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.     

Cohabitation of males and juvenile females: a prevalent mating tactic of spiders

Cohabitation, a mating tactic in which males remain with juvenile females until they moult and mature, is shown to be common among spiders. Records are given for 161 species in 74 genera and 15 families. Records were obtained for 100 species of cursorial spiders (45 genera, eight families) and 71 species of web-builders (33 genera, 11 families). Cursorial species cohabit in nests, whereas web-builders cohabit either in the open on their webs or in nests in or near their webs. Duration of cohabitation in nature and in the laboratory was recorded for 12 species. An apparent tendency for web-builders to cohabit longer than cursorial species is discussed. The longest cohabitation occurred in three web-building species (Inola amicabilis, Inola subtilis: Pisauridae; Portia fimbriata: Salticidae) in which males remained with females two moults from maturity, and juvenile, as well as adult, males cohabited with juvenile females. The prevalence of cohabitation in the Salticidae, the family that provided the largest number of examples (72 species: 33 genera), is discussed in relation to current hypotheses about salticid phylogeny.     

A preliminary study of nest structure and composition of the weaver ant Polyrhachis (Cyrtomyrma) delecta (Hymenoptera: Formicidae)

Polyrhachis weaver ants build their nests from vegetation bound together using silk produced by their larvae. Here we provide a pilot study of the composition and the physical structure of three arboreal silk nests of Polyrhachis (Cyrtomyrma) delecta based on examination of three colonies. We found broadly similar nest architecture and size of the nests with each containing six or seven identifiable chambers, and describe the distribution of ants of different castes and life stages between them. We also note the construction of silk ‘girder’ structures, which spanned larger chambers, and we hypothesize that these provide additional strength to the internal nest structure. This study highlights the importance of more detailed investigation of the internal nest structure and composition in Polyrhachis, and other weaver ant species, which will help to develop our understanding of this specialized form of nest construction and nesting habits in a diverse group of ants.     

Ecology and behaviour of the weaver ant Camponotus (Myrmobrachys) senex

Abstract

Weaver ants use silk produced by their larvae to build their nests. This behaviour is one of the more notable instances of social cooperation in animals; however, there are few studies of Brazilian species. This study investigated the ecology, natural history and behaviour of the weaver ant Camponotus (Myrmobrachys) senex in Brazil and showed that the weaver larvae have a fundamental function in nest building. The nests were always arboreal (one nest/plant), with a round form, beige in colour, and with leaves and shoots adhered to the silk nest. The average size was 34.24 cm and the average weight was 163.87 g; nests contained up to 50,000 individuals and several queens. Fusion and fission of colony parts were observed for C. senex. Worker ants were frequently observed feeding on honeydew, fruits and insects; and defended their territory. We suggest that C. senex larvae could be considered an effective caste, valuable in nest construction.     

Two new species of Hymenoepimecis (Hymenoptera: Ichneumonidae: Pimplinae) with notes on their spider hosts and behaviour manipulation

The wasp genera included in the Polysphincta genus-group develop exclusively as koinobiont ectoparasitoids of spiders, an unusual pattern within Hymenoptera. All known species of Hymenoepimecis attack orb-web spiders and Hymenoepimecis argyraphaga was previously described inducing a sudden modification of its host's web-building behaviour. Information on parasitoid–host interactions and even on host identities for most members of the genus-group, however, remain scarce. In this study we describe two new species of Hymenoepimecis and present information on their hosts, spiders of the genera Leucauge (Tetragnathidae) and Manogea (Araneidae). Cocoon webs of both host species are distinct from their normal webs. The modified cocoon web of Leucauge roseosignata constructed under the influence of Hymenoepimecis japi sp. nov. is very similar to the cocoon web described for Leucauge argyra. It is composed of three axes, including several radial threads each, and a hub used by the larva to attach the cocoon's suspension line. Spiral viscous threads, present in normal webs and in webs of parasitized spiders carrying larvae in the initial instars, are absent in cocoon webs. In the cocoon web of Manogea porracea the horizontal sheet is poorly structured and the cocoon is attached far from the spider's normal resting position, in an area composed of a densely tangled structure.     

Rare fishes from the Clyde sea area

Summary

The swarming flights of 23 species of termite were observed at three localities within Brazil and data collected on the periodicity of swarms, the predators which attach the exposed termites and the defensive behaviour of the three castes of termites.

The principal predators on termites during swarming were ants at ground level and birds in the air. The defensive behaviour of workers and soldiers effectively protected the termite alates from terrestrial predators, but only the low level of light at dawn and dusk protected them from aerial predators.

Most of the termites released their alates at the beginning of the rainy season, either at dawn or at dusk and protected them from grounded predators with a ‘blanket’ cordon of workers and soldiers.

Three species of the subterranean, soldierless Anoplotermes constructed special launching towers for the release of alates and protected them from predation with these structures. Armitermes euamignathus and Cornitermes cumulans also built launching structures on their nests for alates, but showed the ‘blanket’ behaviour of most termitids in their defence.

The towers constructed by the three species of Anoplotermes indicated, by their distribution and number, the density and approximate size of the subterranean colonies which built them. A mean density of 240 nests ha^-1 and 258·24 termites m^-2 was estimated for Anoplotermes sp I.     

The food web of parasitoid wasps and their non-phytophagous fly hosts in birds' nests (Hymenoptera: Chalcidoidea,and Diptera: Cyclorrhapha)

We present a food-web study of the parasitoid wasps and their fly hosts found in the nests of cavity-nesting songbirds. This birds' nest parasitoid web is different from all parasitoid webs studied comprising exclusively non-phytophagous host species. A total of 490 nests were examined for host occurrence, abundance and parasitism rates. Thirty-two species of potential hosts and 10 species of parasitoid wasps were recorded in nests from 25 sites in northern Germany and from two additional sites in south-western Germany. Most of these species were rare and unspecialized. The only very common parasitoid was Nasonia vitripennis (Chalcidoidea: Pteromalidae). The records of 14 regular host species from northern Germany, which are connected to all 10 parasitoid species, were used for further calculation of food-web statistics. The parasitoid communities in birds' nests were compared with other known parasitoid communities. The birds' nests exhibited a lower species richness compared with communities of phytophagous hosts, but showed similarities with communities of necrophagous or coprophagous hosts, or of parasitoid hosts. The parasitism rate was comparable in all host–parasitoid-systems, supporting the idea that the parasitism rate is independent of species richness.     

Trolling for water striders: active searching for prey and the evolution of reduced webs in the spider Wendilgarda sp. (Araneae,Theridiosomatidae)

Wendilgarda sp. builds unusually simple webs attached to the surface of water. The simplest design consists of a single vertical line with sticky material near the bottom that is attached at the top to a single horizontal line and at the bottom to the water surface. The spider usually sits immobile waiting for prey as the sticky line skates erratically across the surface of the water, but some spiders actively dragged their webs back and forth across the water. The web's simplicity is apparently derived with respect to the webs of other Wendilgarda species, as spiders sometimes made more complex webs similar to typical Wendilgarda webs. The simplicity of W. sp. webs may be causally related to two other unusual traits: extreme variability in web design and construction behaviour and web manipulation behaviour; and construction of prey capture webs with sticky lines by mature males, confirmed here for the first time in a confirmed member of an orb-weaving family. Some behavioural innovations in Wendilgarda, such as the attachment of a short segment of non-sticky silk to the water surface just prior to laying each segment of sticky line, may represent blocks of behaviour that have been shifted temporally in the web construction sequence.     

Predation on eggs of Schneider’s dwarf caiman,Paleosuchus trigonatus (Schneider, 1807), by armadillos and other predators

Nests of Schneider’s dwarf caiman, Paleosuchus trigonatus, were located in the forests around three streams that drain into the Xingu River, Brazilian Amazonia, in October 2014. Camera traps were installed at the edge of four nests to document predators and female parental care. At two nests, females unsuccessfully defended their nests against one or more giant armadillos, Priodontes maximus, and nine-banded armadillos, Dasypus novemcinctus. Both armadillo species responded to the attack by fleeing and returning on the opposite side of the nest by going around the tree under which the nest was located. Giant armadillos have never before been recorded consuming caiman eggs and their diet has been described as consisting mostly of ants and termites. Another species of armadillo, Cabassous unicinctus, was also registered digging into a nest and probably consuming eggs, though it is generally considered to be primarily insectivorous. A tayra (Eira barbara), lizard (Tupinambis teguixin) and coati (Nasua nasua) were also registered taking eggs from nests during the day, but we obtained no registers of nest defence by caimans during the day. The three nests were attacked after 60 days of incubation, when the eggs were well developed.     

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).     

Dipteran infestation of loggerhead (Caretta caretta) and green (Chelonia mydas) sea turtle nests in northern Cyprus

This paper describes dipteran infestation of loggerhead (Caretta caretta) and green (Chelonia mydas) sea turtle nests in northern Cyprus in 1996 and 1997. Insect larvae were collected from infested nests, reared to adulthood and identified to species. A minimum of 13.4% (1996) and 17.4% (1997) of loggerhead turtle nests and 3.3% and 20.7% of green turtle nests were infested in 1996 and 1997, respectively. Eleven dipteran species were found infesting turtle nests with one species (Sarcotachina aegyptiaca) being dominant. Gross estimates, utilizing the speeds of development for three species of sarcophagid showed that infestation was taking place differentially between the two turtle species. Various aspects of the effect of dipteran infestation on marine turtle nests in northern Cyprus and recommendations for future investigations are discussed.     

The diet of the Eleonora’s falcon (Falco eleonorae) in the Aegean archipelago (Greece)

ABSTRACT

In the present study we investigated the diet of Eleonora’s falcons in Greece and assessed the regional dietary pattern of 16 breeding colonies of the Aegean. Overall 224 nests were visited and a total of 8067 prey items were collected which contained two mollusca classes, seven insect orders, one reptile family, two mammalian taxa and at least 54 avian species. Cicadas were the most common insects found in pellets (45.1%) followed by flying ants (34.8%) and beetles (15.8%) while just 20 species (33.3%) accounted for over 90% of the avian prey items identified in bird remains dominated (>50%) by the Willow Warbler (Phylloscopus trochilus), the Red-backed Shrike (Lanius collurio) and the Whitethroat (Sylvia communis). Insect feeding peaked in late August (39.8%) and late September (20.8%), whereas bird remains built up in falcon nests from mid-August onwards, culminating in late September (57.2%) and declined abruptly afterwards. Overall the falcons’ diet diversity increased as the breeding season progressed and from the north towards the south Aegean. The avian prey species richness was negatively influenced by the distance of the colonies from the mainland and the weather conditions during September which coincides with the fledgling period of the young and the autumn peak of passerine migration.     

Population variation of web-invading spiders (Theridiidae: Argyrodes spp.) on host webs in Guam,Mariana Islands,Micronesia

Most Argyrodes spiders live in the webs of other spiders as kleptoparasites, stealing food from the host and scavenging small prey from the web. We observed three species of Argyrodes from the Micronesian island of Guam to learn (1) if Argyrodes species differ in their use of host-species webs, (2) whether some Argyrodes species occur more often in certain habitats, (3) whether population size of Argyrodes is a function of web size, and (4) how the presence of congeners affects population size on a web. Argyrodes lived most often in the large, long-lasting orb webs of Argiope appensa and Cyrtophora mollucensis, and, rarely, in the smaller, less durable orb webs of Neoscona spp. and Leucauge spp. Argyrodes argentatus and Argyrodes sp. A frequently co-occurred in Argiope webs, but A. argentatus was more common in beach strand and open disturbed habitats, while Argyrodes sp. A was more common in shaded native forest. The abundances of A. argentatus and Argyrodes sp. A in Argiope webs and the abundance of Argyrodes sp. B in Cyrtophora webs were positively correlated with the areas of the webs' prey-catching surfaces. The abundance of A. argentatus was inversely proportional to that of Argyrodes sp. A on Argiope webs and to that of Argyrodes sp. B on Cyrtophora webs, suggesting interspecific avoidance.     

Web decoration polymorphism in Argiope Audouin, 1826 (Araneidae) spiders: ontogenetic and interspecific variation

Spiders in the genus Argiope commonly include curious silk structures, termed web decorations or stabilimenta in their webs. Whilst interesting ontogenetic and interspecific variation in both the form and frequency of web decorations has been documented, to our knowledge this is the first study to compare this variation across a number of decorating species. Here we show that two sympatric species A. picta and A. aetherea construct different forms of web decorations as adults and that A. picta decorates at a higher frequency than A. aetherea. Furthermore, this difference in decoration frequency may be related to the different decoration forms (linear or cruciate) across this genus. We also show that native bees responded significantly more quickly to cruciate decorations than to linear decorations. Here we argue that consideration of the different decoration forms and the frequency at which spiders adorn their webs may help illuminate possible context‐dependent functions for these curious structures.     

Orb‐web spiders (Araneae: Araneomorphae; Orbiculariae) captured by hunting‐wasps (Hymenoptera: Sphecidae) in an area of Atlantic Forest in south‐eastern Brazil

Members of two hunting‐wasp families, Pompilidae and Sphecidae, are among the major predators of orb‐web spiders. In this study, we collected paralysed spiders from natural nests and trap‐nests provisioned by sphecids in an area of Brazilian Atlantic Forest, and compared these data with the composition of species collected by visual searching during one year. Prey preferences were analysed based on the relative abundance of spider species, their size and web characteristics. We also compiled a list of orb‐weavers captured by four sphecid genera reported in 40 other studies. A large number of prey was obtained from natural nests of Trypoxylon (Trypargilum) albonigrum in Parque Estadual Intervales, especially species of Eustala, Parawixia, and Araneus (Araneidae). Other prey, stored in trap‐nests by T. lactitarse and unidentified hunting‐wasp species, included Nephila (Tetragnathidae), Parawixia, Ocrepeira, Mecynogea, Acacesia (Araneidae), and other spider species that were less abundant. All the species that were heavily preyed upon had a relatively lower abundance in our samples of prey availability. The range of body sizes of spiders captured by Trypoxylon in our study area include the size of some abundant orb‐weavers always absent in their nests. These results indicate that factors other than abundance in the field and the spider's size influence prey selection or susceptibility to attack.     

Host–parasite relationships and life cycles of cuckoo wasps in agro-ecosystems in Argentina (Hymenoptera: Chrysididae: Chrysidini)

Chrysididae is a diverse group of parasitoid/cleptoparasitic wasps; however, host–parasite relationships and life cycles of few species have been studied. Nests of different wasp and bee species were obtained during a trap-nesting programme, in the Pampean region. Some of these nests were parasitised by cuckoo wasps females of Caenochrysis taschenbergi (Mocsáry), Chrysis boutheryi (Brèthes), C. saltana Bohart, C. sp. 1 (ignita-group), C. sp. 2 (ignita-group), Neochrysis lecointei (Ducke), Pleurochrysis ancilla (Buysson) and P. lynchi (Bréthes). This paper reports new data about host–parasite relationships and life cycles for these species. Multiple parasites (from one species or from different families of insects) emerged from single cells of some parasitised nests: from each host cell parasitised by species of Pleurochrysis, two adults emerged successfully, information previously unknown for the genus; and in three cases of cells parasitised by C. boutheryi, two adults successfully emerged from a single cell; in two cases both individuals were chrysidine, and in third one was chrysidine and one Leucospis pulchripes (Leucospidae).     

Asynchronous reproduction in three species of crocodilians in south-eastern Amazonia

We studied reproduction of three species of crocodilians, Paleosuchus trigonatus, Caiman crocodilus and Melanosuchus niger, in the Xingu River, near the Belo Monte hydroelectric dam. The periods of laying and hatching of eggs were estimated for each nest before (2013–2014) and after (2016–2017) the river was dammed and the reservoir was formed. Nesting of the three species occurred between August and December, but was largely asynchronous; nest construction peaked in September for P. trigonatus, October for M. niger and November for C. crocodilus. Reservoir filling had little effect on the laying period of any of the species. Nests of P. trigonatus and M. niger were always within 0–12 m of the bank, whereas nests of C. crocodilus, which nests later in the season when flooding is more likely, were up to 100 m from the nearest water body. There was no relationship between distance from water and the number of eggs in nests, suggesting that larger and presumably more experienced females do not lay at different distances from the bank in any of the species.     

Redescription of Retilaskeya horrida (di Monterosato, 1874) comb. nov. and a re-evaluation of the taxonomic affinity of the genus Retilaskeya (Caenogastropoda: Triphoroidea)

The family Cerithiopsidae H. Adams and A. Adams, 1853 is distributed worldwide, and comprises around 800 extant species divided into ~40 genera. The most speciose genus within the family is Cerithiopsis Forbes and Hanley, 1850, a taxon currently used as a general receptacle rather than as a proper phylogenetic lineage. We hereby redescribe the rare species Cerithiopsis horrida di Monterosato, 1874, review its nomenclature, known material, and distribution as well as figure the entire protoconch, operculum, and radula for the first time. Our results highlight extreme differences between ‘Cerithiopsis’ horrida and the Cerithiopsis type species Cerithiopsis tubercularis (Montagu, 1803) and strong morphological and radular similarities with species belonging to the genus Retilaskeya Marshall, 1978. A wide discussion lists several taxa that might be ascribed to the same group of species, which presumably constitute a different worldwide lineage. Pending relevant molecular phylogenetic studies of the Triphoroidea Gray, 1847, for morphological conformity we suggest transferring ‘Cerithiopsis’ horrida to the genus Retilaskeya, and the same action is presumably appropriate for its possible sister species ‘Cerithiopsis’ leopardus Rolán and Gori, 2013. Finally, Retilaskeya better conforms to Newtoniellidae Korobkov, 1955 than Cerithiopsidae.     

Assembly of Myrmelachista Roger (Formicidae: Formicinae) in twigs fallen on the leaf litter of Brazilian Atlantic Forest

The nests of Myrmelachista are found in tree trunk cavities and branches. The biology of these arboreal ants is still relatively unknown. We investigated the nesting behaviour of this genus in fallen dry twigs in the Atlantic rainforest of southeastern Brazil. Physical characteristics of the nests, colony demographics, presence of breeders and ant worker sizes were recorded. Samples were collected weekly for 12 months, along open, sunny and undisturbed trails within forest remnants. In all, 202 nests were collected and six species were recorded. Myrmelachista ruszkii had the highest population of immatures and the greatest number of nests found. Myrmelachista nodigera had the smallest workers, was the least populous and the colony was housed in the finest branches. These results expand the current knowledge about the diversity and biology of Myrmelachista in the Brazilian Atlantic forest, and describe polydomic nests and competitive behaviour of M. ruszkii.     

Biology and life history of the araneophagic assassin bug Stenolemus bituberus including a morphometric analysis of the instars (Heteroptera,Reduviidae)

Stenolemus bituberus is an araneophagic “assassin bug” (Heteroptera; Reduviidae; Emesinae) that typically is found living in spider webs. We documented the life history of S. bituberus in the field for 13 months, determining its developmental phenology and microhabitat characteristics as well as describing its mating and predatory behaviour. We also included a morphometric analysis of the instars. Our study revealed that S. bituberus is univoltine with five juvenile instars. Although S. bituberus is found in the webs of spiders from a wide range of genera, it is found most commonly in the webs of Achaearanea, Badumna, Pholcus, and Stiphidion. Multiple juveniles often were found on a single web, but adults tended to be more solitary. Stenolemus bituberus appears to have two distinct hunting strategies: “stalking”, in which they slowly approach the spider, make contact and then strike; and “luring”, in which they attract the spider within range by manipulating the silk with their legs.