Solitary Females Research Articles

Nest protection and foraging behaviour in solitary and social nests of the socially polymorphic orchid bee Euglossa viridissima

AbstractNatural enemies impose a selective pressure on solitary insects that may favour the evolution of sociality. In the socially polymorphic orchid bee Euglossa viridissima, females found nests solitarily and provision a first batch of brood. After brood maturity, a nest can remain solitary (all offspring disperse) or become social, when one or more subordinate daughters forage for nesting material and brood provisions for the dominant mother. Solitary females leave their nest unguarded when foraging whilst a female in a social nest can guard the nest while nestmates are foraging. By observing solitary and social nests, we found that subordinate foragers in social nests undertook longer provisioning trips than solitary females. The presence of a guarding female in a social nest protected the nest against intrusion, possibly favouring longer provisioning trips. Moreover, the frequency of successful attempts by intruders to enter nests was significantly lower in social nests. Our results provide strong support for the parasite defence hypothesis for the evolution of social behaviour.

Effects of past mating behavior versus past ejaculation on male mate choice and male attractiveness.

Past reproductive effort allows males to assess their ability to acquire mates, but it also consumes resources that can reduce their future competitive ability. Few studies have examined how a male's reproductive history affects his subsequent mate choice, and, to date, no study has determined the relative contribution of past mating behavior and past ejaculate production because these two forms of investment are naturally highly correlated. Here, we disentangled the relative effects of past mating behavior and past ejaculate production in mosquitofish (Gambusia holbrooki) by experimentally preventing some males from ejaculating when trying to mate. We assessed the effect of mating behavior on mate choice by comparing males that had previously been with or without access to females and male rivals for 8 and 16 weeks and assessed the effect of ejaculation on mate choice by comparing males that either could or could not ejaculate when they had access to females for 16 weeks. Reproductive treatment did not affect male attractiveness, but it did affect male mate choice. Somewhat surprisingly, in five of the six treatment-by-age at testing combinations, males preferred a female in the vicinity of a male rival over a solitary female. This preference was marginally stronger for males that had previously engaged in mating behavior but were unaffected by past ejaculate production. We discuss the potential benefits to males of associating with another male when seeking mates. This is the first study to quantify the relative influence of pre- and post-copulatory reproductive investment on male mate choice.

Large fitness benefits of social nesting in a small carpenter bee

Abstract Facultatively social insects are an optimal model group for the study of the emergence of cooperation between individuals. Factors influencing the fitness benefits of social nesting are still debated. Nonreproductive subordinates can benefit from indirect fitness benefits due to increasing reproductive success of related individuals or direct fitness benefits due to direct future reproduction. Here, we studied the costs and benefits of social nesting in the small carpenter bee Ceratina albosticta. From demographic data and within-nest relatedness, we obtained key parameters for assessing the fitness of solitary females, social primaries, and social secondaries. C. albosticta were found to usually mate with one male and multiple mating is not common although exists at low frequencies. Social nests usually contain two females, which were found to be related (full sisters), but also some females were unrelated to each other. Patterns of parentage from microsatellite loci revealed that only one female reproduces in social nests. Our results show that relatedness, per capita brood productivity, and offspring survival strongly increase the fitness benefits of social nesting strategies. Social secondaries, when related to the social primaries, have higher inclusive fitness than solitary females, but unrelated social nesting females had no indirect fitness and much reduced inclusive fitness compared to solitary females. Interestingly, average fitness benefits of the social secondary were higher than solitary females. This study provides important empirical data on the costs and benefits of sociality in a facultatively social bee and sets the stage for future comparative studies.

Social divergence: molecular pathways underlying castes and longevity in a facultatively eusocial small carpenter bee.

Unravelling the evolutionary origins of eusocial life is a longstanding endeavour in the field of evolutionary-developmental biology. Descended from solitary ancestors, eusocial insects such as honeybees have evolved ontogenetic division of labour in which short-lived workers perform age-associated tasks, while a long-lived queen produces brood. It is hypothesized that (i) eusocial caste systems evolved through the co-option of deeply conserved genes and (ii) longevity may be tied to oxidative damage mitigation capacity. To date, however, these hypotheses have been examined primarily among only obligately eusocial corbiculate bees. We present brain transcriptomic data from a Japanese small carpenter bee, Ceratina japonica (Apidae: Xylocopinae), which demonstrates both solitary and eusocial nesting in sympatry and lives 2 or more years in the wild. Our dataset captures gene expression patterns underlying first- and second-year solitary females, queens and workers, providing an unprecedented opportunity to explore the molecular mechanisms underlying caste-antecedent phenotypes in a long-lived and facultatively eusocial bee. We find that C. japonica's queens and workers are underpinned by divergent gene regulatory pathways, involving many differentially expressed genes well-conserved among other primitively eusocial bee lineages. We also find support for oxidative damage reduction as a proximate mechanism of longevity in C. japonica.

Aggregation pheromone 4-vinylanisole promotes the synchrony of sexual maturation in female locusts.

Reproductive synchrony generally occurs in various group-living animals. However, the underlying mechanisms remain largely unexplored. The migratory locust, Locusta migratoria, a worldwide agricultural pest species, displays synchronous maturation and oviposition when forms huge swarm. The reproductive synchrony among group members is critical for the maintenance of locust swarms and population density of next generation. Here, we showed that gregarious female locusts displayed more synchronous sexual maturation and oviposition than solitarious females and olfactory deficiency mutants. Only the presence of gregarious male adults can stimulate sexual maturation synchrony of female adults. Of the volatiles emitted abundantly by gregarious male adults, the aggregation pheromone, 4-vinylanisole, was identified to play key role in inducing female sexual maturation synchrony. This maturation-accelerating effect of 4-vinylanisole disappeared in the females of Or35-/- lines, the mutants of 4-vinylanisole receptor. Interestingly, 4-vinylanisole displayed a time window action by which mainly accelerates oocyte maturation of young females aged at middle developmental stages (3-4 days post adult eclosion). We further revealed that juvenile hormone/vitellogenin pathway mediated female sexual maturation triggered by 4-vinylanisole. Our results highlight a 'catch-up' strategy by which gregarious females synchronize their oocyte maturation and oviposition by time-dependent endocrinal response to 4-vinylanisole, and provide insight into reproductive synchrony induced by olfactory signal released by heterosexual conspecifics in a given group.

Polar bear (Ursus maritimus) use of the Cape Bathurst polynya and flaw lead

The Cape Bathurst polynya and flaw lead (CBP) are major, predictable habitat features with ≤15% ice cover in an otherwise ice-covered Beaufort Sea, and thought to provide hunting opportunities for polar bears (Ursus maritimus Phipps, 1774). We assessed 78 adult (female; with and without cubs) and subadult (male and female) polar bears’ use of the CBP from October to June 2007–2014. The CBP was up to 725 km wide in autumn, ice-covered in winter, and <306 km wide in spring. Seventy-nine percent (n = 62) of the bears used the CBP (≥1 location <2.4 km, or one 4 h step length, from the CBP). Use was higher for solitary adult females and subadult males, which travelled faster with low turning angles along wider sections than females with offspring and subadult females. Bears were closest to the CBP during the spring hyperphagia season. Although a wider CBP did not prevent crossing, bears primarily crossed from the coast towards pack ice at locations 53% narrower than areas not crossed. Bears might avoid crossing when it would require a long-distance swim. The CBP affects polar bear ecology by providing hunting habitat and a corridor that could increase prey encounters but may affect movement.

Seasonal and diel movement patterns of brown bears in a population in southeastern Europe.

Most animals concentrate their movement into certain hours of the day depending on drivers such as photoperiod, ambient temperature, inter‐ or intraspecific competition, and predation risk. The main activity periods of many mammal species, especially in human‐dominated landscapes, are commonly set at dusk, dawn, and during nighttime hours. Large carnivores, such as brown bears, often display great flexibility in diel movement patterns throughout their range, and even within populations, striking between individual differences in movement have been demonstrated. Here, we evaluated how seasonality and reproductive class affected diel movement patterns of brown bears of the Dinaric‐Pindos and Carpathian bear populations in Serbia. We analyzed the movement distances and general probability of movement of 13 brown bears (8 males and 5 females) equipped with GPS collars and monitored over 1–3 years. Our analyses revealed that movement distances and probability of bear movement differed between seasons (mating versus hyperphagia) and reproductive classes. Adult males, solitary females, and subadult males showed a crepuscular movement pattern. Compared with other reproductive classes, females with offspring were moving significantly less during crepuscular hours and during the night, particularly during the mating season, suggesting temporal niche partitioning among different reproductive classes. Adult males, solitary females, and in particular subadult males traveled greater hourly distances during the mating season in May‐June than the hyperphagia in July–October. Subadult males significantly decreased their movement from the mating season to hyperphagia, whereas females with offspring exhibited an opposite pattern with almost doubling their movement from the mating to hyperphagia season. Our results provide insights into how seasonality and reproductive class drive intrapopulation differences in movement distances and probability of movement in a recovering, to date little studied, brown bear population in southeastern Europe.

Size, age, and social control of protogynous sex change in the labrid fish Pteragogus aurigarius

The labrid fish Pteragogus aurigarius undergoes protogynous (female-to-male) sex change, with dichromatic and dimorphic differences in sexes. Similar to some other protogynous fishes, this species is polygynous. We report the size and age at which sex change occurs by monthly sampling fishes at Tateyama, central Japan, from 2011 to 2012, and investigate conditions of sex change in rearing experiments from 2013 to 2015. Sexual phases are determined using gonad histology, and ages by otolith analysis. Of 231 sampled specimens, 99 were female, 129 were male, and three were intersexual. Of males, 86 resembled typical males, and are referred to as “normal males (NM)”, and 43 resembled females in color, which we refer to as “males with female appearance (MFA)”. NM sizes exceeded those of female, intersexual and MFA individuals. Because intersexual and MFA individuals did not differ in color or size, they may have recently transitioned to being male. Intersexual and MFA individuals ranged 85–135 mm in total length and 1–3 years in age, and appeared from September to March. Because the spawning season runs from June to September, sex change must occur afterwards. Sex change occurred in solitary females, and larger females held with other females in aquaria, both with and without aquarium partitions. Size hierarchy in social groups may be important for sex change of the largest female to male regardless of the number of individuals present.

Dining from the coast to the summit: Salmon and pine nuts determine the summer body condition of female brown bears on the Shiretoko Peninsula.

Body condition in mammals fluctuates depending on energy intake and expenditure. For brown bears (Ursus arctos), high‐protein foods facilitate efficient mass gain, while lipids and carbohydrates play important roles in adjusting dietary protein content to optimal levels to maximize energy intake. On the Shiretoko Peninsula, Hokkaido, Japan, brown bears have seasonal access to high‐lipid pine nuts and high‐protein salmon. To assess seasonal and annual fluctuation in the body condition of adult female brown bears in relation to diet and reproductive status, we conducted a longitudinal study in a special wildlife protection area on the Shiretoko Peninsula during 2012–2018. First, analyses of 2,079 bear scats revealed that pine nuts accounted for 39.8% of energy intake in August and salmon accounted for 46.1% in September and that their consumption by bears varied annually. Second, we calculated the ratio of torso height to torso length as an index of body condition from 1,226 photographs of 12 adult females. Results indicated that body condition continued to decline until late August and started to increase in September when salmon consumption increased. In addition, body condition began to recover earlier in years when consumption of both pine nuts and salmon was high. Furthermore, females with offspring had poorer body condition than solitary females, in particular in late August in years with low salmon consumption. Our findings suggest that coastal and subalpine foods, which are unique to the Shiretoko Peninsula, determine the summer body condition of female brown bears, as well as their survival and reproductive success.

Reproductive behavior of Spix’s Whiptails in the wild: understanding the costs and benefits of mate-guarding

Across animal taxa, females of non-territorial species have potential opportunities to mate with multiple partners; hence, the primary mechanism available for males to ensure paternity is to guard the receptive female after copulation and repel other males. Hypothetically, mate-guarding is costly for males in terms of energy acquisition and increased risk of injury, and beneficial for females in terms of decreased harassment by other males and an increase in available foraging time. Here, we provide a detailed description of mating behavior and test these hypotheses in the Spix’s Whiptail (Ameivula ocellifera). Mating behavior is characterized by the following events: (1) a male courts a female in the entrance of her burrow; (2) if courtship is accepted by the female, a consensual copulation occurs; (3) after copulation the male accompanies the female during her daily activity, being aggressive towards other males; (4) when the female returns to the burrow, the companion male remains vigilant at the entrance and repels rival males. Besides the mate-guarding strategy, alternative mating tactics are adopted by some males that do not guard females after courtship and consensual copulation, while others try to copulate opportunistically with a female without prior courtship. Companion males spent more time vigilant, less time actively foraging, and captured less prey when compared to solitary males. Accompanied females captured prey in a similar proportion to solitary females but spent more time vigilant and less time foraging. Companion males won 100% of their interactions with rival males, chasing them away from the females. Accompanied females hence did not suffer harassment from other males when companion males were close. Our results evidence energetic costs of mate-guarding for males but not increased risk of injuries. By accepting mate-guarding, females do not appear to have energetic gains and lose the advantage of cryptic mate choice but can benefit from access to high-quality males and protection from harassment.

Glucocorticoid levels predict subsequent social tactic in females of a facultatively social mammal

Abstract Facultatively social species, in which individuals can switch between group‐ and solitary‐living tactics, offer an opportunity to shed light on proximate mechanisms underlying alternative life histories. Promising hormonal mediators of social tactic include glucocorticoids, which control energy allocation and are negatively related to body condition, and testosterone which regulates numerous social behaviours. Here, we investigated hormone profiles associated with social tactic in eight generations of free‐living female striped mice Rhabdomys pumilio. Females are group living during the non‐breeding season but live solitarily or with female kin in communally breeding groups during the breeding season. We tested whether females' baseline levels of corticosterone (a glucocorticoid) and testosterone measured during the breeding season differed before and after females left the group (i.e. when they switched from a group living to solitary social tactic), and whether the hormone levels of females that remained group living differed before and after their nestmates became solitary. We also asked whether seasonal variation in hormone levels was associated with social tactic. During the breeding season, corticosterone levels were lower in solitary than group‐living females both before and after solitary females left the group, and did not differ in solitary females before and after leaving. In group‐living females, corticosterone was higher after their nestmates became solitary than before they left. Testosterone levels did not differ before and after females became solitary and were not associated with social tactic. Corticosterone was higher during the breeding than the non‐breeding season in group‐living females but did not differ between the seasons in solitary females. Testosterone levels were higher in both social tactics during the non‐breeding season. We conclude that baseline corticosterone but not testosterone levels are associated with female social tactic, and that corticosterone levels at the start of the breeding season, when all females are group living, may be an indicator of subsequent tactic: solitary females' corticosterone levels were lower than those of females that remained group living even before the solitary phenotype was expressed. Glucocorticoids might therefore play a modulatory role in social organisation in facultatively social species. A free Plain Language Summary can be found within the Supporting Information of this article.

Climbing behavior of guarding males in the hermit crab Pagurus minutus: the effect of rivals, female size, and being weaponless

Male crustaceans engage in precopulatory mate-guarding to monopolize a female. However, a conspecific rival often takes the female from the guarding males during male–male contests, so guarding males should invest in behavior to decrease the rate of encounters with rivals, especially when they are potentially weak and guard a valuable female. We examined this idea using a net-climbing (avoidance) response by precopulatory guarding males of the hermit crab Pagurus minutus. Guarding males more often climb revetment walls in the field than solitary males and females, and the guarders were larger in body size than the solitary males on the walls. Guarding males increased climbing effort in the presence of rivals compared to controls (no stimulus), but not when faced with a non-threat organism. Compared to intact guarding males, those without a major cheliped (“weaponless”) were less likely to succeed in defending their partner in direct fights, but increased climbing investment overall, rather than especially when a rival was present. Although female size positively correlates with clutch size in this species, male climbing height decreased with increasing size of the guarded female. We discuss the effectiveness and importance of climbing in this species as it relates to conditions at our study site and the general vulnerability of guarding males depending on weapon status.

Activity patterns in the reintroduced Pyrenean brown bear population

Mammals usually adjust behavioral patterns when exposed to disturbances. Elusiveness and low-risk time selection may reduce their stress in periods of highest risk. In Europe, brown bears (Ursus arctos) coexist with humans in densely populated and modified landscapes and, consequently, are exposed to human-caused disturbances during the daytime hours. Furthermore, intraspecific interactions might also influence their behavioral responses, especially during the mating season. Activity patterns of several large carnivores have been thoroughly studied; however, research is scarce for relocated populations. Here, we report the activity patterns in the reintroduced brown bear population in the Pyrenees. We expected the bears to reduce their activity depending on the type and level of disturbances. We analyzed individual behavior of both sexes (males, solitary females, and females with offspring) and age groups (adults and subadults) using camera-trap surveys under different types of intraspecific and anthropogenic disturbances. In general, bears were more active during the night (2200–0600 h) and avoided peaks of human activity (1000–1800 h). Furthermore, with the increasing nocturnal disturbance of adult males during the mating season, females with offspring and subadults were more active during daylight. This suggests that vulnerable individuals showed high tolerance for human presence. These results contribute to improve our knowledge of how a threatened and relocated bear population behaves in a human-modified landscape of southern Europe. Further research on this population will be crucial to establish optimal management interventions during translocations, and the prevention of human-bear encounters and conflicts.

Leave me alone: solitary females attract more mates in a nocturnal insect

AbstractSpatial distributions of sexual competitors and potential mating partners have a large impact on sexual selection and mating systems. Typically, such effects are investigated with regard to male aggregations. However, females may also need to compete for mating opportunities. Here, we investigated the consequences of clustering and rival attractiveness on female mate attraction success under field conditions in a nocturnal beetle, the common glowworm, Lampyrus noctiluca. We placed dummy females of two glow intensity (attractiveness) levels either alone or in clusters of varying attractiveness compositions. We found that, by displaying alone rather than in a cluster, females have a higher probability of mating and greater potential to exercise mate choice. Within clusters, females of both attractiveness levels had the highest probability of mating when having neighbors of only the less attractive type. These results show that both the presence and attractiveness of rivals can strongly influence females’ mate attraction. The findings also suggest that the typical distribution of glowing females in the wild is better explained by female than male benefits. Hence, the results highlight the important links between spatial distribution of females, male mate searching, and sexual selection.

Dynamics of bacterial composition in the locust reproductive tract are affected by the density-dependent phase.

The important role that locust gut bacteria play in their host biology is well accepted. Among other roles, gut bacteria are suggested to be involved in the locust swarming phenomenon. In addition, in many insect orders, the reproductive system is reported to serve as a vector for trans-generation bacterial inoculation. Knowledge of the bacterial composition of the locust reproductive tract is, however, practically absent. Here we characterized the reproductive system bacterial composition of gregarious and solitary females. We investigated its temporal dynamics and how it interacts with the locust phase, by comparative sampling and 16S rRNA amplicon sequencing. We revealed that the bacterial composition of the locust female reproductive tract is mostly constructed of three core genera: Micrococcus, Acinetobacter and Staphylococcus. While solitary females maintained a consistent bacterial composition, in the gregarious phase this consortium demonstrated large temporal shifts, mostly manifested by Brevibacterium blooms. These data are in accord with our previous report on the dynamics of locust hindgut bacterial microbiota, further indicating that locust endosymbionts are affected by their host population density. These newly understood dynamics may have implications beyond their contribution to our knowledge of locust ecology, as aggregation and mass migration are prevalent phenomena across many migrating animals.

Flea infestation, social contact, and stress in a gregarious rodent species: minimizing the potential parasitic costs of group-living.

Both parasitism and social contact are common sources of stress that many gregarious species encounter in nature. Upon encountering such stressors, individuals secrete glucocorticoids and although short-term elevation of glucocorticoids is adaptive, long-term increases are correlated with higher mortality and deleterious reproductive effects. Here, we used an experimental host-parasite system, social rodents Acomys cahirinus and their characteristic fleas Parapulex chephrenis, in a fully-crossed design to test the effects of social contact and parasitism on stress during pregnancy. By analysing faecal glucocorticoid metabolites, we found that social hierarchy did not have a significant effect on glucocorticoid concentration. Rather, solitary females had significantly higher glucocorticoid levels than females housed in pairs. We found a significant interaction between the stressors of parasitism and social contact with solitary, uninfested females having the highest faecal glucocorticoid metabolite levels suggesting that both social contact and infestation mitigate allostatic load in pregnant rodents. Therefore, the increased risk of infestation that accompanies group-living could be outweighed by positive aspects of social contact within A. cahirinus colonies in nature.

Sexual and reproductive traits of the pearl oyster shrimp Pontonia margarita (Decapoda: Palemonidae), symbiotically inhabiting the mantle cavity of the rugose pen shell Pinna rugosa (Bivalvia: Pinnidae)

Symbiosis between decapods and mollusks provides a unique opportunity to examine some of the evolutionary strategies employed by marine invertebrates. We describe the sexual and reproductive traits of the pearl oyster shrimp, Pontoniamargarita Verril, 1869, found symbiotically inhabiting the mantle cavity of the rugose pen shell, Pinnarugosa Sowerby, 1835. Solitary males and females (ovigerous and non-ovigerous) and heterosexual pairs (with ovigerous and non-ovigerous females) were found in a total of 47 rugose pen shells collected from a sandy area with seagrass meadows on the southeastern coast of the Gulf of California, Mexico. The body length (BL) of female P.margarita was correlated with the shell volume of their rugose pen shell host. The sex ratio was female-biased (0.85M:1F). Female P.margarita were larger than their male counterparts in terms of BL, cephalothorax length (CL), and the maximum chelae length of the second pereopod (MCL). The CL and MCL were more strongly correlated for males (r = 0.70, p = 0.01). The number and volume of eggs per ovigerous female varied from 95 to 1,571 and from 5.46 ± 0.48 to 8.85 ± 0.97 mm3, respectively. Our results indicate polygamous behavior and social monogamy among P.margarita, and a short-term pairing system for their association with P.rugosa.

Social organization of boreal woodland caribou (Rangifer tarandus caribou) in response to decreasing annual snow depth

Global climate warming is causing reductions in the depth and duration of snow cover across much of the distributional range of threatened boreal woodland caribou (Rangifer tarandus caribou). Plasticity in group size and composition among gregarious ungulates likely reflects a response to a variety of proximate factors, including environmental conditions such as snow depth. Yet, longitudinal studies of social organization by ungulates in response to environmental conditions are limited. We used 11 years of aerial survey data to examine winter group size in a northern population of boreal woodland caribou in response to late-winter snow depth. We documented caribou social organization (size and types of groups) and annual variability in group size. We tested the hypothesis that group size increases with increasing snow depth. Most groups (61%; n = 456) were ≤ 5 animals; however, they only constituted 37% of the animals. Caribou were distributed among four types of groups, including solitary females, males only, females only, and mixed groups. Group sizes differed among group types. Mixed groups were both the most common and largest groups encountered in late winter. We found a positive relationship between snow depth and group size; however, there was no relationship between snow depth and the percentage of mixed groups. These caribou may form larger groups in winters with deep snow as a behavioral strategy to reduce energetic costs, predation risk, or both. Climate-induced decreases in late-winter snow depth will likely reduce group sizes in boreal woodland caribou. However, further work is required to understand if this change in social organization will affect the persistence of local boreal woodland caribou populations.

Re-examination of the maternal control of progeny size and body color in the desert locust Schistocerca gregaria: Differences from previous conclusions

The desert locust shows conspicuous phase polyphenism of various traits in response to crowding conditions. Gregarious females lay larger eggs that produce black hatchlings, whereas solitarious females lay smaller eggs that produce green hatchlings. Previous studies have shown that changes in egg size and hatchling body color occurred easily in the laboratory upon exposure of the female parent to crowding or isolation for as few as 2 days. Based on these observations, these studies concluded that female adults perceive crowding stimuli with their antennae and require light for perception of the stimuli, with contact chemicals present on the integument of sexually mature males that are responsible for the crowding effect. We undertook this study to identify the chemical structures of the reported contact substances, which remain unknown to date. However, we could not reproduce the main results reported in the aforementioned studies and found that egg size and hatchling body color did not alter easily, even after crowding or isolation of the female parent for 2 days or longer. We were not able to observe a change in the progeny crowding characteristics by stimulating the antennae of female adults through either physical contact with male adults or using hexane extracts of their body surfaces. Similarly, the importance of light for gregarization or solitarization was also ruled out. These results indicate that some of the conclusions of previous studies should be reconsidered.

Sexual Behavior of the Desert Locust During Intra- and Inter-Phase Interactions

Mating and reproduction behaviors and strategies are fundamental aspects of an organism’s evolutionary and ecological success. In locusts, intra- as well as inter-phase reproductive interactions among gregarious and solitarious locust populations have a major impact on the locust population dynamics. However, practically all previous work on locust sexual behavior has been limited to the gregarious phase. Here we provide a first detailed description of pre-copulatory behavior of solitarious desert locusts. We compare our findings with those of previous reports of pre-copulatory behavior of gregarious locusts, focusing on the behavioral elements that serve in inter-sex signaling and communication. We also studied inter-phase (mixed pairs) reproductive interactions. Solitarious males were found to invest more in pre-copulatory courtship and signaling compared to their gregarious counterparts; and solitarious females played a more dominant role in the inter-sex communication than gregarious females. The solitarious females were also less likely to demonstrate rejection-related behavioral patterns than gregarious females. As a consequence of the particular characteristic behavior of each phase, the most successful among intra- and inter-phase pairs were gregarious males with solitary females. Least successful were solitary males paired with gregarious females, indicating a strong asymmetry in inter-phase reproductive interactions.