Reproductive strategy in orphaned colonies of Myrmica kotokui Forel, the Japanese species of the M. ruginodis complex (Hymenoptera, Formicidae)

Summary: The reproductive strategy between queen-right and orphaned colonies of Myrmica kotokui was compared. The ratio of orphaned colonies reached about 30 percent in the field. Although colony size was significantly smaller in orphaned colonies, the mean body size and mean ovariole length of the workers were significantly larger than those in queen-right colonies. The reproductive individuals in orphaned colonies were also significantly larger than those in queen-right colonies. Only 38.5 % of the orphaned colonies, however, contained eggs during the reproductive season, compared to 100 % of the queen-right colonies. This indicates that worker reproduction under natural conditions is relatively low, even in orphaned colonies.     

Testing male immunocompetence in two hymenopterans with different levels of social organization: ‘live hard,die young?’

Males are under different selective pressures than females, which results in differences in the physiology of the two sexes to maximize their fitness. In terms of immunity, males are typically considered as the ‘sicker sex’, where immunocompetence is reduced to favour increased reproductive output. However, male social Hymenoptera are also haploid and therefore lack allelic variation at the individual level, which can also lead to reduced immunocompetence. Over the last decade, several studies have provided evidence for a higher susceptibility to disease in males of social Hymenoptera, without clarifying whether this susceptibility was a direct consequence of their haploid condition or the result of a ‘live hard, die young’ overall evolutionary strategy. In the present study, we used an experimental approach of bacterial challenge to test the immune response of males and females in two species of social Hymenoptera (honey bees, Apis mellifera; paper wasps, Polistes dominula), where males show very different life‐history traits. Drones benefit from colony protection for most of their life, whereas P. dominula males leave their colonies and have to survive for weeks at leks. If the haploid condition is responsible for a higher susceptibility in males, we should expect a lower immune response in males of both species compared to females. Conversely, if the immunocompetence depends on the life‐history traits of males, an opposite trend is expected in males of the two species. Our results do not support the ‘haploid susceptibility hypothesis’ but are in accordance with the different life history of males from the two species. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114 , 274–278.     

Impact of orphaning on field colonies of Southeast Asian Macrotermes gilvus (Hagen) and M. carbonarius (Hagen) (Termitidae, Macrotermitinae)

Field colonies of Macrotermes gilvus (Hagen) and M. carbonarius (Hagen) were experimentally orphaned to examine their potential for producing replacement reproductives. Orphaned colonies were investigated only once for caste composition at selected time intervals at 3, 6, 9 or 12 months after orphaning. Of the 38 orphaned colonies of M. gilvus, 15 colonies (39.5%) re-established. In M. carbonarius, three colonies out of 20 (15%) re-established. Re-established colonies were headed by adultoids which were morphologically indistinguishable from primary reproductives. In naturally orphaned colonies of M. gilvus, we often found multiple adultoids with normal pigmentation but torn wings, i.e. the colonies retained alates as replacement reproductives. The number of reproductives probably declines over time. It may take alates of M. gilvus 6 months to develop into functional adultoids, and up to 12 months for alates of M. carbonarius. Our results also demonstrate that the presence of sexual castes (nymphs or alates) at the time of orphaning does not necessarily guarantee the success of colonies in re-establishing themselves as breeding colonies. We also found a high prevalence of occupation of the mounds by other termite species, after the death of M. gilvus (18.4%) or M. carbonarius (30.0%) colonies, probably using them as foraging sites.     

Long-term impact of orphaning on field colonies ofCoptotermes lacteus (Froggatt) (Isoptera: Rhinotermitidae)

Summary Colonies ofCoptotermes lacteus (Froggatt) from a site in coastal south-eastern Australia were experimentally orphaned in early 1989. Sample colonies were examined 3, 6, 12, 18, 24 or 30 months later for their caste composition, the presence of replacement reproductives and brood. All replacement reproductives were nymphoid neotenics. The number of functional (physogastric) females ranged from 1 to 27; this variability was maintained irrespective of the length of time between orphaning and inspection of the colonies. The average live mass of individual females stayed at 30 to 40 mg over the period of 6 to 30 months after orphaning in groups of more than five neotenic queens, but increased from 38 mg three months after orphaning to about 125 mg after 24 months in colonies headed by fewer than five neotenic females. The combined live mass of neotenic females could approach or even exceed that of primary queens. Two key features characterized experimentally and naturally orphaned, neotenic-headed colonies: (1) Nymphs differentiated in significant numbers all year round for a period of at least 30 months right from the time neotenics commenced breeding (in primary-headed colonies nymph production is strictly seasonal). (2) All or most nymphs were males (in primary-headed colonies the sex ratio of nymphs is more or less balanced). The mechanism(s) for achieving the male-biased sex ratio is (are) unknown. Even when colonies have resumed breeding with the help of neotenics, colony survival is not guaranteed. Under such circumstances the gene pool is best preserved if colonies were to raise and release large numbers of alates as potential founders of new colonies. By producing largely male nymphs orphaned colonies ensure outbreeding and may prevent competition (and its disruptive impact an breeding) between existing reproducing neotenic queens and newly differentiating female neotenics. Competition between male neotenics is unlikely to have any impact on the rate of brood production and therefore would not require a mechanism to prevent it from occurring.     

Male production by workers in the polygynous ant Prolasius advenus

The ability of workers to produce male individuals is reported here for the first time in a species of the formicine ant genus Prolasius. We show that Prolasius advenus workers possess ovaries and demonstrate that they are able to produce adult males in queenless colonies. We also experimentally tested the influence of queen volatiles on the level of worker reproduction. Workers produced fewer eggs in treatments where they could perceive odors from queens. Some volatile compounds emitted by queens may thus have a signaling or inhibitory effect on worker reproduction. This effect of queen presence did not entirely stop worker reproduction, however, as adult males still emerged under these conditions. Worker-produced males were absent only in treatments with the physical presence of queens. Dissections of workers collected from queenright nests in the field revealed signs of egg-laying activity in more than half of individuals. Together, these results suggest that in nature P. advenus workers produce males at least in orphaned colonies or in situations where the physical presence of queens is limited.     

Male Behavior and Regulation of Worker Mating in a Ponerine Ant, Pachycondyla (Bothroponera) sp. (Hymenoptera: Formicidae)

Male behavior and regulation of worker mating were observed in Indonesian Pachycondyla sp. The colonies had some mated workers but only one gamergate (mated and egg-laying workers). Males frequently tried to mate with workers in their natal nests irrespective of worker age and dominance rank, however, workers never accepted mounting of nestmate males. Worker mating occurred only under the gamergateless condition with alien males.     

Inconspicuous matured males of worker form are produced in orphaned colonies of Reticulitermes speratus (Isoptera: Rhinotermitidae) and participate in reproduction

Differentiation of neotenics is easily induced by orphaning the worker termites of Reticulitermes speratus (Kolbe). Although it has previously been reported that the sex ratio of neotenics is female-biased, the background of this phenomenon and the gonad developmental process of workers in artificially orphaned colonies are unknown. Although both male and female conspicuous neotenics can emerge as a response to the orphaning of the colony, we observed that majority of the reproductive males that are formed do not molt into the neotenic morph and are therefore inconspicuous in the population. Participation of the inconspicuous reproductive males in sexual reproduction was confirmed by genetic analysis. Slight pigmentation of the abdominal sternites is the only characteristic of the inconspicuous reproductive males that enables them to be distinguished from normal male workers. The presence of the female ergatoid (one type of female neotenic) did not induce the production of inconspicuous reproductive males during the 12-week experiment time.     

Sexual selection in the socorro isopod, Thermosphaeroma thermophilum (cole) (Crustacea: Peracarida)

Females and parental males commonly discriminate among potential mates. Male discrimination is often assumed to be lacking in species with non-parental males. However, male competition in these species may favour male discrimination since indiscriminate matings may waste time and energy. Males in such species should attempt to maximize their fertilization rates; females in such species should mate only with males able to enhance female reproductive success. Males of the Socorro isopod, Thermosphaeroma thermophilum, engage in precopulatory guarding, preferring larger, more fecund females and females near a reproductive moult. Males also guard post-moult females. Large males prevail when usurping or resisting usurpation, and guard large females. Females may choose mates by selective resistance to insemination attempts.     

Production of Sexuals and Mating Frequency in the Stingless Bee Tetragonisca angustula (Latreille) (Hymenoptera, Apidae)

Queen, worker, and male production was studied for 1 year in three queenright colonies of Tetragonisca angustula (Latreille). We sampled brood combs monthly and noticed that the number of brood cells and production of individuals were similar among colonies. Although the production of queens did not vary significantly, the frequencies of workers, males, and the number of cells among the combs varied over time. The production of males was highly seasonal, occurring mostly from February to April, coinciding with the period of intense brood cells production, when colonies produced more males and less workers, resulting in a negative correlation. Although the frequency of queens has not varied in time, the seasonal availability of males affected the mating frequency and the time spent since emergence until fertilization of queens. In the T. angustula colonies studied, the population dynamics was highly seasonal and the mating success depended of male production, according to the season.     

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).     

Larval development of Diploptera punctata reared alone and in groups

Larvae of the cockroach Diploptera punctata were reared in isolation, in pairs, or in groups of 8–10. Duration of larval development, age at each ecdysis, weights at birth and ecdyses, and adult head-capsule width were measured. Duration of larval development was longer and adult size was larger in isolated animals than in animals reared in pairs and groups. The effect of isolation on development was more pronounced in males. All females had 4 larval instars, whereas males had 3 or 4 instars. The proportion of males with 4 larval instars was higher among animals reared in isolation. There was no difference in the duration of larval development or adult size between pair- and group-reared animals. The sex of animals in the group did not affect adult size or the duration of larval development. Males which underwent 3 or 4 larval instars had different schedules of moulting. Rates of growth of males of both instar types reared in isolation and pairs were similar. Greater adult weight of isolated animals and 4-instar-type males was a result of their longer duration of larval development. Both a higher rate of growth and longer duration of larval development contribute to the larger adult size of females than males.     

Colony productivity of <Emphasis Type="Italic">Polistes dominula</Emphasis> (Christ) (Hymenoptera,Vespidae: Polistinae) wasps nesting on plants by haplometrosis: Regression analysis

The paper presents the results of analysis of the relationships of various colony characteristics in the resocial wasp Polistes dominula nesting on plants in the south of Ukraine (Kherson Province, the Black Sea Biosphere Reserve) in 2003–2007. The number of future foundresses and nest size at the end of the life cycle depend on the queen longevity and on the number of workers in the colony. The number of males reared in the colony is positively correlated with the nest size (the number of cells) and negatively correlated with the queen longevity. An increase in the share of the brood infested by the parasitoids Latibulus argiolus (Hymenoptera, Ichneumonidae) and Elasmus schmitti (Hymenoptera, Eulophidae) results in a smaller nest size and a smaller number of males reared.     

Social Network Analysis of Male Dominance in the Paper Wasp Mischocyttarus mastigophorus (Hymenoptera: Vespidae)

Social aggression is a pervasive feature of insect societies. In eusocial Hymenoptera, aggression among females can affect task performance and competition over direct reproduction (egg laying); in most species males participate in social interactions relatively rarely. Males of the independent-founding paper wasp Mischocyttarus mastigophorus are exceptional: they are aggressive toward female nestmates, leading us to explore the function of this unusual behavior. We applied social network analyses to data on M. mastigophorus social aggression to quantify sex differences in giving and receiving social aggression. The network analyses supported the pattern of biased male aggression toward female nestmates; females are relatively rarely aggressive to males. We then asked whether male aggression toward females was biased by females’ relative ovary development. Males were more aggressive toward females with better-developed ovaries, opposite to patterns of aggression among females. Because food brought to the colonies is often monopolized by dominant females, we suggest that males direct aggression toward socially dominant females with better-developed ovaries to obtain food. The implications of biased male aggression for female task performance and physiology are unknown.

     

The Association of Two Gall Crabs (Brachyura: Cryptochiridae) with the Reef-building Coral Siderastrea stellata Verrill, 1868

The family Cryptochiridae includes a small group of cryptic crabs that inhabit cavities in scleractinian corals. They are represented in Brazil by two species. Troglocarcinus corallicola, found from Maranhão to Bahia states and that occurs in many species of the coral families Mussidae, Faviidae, Caryophillidae and Siderastreidae. Opecarcinus hypostegus, reported from the state of Pernambuco, is mainly associated with Agaricia fragilis. The range of O. hypostegus is extended to Rio Grande do Norte and Alagoas states. Males are usually smaller than females, and couples may be eventually found sharing cavities. Ovigerous females and males of O. hypostegus are recorded for the first time inhabiting adjoining cavities on colonies of Siderastrea stellata, an endemic reef coral widespread along the Brazilian littoral.     

Individual recognition is associated with holistic face processing in Polistes paper wasps in a species-specific way

Most recognition is based on identifying features, but specialization for face recognition in primates relies on a different mechanism, termed ‘holistic processing’ where facial features are bound together into a gestalt which is more than the sum of its parts. Here, we test whether individual face recognition in paper wasps also involved holistic processing using a modification of the classic part-whole test in two related paper wasp species: Polistes fuscatus, which use facial patterns to individually identify conspecifics, and Polistes dominula, which lacks individual recognition. We show that P. fuscatus use holistic processing to discriminate between P. fuscatus face images but not P. dominula face images. By contrast, P. dominula do not rely on holistic processing to discriminate between conspecific or heterospecific face images. Therefore, P. fuscatus wasps have evolved holistic face processing, but this ability is highly specific and shaped by species-specific and stimulus-specific selective pressures. Convergence towards holistic face processing in distant taxa (primates, wasps) as well as divergence among closely related taxa with different recognition behaviour (P. dominula, P. fuscatus) suggests that holistic processing may be a universal adaptive strategy to facilitate expertise in face recognition.     

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.     

Pulp partitioning and worker specialization in polistine wasps (Hymenoptera,Vespidae, Polistinae)

The character of pulp partitioning was studied in three Palaearctic polistine wasps (Polistes dominula and P. gallicus in the Black Sea Biosphere Reserve, and Polistes nimpha in the Lugansk Nature Reserve, Ukraine) and in five Neotropical species (P. lanio, P. versicolor, Mischocyttarus injucundus, M. alfkeni, Metapolybia cingulata, and Protopolybia exigua in Trinidad). In independent-founding Polistes and Mischocyttarus species, all cases of pulp partitioning were connected with aggression on the part of the foundresses. An experimental increase of nesting density of P. dominula led to changes in the relative abundance of workers in the polyethic task groups. Some workers practically stopped hunting and switched over to pulp delivery; some of these workers possessed well-developed ovaries and were able to lay eggs. The experimentally removed part of the nest envelope in the swarm-founding wasp Metapolybia cingulata was restored only in colonies that included young workers. The specific features of nest building activity in independent-founding and swarm-founding polistine wasps are discussed.     

Worker dominance and policing in the ant Temnothorax unifasciatus

In many species of eusocial Hymenoptera, conflict about the production of males is resolved through “policing.” Recent studies in wasps and the ant Temnothorax unifasciatus suggest that in these species policing workers are dominant themselves and selfishly increase their own chances of later becoming fertile. Policing may therefore to some extent be associated with dominance and selfishness, and dominance and policing behaviour are indeed difficult to distinguish and often not mutually exclusive. Moreover, selfish policing requires that workers form rank orders already in the presence of the queen. Here, we try to allocate aggressiveness by workers towards policing and/or dominance behaviour and investigate whether hierarchies based on subtle, non-aggressive interactions exist in queenright colonies of the ant T. unifasciatus. We either split colonies into a queenright and queenless halve or temporarily removed the queen from complete colonies, which in both cases allows a few dominant workers to lay eggs in the queenless colony. Reunification of colony halves and return of the queen to orphaned colonies led to aggression against those workers that had become fertile during the absence of the queen. Dominant workers in reunited, split colonies were more severely attacked than those in orphaned colonies after return of the queen. Furthermore, we observed that workers, which later became dominant egg layers under queenless conditions, have more contact with the queen than other workers. Both results corroborate the existence of rank relationships among workers in queenright colonies and show that results from policing experiments may be affected by the disturbance of pre-existing hierarchies through colony splitting.     

Mate guarding and alternative reproductive tactics in the ant Hypoponera opacior

In many animals, males have evolved weapons, elaborate courtship displays, or costly ornaments to increase their reproductive success. Ants, in contrast, commonly mate during nuptial flights, in which males do not profit from fighting or attempting to monopolize females. However, where mating occurs in the nest, males can use other reproductive tactics. We found that wingless (apterous) males of Hypoponera opacior sat on top of queen cocoons, inserted their genitalia into the cocoons and remained in copula with cocooned queens for up to 40 h. These males were tolerant of each other; fighting was never recorded. Our observations therefore suggest that wingless males of H. opacior ensure reproduction by copulatory mate guarding. This strategy, although time consuming, presumably reduces the likelihood of subsequent inseminations by other males. Apterous H. opacior males have only a limited amount of sperm available: histological preparations showed that, in contrast to Cardiocondyla fighter males, the testes degenerate in early adult life. Males ofH. opacior have relatively few mating opportunities. Although some wingless males were reproductively active for more than 3 weeks, we observed a maximum of only six matings per male, with a mean slightly above one. SomeH. opacior males used an alternative reproductive tactic of dispersal and outbreeding. We found colonies headed by single, dealate queens, which did not rear wingless sexuals but presumably reproduced through winged reproductives that mate in nuptial flights. The social structure of those colonies contrasted with nests containing wingless reproductives, which were highly polygynous and polydomous.