feeding group, and females had longer survival times than males (female: 14 day, male: 8 day). In the continuous experiment, starved E. brandti had the longest duration of death‐feigning at 2 day, followed by a significant decrease. In the non‐continuous experiment, the duration and proportion of death‐feigning decreased significantly as the duration of starvation increased and were significantly lower than feeding. These observations suggest that starvation is a non‐negligible factor in the death‐feigning behaviour of E. brandti adults, facilitating the interpretation of future ecological and behavioural data of thanatosis. [ABSTRACT FROM AUTHOR]

Examines the prey capture behavior of the orb-web spider. Effects of the feeding history on the web structure; Profitability of the prey types; Types of prey.

The exact moment when a male of spider Trichonephila clavipes inserts his pedipalp into the female epigynum, and consequently begins to mate. Photograph was taken in Belo Horizonte, Brazil. Males of the golden silk orb-web spider trichonephila clavipes do not aggregate in webs of high-quality females by Joao Gabriel Lacerda de Almeida and Paulo Enrique Cardoso Peixoto. https://doi.org/10.1111/eth.13132 GLO:EUB/01apr21:eth13050-toc-0001.jpg PHOTO (COLOR): . gl. [Extracted from the article]