The effects of male body size on territorial and mating success in the landmark-defending fly Hermetia comstocki (Stratiomyidae)

Abstract.

• 1 Males of Hermetia comstocki Williston compete for territorial control of certain agaves and yuccas. Winners copulate with females that visit these plants solely to acquire a mate.
• 2 Males vary in body weight by more than an order of magnitude and larger flies almost always defeat smaller ones in aerial contests for control of landmark territories.
• 3 The mean body size (as measured by wing-length) was significantly greater for males retaining residency at a site for at least one hour compared to males unable to do so. Likewise, males able to return to a perch site in the study area on more than one day were larger on average than males unable to do so.
• 4 Male preferences for landmark territories remained similar across years. Large males dominated the perch landmarks most likely to be occupied by males and most likely to be visited by females.
• 5 Despite the fighting and territorial advantages enjoyed by large males, the mean size of males found mating with females was not significantly larger than that of the general population.
• 6 The apparent failure of large males to secure a statistically significant mating advantage may be a statistical consequence of the small sample size of males observed mating. On the other hand, any mating advantage of large males may be reduced because (a) receptive females visit many different landmarks, (b) females mate with the first male they encounter at a landmark, regardless of his size, (c) there are usually many vacant landmarks available for smaller males, and (d) even popular territories are often open to small males, thanks to the low site-tenacity of territory owners.

     

Mating Systems and Male Size in Australian Hylaeine Bees (Hymenoptera: Colletidae)

The mating systems of seven previously unstudied members of the colletid bee genus Hylaeus Fabricius and one of Hyleoides Smith are described. Male mating tactics can be categorized as territorial (perched males defend flowers or other sites that attract receptive females) or non-territorial (patrolling males search for receptive females at flowering plants). The four species in which some territorial males occur are characterized by: 1. grappling fights among males for preferred perches; 2. territorial control by larger males; 3. the possession of prominent spines or other projections on the venter of the abdomen in larger males; and 4. the occurrence of some males that are as large as, or larger than, the largest females of their species (the ‘large-male phenomenon’). In contrast, the four species that lack territorial males are distinctive in that males: 1. do not engage in grappling contests; 2. lack abdominal weaponry; and 3. are smaller than the largest females of their species. In addition, we searched for the large-male phenomenon in museum collections of four species of Hylaeus that exhibit male abdominal spines (presumed to be the weapons used by territorial individuals) and two other species that lack these attributes (presumed non-territorial patrolling species). The results tend to support the sexual-selection-for-fighting-ability hypothesis, which argues that the evolution of unusually large males is a selective consequence of aggressive male—male competition for access to mates. The limitations of the present data set as a comparative test of this hypothesis are discussed.     

Non-resource based territoriality in males of the butterflyXamia xami (Lepidoptera: Lycaenidae)

In the Pedregal de San Angel reserve, in Mexico City, males of the butterfly Xamia xamiperch in and defend areas with well-defined topographic limits. These areas lack concentrations of receptive females and of larvae and adult resources. One individual defends the same territory an average of 5 h/day, up to a maximum of 23 days. The same areas are used as territories by different males during the year. These areas share some characteristic features which are described. Evidence is presented in support of the hypothesis that the territories function as mating stations. A possible scenario for the evolution of this territorial mating system is advanced.     

Hilltopping Behavior of Polistes commanchus navajoe (Hymenoptera: Vespidae)

Males of the paper wasp Polistes commanchus aggregate in large numbers on hilltops in central and southeastern Arizona where individual males defend perch sites on shrubs, trees or rocks. Residents chase intruders away quickly and exhibit strong site fidelity at their perches. Takeovers are rare as are prolonged battles for possession of a site. Males have only weak preferences for peaktop perch sites as opposed to those lower on hillsides, and a similarly weak preference for perches in shrubs as opposed to those on rocks. Receptive females appear occasionally at the male aggregation sites to mate with perch holders. The relatively weak territoriality exhibited by P. commanchus may stem in part from the high density of males at peaktops and the correspondingly high rate of interactions. The evolution of hilltopping in a species whose reproductive females are clumped spatially at nest sites poses a puzzle for the ecological analysis of mating systems.     

Hilltopping in the Pipevine Swallowtail Butterfly (Battus philenor)

In central Arizona, receptive females of the pipevine swallowtail, Battus philenor, are widely scattered in time and space, and in this region the butterfly's mating system is one in which males patrol mountain peaks. Hilltopping males engage intruding males in ascending flights that appear to be ritualized aerial combat with individuals defending patrolling sites for relatively short periods on any given day. The day-to-day appearance of marked males is irregular, unlike the site fidelity shown by males of many other hilltopping insects. The distinctive pattern of male territoriality in B. philenor may be partly a response to very low male and female density in the observed population. Males at the hilltop chase, court, and attempt to copulate with virgin females released near them. Males assess the receptivity of females rapidly, and receptive females permit a lengthy copulation to occur after a courtship that lasts less than 30 s. During an initial copulation males pass a spermatophore that weighs about 6% of their body mass, with partners on following days receiving a smaller but still substantial donation.     

Competition for landmark territories among male Polistes canadensis (L.) (Hymenoptera: Vespidae): large-size advantage and alternative mate-acquisition tactics

Alternative male mating tactics of insects at landmarks (leks)have only rarely been investigated. Some males of the paperwasp, Polistes canadensis (L.), were territorial at small treesalong the crests of dry ridges in Santa Rosa National Park,Costa Rica. Territories did not contain nests or resources forwhich females foraged. Contrary to other "hilltopping" species,male P. canadensis competed most intensely for territories insaddles along these ridges rather than at the highest points.Nonterritorial males patrolled small areas of the ridge line,following a path that took them to a number of territories.Many males switched between territoriality and patrolling, suggestingthat both size-related tactics belong to one conditional strategy.Males that were territorial on 2 or more days were larger thanthose that were territorial on only 1 day, and these in turnwere larger than permanent patrollers. Moreover, the mean sizeof territorial males was positively correlated with two measuresof territory attractiveness, suggesting that larger males monopolizepreferred sites. Mean age of territorial males was also relatedto territory attractiveness, but males of intermediate age claimedthe most attractive territories.     

The Behavioral Significance of Male Body Size in the Tarantula Hawk Wasp Hemipepsis ustulata (Hymenoptera: Pompilidae)

Large males of the tarantula hawk wasp Hemipepsis ustulata appear to have an advantage in the competition for mates. Large males are more likely to acquire perch territories used to scan for incoming receptive females and territorial males appear more likely to mate than non‐territorial males. In addition, among the males that do secure a mate, those that intercept a female on a territory are larger than those that do so elsewhere. Despite the mating advantages apparently enjoyed by larger males of this species, average male size has remained essentially constant over the last 25 yr. Moreover, larger males are not seen to employ certain competitive tactics that might otherwise enhance their reproductive success. Thus, larger males did not preferentially visit the most popular landmark territory compared to a site that attracted fewer visitors overall. Nor were larger males more likely to return to potential territories after marking, capture, and release, either immediately or on a subsequent day. Finally, although large males made up a significantly greater proportion of the males captured at two territories as the 2005 flight season progressed, over all the years of the study, receptive females have not been concentrated in the latter part of the flight seasons.     

Strategic responses of male samango monkeys (Cercopithecus mitis) to a decline in the number of receptive females

Observations on a habituated troop of samango monkeys (Cercopithecus mitis)revealed that lone males did not achieve significant mating opportunities during a breeding season in which few females were sexually receptive. This stood in contrast to the previous year and was associated with the maintenance of shorter resident male-female distances, confirming suggestions that the reproductive benefits of residency are associated primarily with low numbers of simultaneously receptive females. At the same time, lone males made no attempt to challenge the resident male physically in order to gain access to females. Given the presence of a stable bachelor group and the absence of other, transient, males, these data are used to argue for male mating strategies that are sensitive to regional and temporal variability in the availability of receptive females.     

Choice of Lookout Posts by Territorial Amberwing Dragonflies, Perithemis tenera (Anisoptera: Libellulidae)

Many territorial insects use specific perches, or lookout posts, from which they perceive and react to conspecific males and females. We investigated the lookout post choice of territorial male amberwing dragonflies (Perithemis tenera). An observational study indicated that males rarely perched directly at their oviposition site; rather, they perched farther out from shore than, and within 2 m from, their oviposition site. In an experimental study, we provided an array of perches at different distances from the shore and oviposition site to eliminate perch limitation as a factor in perch choice. The results of the experimental study confirmed the patterns evident in the observational study; males perched farther from shore than their oviposition site was located. Interestingly, in both the observational and the experimental study, when neighbors were close, a male perched away from his closest neighbor, which usually resulted in his oviposition site being closer to his neighbor than he was. Thus, male amberwings apparently alter their perch choice within their territories in response to the location of other males. These lookout post locations may provide the best opportunity for the territorial male to perceive passing females and intruding males, while minimizing conflict with their neighbors.     

Host plant-based territoriality in the white peacock butterfly,Anartia jatrophae (Lepidoptera: Nymphalidae)

Mate locating behavior of Anartia jatrophaewas studied near Ochopee, Collier County, Florida. Males were individually marked, and focal animal samples were used to determine activity, residency, and interactions with other butterflies. We recaptured more than half of 53 marked males within the study area on subsequent days. Marked males restricted non-feeding activity to roughly circular areas typically less than 15 m in diameter. Males showed considerable site fidelity and chased both conspecifics and a variety of other insects. Typically, encountered individuals flew away, and the resident peacock male returned to perch near his previous perch. Encounters with conspecific males averaged 38 sec, three times longer than with other insects. Such site fidelity combined with aggressive interactions indicates territorial behavior. When male density more than doubled, site fidelity decreased, resident turnover increased, and areas that had not been defended at lower density were defended. Without exception, defended sites contained the larval host, Bacopa monnieri.In butterfly mating systems, defense of host plants appears to be much less common than defense of natural features such as landmarks.     

Influences on variation in territorial tenures of male white-faced dragonflies (Leucorrhinia intacta) (Odonata: Libellulidae)

Some individuals in species with extended periods of territorial occupancy may change territory locations within a single bout of territorial activity. Length of occupancy of mating territories among males in a local population of white-faced dragonflies (Leucorrhinia intacta) varied from more than 6 h to 15 min or less. Males with short tenures often established territories in several locations on the pond during a day. Several hypotheses have been proposed to explain shifting territorial sites rather than remaining in a single site during one bout of territoriality. We attempted to test the hypothesis that males shift to leave low-quality sites. Site quality may be affected by costs of defense in relation to intruder rate and the mating benefits of holding the territory. To test whether variation in these possible effects of benefits and costs of territoriality influenced tenure, we manipulated local quality of oviposition substrate and perch density. The quality of oviposition substrate, but not perch density, influenced both potential benefits and costs of territoriality. Female density was higher in areas with good substrate, but so were rates of males intruding into the territories, rates of chasing by territorial males, and local density of territorial males. More matings occurred in areas with good substrate, but among males with tenures of 15 min or more, mating success per male and tenure lengths did not differ statistically among treatments. Defense costs were low for all treatments and perhaps were not an important influence on tenure duration. Territorial males in this population probably adjusted local density to expected mating success by initial choice of site rather than by varying tenure length. Variation in tenure length at a site resulted, in part, from stochastic external factors, such as predation attempts.     

Mating behavior of male deer ticksIxodes dammini (Acari: Ixodidae)

To analyze the sexual behavior of male black-legged deer ticks Ixodes dammini,we collected ticks infesting 202 white-tailed deer. On average, 17.7 males and 8.8 females infested each deer. Field-collected males copulated with a mean of 2.25 females, and virgin males mated with 2.4 females. On experimental hosts, males established sexual contact with feeding females and repelled other males, and about half remained paired after their mate detached. Engorged females continue to be receptive, and males mate more readily with them than with nonfed females. We conclude that male I. damminiare endowed with a repertoire of behaviors which favor an opportunistic mating before seeking a host and a preference for mating with feeding females on the host accompanied by tenacious mate guarding.     

Studies on the mating system of the winter cherry bug,Acanthocoris sordidus Thunberg (Heteroptera: Coreidae) II. Harem defence polygyny

The mating system of the winter cherry bug, Acanthocoris sordidus, was analyzed precisely. As a result, it was found that male adults of this species establish a small territory for mating on the stem of host plant which harbors females. These males abandoned their territories soon after the disappearance of monopolized females. Thus it was confirned that the cue for the territorial establishment of males is the presence of females per se on the host plant. Moreover, most aggregations of adults observed on the host plant contained only a single male. This one-male unit in the mating was named a harem. Harem holding males were usually big in body-size and had a high chance of copulations. The defence behaviors of harem holding males, the mating disparity among males, and the oviposition habit of females in relation to the mating system, were observed. The results obtained were discussed in relation to the sexual selection theories.     

Mating tactics and male wing dimorphism in the damselfly,Mnais pruinosa costalis selys (Odonata: Calopterygidae)

Males of the damselfly,Mnais pruinosa costalis, exhibit wing color dimorphism: one form has orange wings, and the other hyaline wings which resemble female wings. The former is usually territorial and the latter uses sneaky mate securing tactics. When orange-winged males failed to establish territory, they became floaters that day. Hyaline-winged males perched around their territories and often, formed in tandem without any apparent courtship behavior when they found females. Their copulation frequency was higher and copulation duration longer than those of territorial males. A few females oviposited without remating. Total oviposition duration of females with which a hyaline-winged male mated was more than 32 min per male on average in a day Females that copulated with hyaline-winged males often remated with orange-winged residents before oviposition. Total duration of oviposition bouts of females after mating with floaters was short (15 min), while that with territorial residents was long (66 min). As a result, total oviposition duration of females with which an orange-winged male mated was about 40 min in a day. The reproductive success of the hyaline-winged males may be similar to that of the orange-winged males.     

Male mate-locating behavior inEuphydryas chalcedona (Lepidoptera: Nymphalidae) related to pupation site preferences

Males of the checkerspot butterfly (Euphydryas chalcedona)patrol and perch near but not on the larval foodplant in search of females. Experiments with tethered butterflies show that searching males chase virgin females for longer times than they do mated females or males. The larvae leave the larval food-plant to pupate. The correspondence between the distance from the larval foodplant to pupation sites and where males search for females suggests that male mate-locating behavior has evolved to maximize the rate of encounters with newly emerged, virgin females. These conclusions are compared to a recent analysis of butterfly mating systems by Odendaal et al. (Am. Nat. 125: 673–678, 1985).     

Spatial organization of the fat dormouse (Glis glis) in an oak-hornbeam forest during the mating and post-mating season

Home range (HR) size and overlap, movements, and nest site use of fat dormice Glis glis (Linnaeus, 1766) were studied by live-trapping and radiotracking in the Bialowieza Forest in north-eastern Poland. The study was conducted during a mast year of oak Quercus robur (2001) and hornbeam Carpinus betulus (2002). Average HR size measured by 100% minimum convex polygons varied from 3.6 to 7.0 ha in males and from 0.55 to 0.76 ha in females. HR size in males was significantly larger in the hornbeam mast year than in the oak mast year, which was probably due to the lower energy value of hornbeam mast. Males had significantly larger HRs and used more nest sites than females. In contrast to females, HRs of males overlapped extensively. In the mating season, core areas of males overlapped significantly more and they shared their core areas with more males than in the post-mating season. During the mating season, males were found to share nest sites with other males or with a single female. Additionally, groups of 2–3 males were observed aggregating around a female during the mating season. Our data suggest that fat dormice have a promiscuous mating system where the females are territorial, and the non-territorial males directly compete for access to receptive females during the mating season.     

Post-copulatory mate guarding by males of the demselfly Hetaerina vulnerata Selys (Odonata: Calopterygidae)

Males of the calopterygid damselfly Hetaerina vulnerata remain with their mates after copulating with them. The species exhibits two unusual features of post-copulatory mate guarding. First, a male will often leave his territory to accompany a female in tandem on a search for oviposition sites elsewhere. Second, a male will perch near his ovipositing female even though she completely submerges when egg-laying and cannot be captured and mated by another male while she is underwater. These activities carry two potential costs: (1) a male may miss other receptive females while guarding one mate and (2) he may lose his territory to an interloper while he is absent. These costs were low, however, because territorial males secured only one mating per 3.6 days on average. Moreover, 23 times out of 26, territorial males reclaimed their plots quickly after being away for 30–60 min. The gain from postcopulatory guarding came from being present to recapture a female should she fly up from the water after rejecting an oviposition site. There was a 40% chance that a female would leave one site to search for another during an oviposition bout. If the male were not present, his mate would be captured and mated by another individual (no female ever selected an oviposition site without being carried to it by a male). Her new partner would fertilize the remaining eggs in the female's clutch (if sperm precedence occurs in this species). The total number of eggs fertilized by a male will be affected by how well he prevents any one mate from copulating again before she lays her entire clutch and the total number of receptive females he captures. The variation in the degree of mate guarding by male odonates seems to be the evolutionary outcome of differences in fitness gains derived from these two competing activities in different ecological settings.     

Timing of mate-locating by males in relation to female activity in the carpenter beeXylocopa varipuncta (Hymenoptera: Apidae)

Males of the carpenter beeXylocopa varipuncta Patton wait for females to visit them as they hover at landmark territories along ridgelines on some spring afternoons. While hovering, males advertize their presence by releasing a pheromone that attracts passing females. If males have limited time to invest in territorial hovering and signaling, then they should engage in these activities more often at times when mate-searching females are most likely to visit landmark territories. The number of females flying near male territories varies greatly over the course of afternoons and from day to day. Measures of female activity and male territorial activity were highly correlated at one study site, both in terms of changes within afternoons and in terms of day-to-day fluctuations. This result supports the hypothesis that males ofX. varipuncta time their mateattracting behavior to maximize contacts with receptive females.     

Territoriality and Male Mating Success in the Dart-poison Frog,Epipedobates femoralis (Dendrobatidae,Anura)

The social and reproductive behaviour of the dart-poison frog, Epipedobates femoralis, was studied in Amazonian Peru for 14 months. Males defended territories with advertisement calls and, ultimately, fighting. Territory size ranged from 0.25 to 26 m² and was positively correlated with duration of residence and calling activity of the owner. Females were not territorial and were never attacked when approaching calling males. Males and females only mated once and females sampled calling males before mating. Male mating success was closely correlated with territory size and calling activity. No correlation was found between male body size and mating success. Territories provide residents with sufficient space for mate attraction and reproduction without interference from rivals. Since territory size is dependent on calling activity which involves high energetic costs, it is suggested that territory size reveals male quality.     

Attraction of the sexes inFormica lugubris Zett (Hymenoptera: Formicidae)

Summary Sexuals ofFormica lugubris fly to mating places, where females attract males by using a sex pheromone. Females collected on the nest surface before departing on a mating flight are much less attractive than those collected on the mating place after the mating flight, suggesting that the mating flight triggers the release of the sex pheromone. Olfactory cues are essential for males to locate females while they patrol. Males probably use visual cues to locate females once they have alighted nearby them. Males are also attracted by aggregations of other males on the ground, probably because one or several females are likely to be close to male aggregations.