The influence of ants on the mating strategy of a myrmecophilic jumping spider (Araneae,Salticidae)

Phintella piatensis is an unusual jumping spider because, despite being neither myrmecophagic nor myrmecomorphic, it associates with ants, including dangerous weaver ants. Although salticids typically spin cocoon‐like nests for use as shelters, the nests of Phintella are unusually dense. These play an important role in how Phintella adapts to living with ants. In experiments, intraspecific interaction and mating increased the risk of being killed by ants when there was no accessible nest, while access to a nest eliminated this risk. Additionally, while outside nests, seeing ants made Phintella reluctant to mate, this being an unusual example of a small animal with exceptional eyesight compensating for predation risk when making vision‐based mating decisions. On the whole, the behaviour of Phintella during intraspecific interaction had broad similarity to the pattern that is common in salticids, but with some of the details of courtship suggesting further adaptation to interacting in the presence of dangerous ants.     

Prey-holding abilities of the nests and webs of jumping spiders (Araneae,Salticidae)

Three characteristics of the silk devices of 12 species of Salticidae and three species of spiders from conventional web-building families (Dipluridae, Eresidae and Stiphidiidae) were investigated: macrostructure; prey-holding ability (measured by escape time for five types of insects); and the structure of the silk itself, as revealed by SEM. Five types of salticid nests were recognized, and a few salticids build webs. The webs of the eresid Stegodyphus mimosarum consist of thick structural threads and fine cribellate fibres. Disparity of thread diameter, although not as extreme, was observed in the webs and nests of the other species. In the webs and nests of all species, there were threads that merely rode one over the other without forming junctions and secure ‘naked’ junctions lacking accessory fibres and ‘sleeves’. Ensheathed junctions, which had ‘sleeves’, were found only in webs of Portia (Salticidae) and Cambridgea antipodiana (Amaurobiidae). The cribellate webs of Stegodyphus mimosarum (Eresidae) had greater prey-holding ability than any other webs or nests tested, but all webs and nests were capable of detaining insects at least briefly. The distinctions between spider webs and nests and between sticky and non-sticky webs are discussed.     

Complex display behaviour during the intraspecific interactions of myrmecomorphic jumping spiders (Araneae,Salticidae)

Jumping spiders (Salticidae) are known for their elaborate vision‐based display behaviour, and a sizeable minority of the species in this large family resemble ants. The display repertoire of two ant‐like salticid species from the Philippines is investigated. Myrmarachne assimilis is a specialist ant mimic, closely matching the appearance of the weaver ant Oecophylla smaragdina. Myrmarachne bakeri is a generalist mimic, which, although ant‐like, is not a close match to any sympatric ant species. Myrmarachne are sexually dimorphic, with males having enlarged chelicerae. The copulatory posture of Myrmarachne is unique among salticids, apparently as an adjustment for the male's elongated chelicerae. Details concerning the intraspecific behaviour of Myrmarachne appear to be adjustments to living in environments populated by numerous other animals with similar appearance (ants). However, the specialist and the generalist that were investigated have display repertoires that are broadly similar to each other and to those of more typical salticids. Generally, the display behaviour of Myrmarachne appears not to have necessitated dramatic deviation from typical salticid display and mating strategies.     

Population dynamics and phenology of two congeneric and sympatric lynx spiders Peucetia rubrolineata Keyserling, 1877 and Peucetia flava Keyserling, 1877 (Oxyopidae)

Numerous phenological studies on spiders belonging to the families Oxyopidae, Thomisidae, Lycosidae, Selenopidae (e.g. Selenops cocheleti) and Salticidae (e.g. Psecas chapoda and Psecas viridipurpureus) have been conducted in the neotropical region. However, studies that simultaneously compare population dynamics and age structure in populations of sympatric species are limited, especially in Oxyopidae. The population dynamics and phenology of two congeneric lynx spider (Peucetia rubrolineata and Peucetia flava) were examined in southeastern Brazil. Several characteristics of the age structure were compared between the two spider species. The variation in the total abundance of individuals and age structure and their relationship with climatic variables were similar between the two spiders. Adults of these spiders were present mainly in spring, indicating an annual reproductive cycle and a ‘stenochronous spring’ phenological pattern. The recruitment of spiders occurred in summer for P. rubrolineata and P. flava, followed by successive phenological peaks at all stages of development. Rainfall and temperature had a positive correlation to population flux in the two spider species studied. Despite the significant climatic effects observed in the Serra do Japi, the phenological pattern of the population in this study was not always repeated in other species of spiders (e.g. Selenops cocheleti).     

Population dynamics,seasonality and sex ratio of twig-girdling beetles (Coleoptera: Cerambycidae: Lamiinae: Onciderini) of an Atlantic rain forest in south-eastern Brazil

In this study, the population dynamics and sex ratios of 12 species of beetles of the tribe Onciderini (Cerambycidae: Lamiinae) were investigated from 2002 to 2006 in an Atlantic rain forest of south-eastern Brazil located at the Biological Reserve of the Serra do Japi. The period of activity of adult beetles ranged from October to May, with slight differences among the species. From June to September, adults were not found and we considered them absent. Our findings showed that adults of these beetles were strongly seasonal, and abundances were correlated with climatic factors that occurred up to two months in advance. Sex ratios were skewed to females in most of the species. The factors determining the population dynamic and sex ratios of these insects are discussed.     

Natural history of Peucetia flava (Araneae,Oxyopidae): seasonal density fluctuation,phenology and sex ratio on the glandular plant Rhyncanthera dichotoma (Melastomataceae)

The seasonal density fluctuation, phenology and sex ratio of Peucetia flava (Oxyopidae) on Rhyncanthera dichotoma (Melastomataceae) were investigated during a year in a swamp in southeastern Brazil. Peucetia flava displayed an unusual non‐seasonal life cycle and the population size varied little over the year. The density of Peucetia spiders increased with the increase in abundance of leaves and number of arthropods adhered to glandular trichomes on R. dichotoma leaves. Our findings suggest that seasonal density fluctuation of Peucetia may be influenced by foraging site availability (i.e. leaves) and prey supply (i.e. arthropods adhering to glandular trichomes). The unusual seasonal stability of P. flava may be related to the type of habitat in which this spider occurs (swamp), because of the constant input of allochthonous resources from the water source, i.e. aquatic insects that migrate to the terrestrial environment.     

Population dynamics and reproduction of the hermit crab Calcinus gaimardii (Anomura: Diogenidae) at Inhaca Island,southern Mozambique

The population dynamics and reproduction of Calcinus gaimardii were studied at Inhaca Island, southern Mozambique. Crabs were sampled monthly from January to December 2003 in order to assess abundance, size distribution, sex ratio, reproduction and juvenile recruitment. Calcinus gaimardii is sexually dimorphic in relation to size, with males reaching larger size than females. Sex ratios were female‐biased during most months of the study period. Females were more abundant in the intermediate size classes while males outnumbered females in the largest ones. Reproduction took place year‐round with peaks of breeding activity between August and October. Likewise, juvenile recruitment was continuous for both sexes with high intensity in winter (May and June). Egg number increased with female size.     

Lasalleistichus a new genus of Tetrastichinae (Hymenoptera: Eulophidae) from the Neotropical region,including four new species

ABSTRACT

A new genus, Lasalleistichus, is described based on material from the Neotropical region (Brazil, Costa Rica, Peru). This new genus includes four species: L. albiclava, L. albifasciatus, L. fuscicoxa, L. longicaulis, all spp. n. and described here. The group is mainly female based, males are known only for L. albiclava. There is no biological information available for this group.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:82E08F36-E2C4-42FF-AD12-11B49C272AC6     

Population structure and breeding season of the hermit crab Diogenes brevirostris Stimpson, 1858 (Decapoda,Anomura, Diogenidae) from southern Mozambique

In this study the population dynamics of the diogenid hermit crab Diogenes brevirostris is evaluated focusing on size structure, sex ratio and breeding season. Crabs were randomly taken on a monthly basis from January to December 2003 at Costa do Sol, Maputo Bay, southern Mozambique. A total of 622 crabs was obtained of which 290 were males (46.6%), 170 were non‐ovigerous females (27.3%) and 162 were ovigerous females (26.1%). The overall size frequency distribution was unimodal for males, non‐ovigerous females and ovigerous females. The overall sex ratio (1:1.15) differed from the expected 1:1 ratio. Sexual dimorphism was evidenced by the larger size attained by males in relation to both ovigerous and non‐ovigerous females. Breeding took place year‐round with three peaks of spawning (March, August and December). Despite the high reproductive activity, young recruits were scarce in the population. The present results suggest that the study area is suitable for reproduction and growth whereas recruitment may take place in different areas from that occupied by the adults.     

Population structure and breeding biology of the hairy crab Pilumnus vespertilio (Fabricius, 1793) (Crustacea: Brachyura: Pilumnidae) in southern Mozambique

The population structure and reproduction of Pilumnus vespertilio were studied for the first time in Mozambique. Random samples of crabs were taken monthly from January to December 2002 from a pebble area of Inhaca Island, southern Mozambique. A clear sexual dimorphism was observed in the present population with males reaching greater sizes than females. Sex ratio was female‐biased, and the monthly size–frequency distributions were often bimodal. The annual reproductive cycle of Pilumnus vespertilio was continuous with peaks of breeding in summer. Results suggest that embryonic development may be synchronized within the population as a result of the very high reproductive activity observed in summer. Juveniles are recruited mostly in winter in the study area.     

Specialization in the choice and use of spider silk in the nest of the chaffinch (Fringilla coelebs) (Aves,Fringillidae)

The chaffinch, Fringilla coelebs, is one of a large number of birds from many families that use silk in the construction of their nests. Thirty-eight chaffinch nests collected from around the UK were examined to determine the nature and role of silk in nest construction. A regular survey of web, retreat and cocoon silk availability was made at a study site close to Glasgow, Scotland, over a 12 month period. The only spider web silk found in the nests was of the type produced by cribellate spiders. The majority of silk in nests, however, was spider cocoons, but there was no correlation between the amount of cocoon and web silk used. Nests with more lichen decoration contained more silk, and cocoon silk was particularly associated with the attachment of lichen. Nest construction at the study site took place from late April to mid-May. When nest building began, the availability of suitable web silk had doubled from its winter (lowest) level; however, its abundance continued to rise sharply until the end of May. The possible influence of silk availability on the timing of chaffinch nesting is discussed.     

Analysis of VCR images of pre-oviposition and oviposition behaviour of Culex quinquefasciatus (Diptera: Culicidae) females,in the laboratory

The aim of this work was to study the pre-ovipostion and oviposition behaviour of gravid Culex quinquefasciatus females, under laboratory conditions. Preliminary tests showed that oviposition is initiated from the third day after bloodfeeding and occurs in the first two hours and the eighth to the tenth hour of scotophase. Image analysis showed that females presented different types of exploratory flights, and that the most common was touching the hay infusion with their hind legs, while flying. The two main oviposition behaviours observed were: (1) females that land at the container's inner wall, rub one leg against the other and walk towards the interface between the wall and hay infusion surface to lay the egg raft; (2) females that land on the hay infusion surface, keep four or six legs on the surface, and lay the egg raft. Interestingly, females that touched the hay infusion with their proboscis rejected it as an oviposition substrate.     

Population structure and reproductive biology of the fiddler crab Uca urvillei (Brachyura: Ocypodidae) in Maputo Bay (south Mozambique)

Although fiddler crabs are among the main faunal components in mangrove habitats, few studies have described the population structure and reproduction of tropical species. Such information is important for understanding their life cycle and ecology. In this study, the population structure and reproduction of Uca urvillei were studied at Costa do Sol, a tropical mangrove forest in Maputo Bay, southern Mozambique. Ten 1.0‐m² squares were sampled during low tide periods, between January and December 2003. The population is characterized by normal size distributions, which are slightly skewed to the left. Males on average are larger than females. Males were more abundant than females and the monthly sex ratios were male‐biased. Juveniles were found year‐round but were less common in June and December. Both gonadosomatic index and frequency of ovigerous females showed that Uca urvillei breeds continuously with peaks in summer and a strong decrease in winter. Egg number was proportional to female size.     

Arabella aracaensis,a new species with growth rings on its mandibles,and some remarks on the endoparasitic Labrorostratus prolificus (Polychaeta: Oenonidae) from southeast Brazil

Two new species, Abaxisotima macrocaudata sp. nov. and Abaxisotima forcipiforma sp. nov., are described and illustrated, supplemental illustrations of several known species are provided. A key to species of the genus Abaxisotima Gorochov is presented. The type specimens are deposited in the Museum of Hebei University.     

Nesting dynamic and sex allocation of the oil-collecting bee Centris (Heterocentris) analis (Fabricius, 1804) (Apidae: Centridini)

The study of nesting biology is an important biological aspect for both conservation and management, but despite this, only a few of the over 20,000 described bee species have had their nesting biology studied. The aim of this study was to describe and analyse the nesting biology and dynamic of an aggregation of the cavity-nesting bee species Centris analis during one generation. Twenty-eight females were marked and had their nesting activities documented, 64 nests were sampled, and 113 individuals emerged from these nests. An asymmetry in the sex allocation was observed for this species, and the sex ratio was male-biased in the first nests built. Nonetheless, considering an individual-level perspective, the females showed different strategies, with some of them producing more daughters, other females producing more sons, and still others producing an equal proportion. The productivity per female was low compared to that of other solitary bee species, and the females displayed an aggressive usurpation behaviour against conspecific females and performed an intraspecific parasitism. As the substrate used to nest is a limiting factor for this species, the usurpation behaviour may be an important strategy that could increase the chance of nesting. A few males used the nesting site as a resting place and the fidelity observed to this locale was high. This study provides new information about the natural history of this bee species, which is an important pollinator of both crops and native plant species.     

Estimating population features of the anomuran crab Petrolisthes armatus (Porcellanidae) in a remaining and impacted mangrove area of the western Atlantic

This study evaluated biological aspects of Petrolisthes armatus inhabiting a remaining but disturbed mangrove area of Brazil. Samples were taken from March 2005 to July 2006, during low tide in the rocky-shore region. The size frequency distribution for all the individuals collected was bimodal. The sex ratio obtained was not different from 1:1, and the population was classified as standard. A higher reproductive ratio and earlier ovigerous conditions were found in relation to another southern population; these can be hypothesized as adaptations to life in a stressed environment. Even though the population living in Araçá has been subject to an environment frequently disturbed by human-produced pollutants, our results show no sign of negative effects on reproductive stages, recruits or members of the population in general. The population profiles of P. armatus show some peculiarities when compared to other populations inhabiting non disturbed environments.     

Taxonomic review of the Amazonian millipede genus Parastenonia Hoffman, 1977 and description of a new species from iron-ore caves (Polydesmida: Chelodesmidae)

ABSTRACT

The Amazonian genus Parastenonia Hoffman, 1977 is here revised. The species P. carajas sp. nov. is described from Brazilian iron-ore caves and P. aurae (Schubart, 1947) is considered junior synonym of P. parae (Cook, 1895). In addition, the known geographic distribution of the genus is presented with the inclusion of new occurrence data.

http://www.zoobank.org/urn:lsid:zoobank.org:act:CCBEED10-DCB4-48C9-A71D-CED3462DD72A