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Archive for the ‘Spiders’ Category

The Golden Orb-Weaving spider – Nephila clavipes (Linnaeus, 1767) of the family Nephilidae – is known from USA to Argentina. In Costa Rica, it occurs in lowland and premontane tropical rain forests. Females make large aerial webs in which they usually occupy the centre. Orb-web spiders are effective predators and can easily subdue prey that is significantly larger and heavier than the spider (see on photo).

Two females of Nephila clavipes with prey; Costa Rica.

Two females of Nephila clavipes with prey; Costa Rica.

One of the most peculiar characteristic of this species, as well as of other Nephila species, is an extreme sexual size dimorphism, where dwarf males can be many times smaller and lighter than the females (see on photo). Numerous hypotheses have been proposed to explain the factors that may give rise to such size dimorphism in spiders. Some of them are briefly discussed here.

In the case of Nephila, it is argued that that large size in females could be driven by selection on female fecundity (= the potential reproductive capacity), acting to increase the number of offspring produced. With the high level of juvenile mortality, the production of larger numbers of offspring is crucial for survival of the species. Thus such size dimorphism is almost always due to female gigantism rather than male dwarfism.

As was demonstrated for some African species [e.g., Nephila pilipes (Fabricius 1793)], females continue to grow after reaching maturity. The females mature at varying body sizes and instars and then continue to grow by molting the entire exoskeleton except their copulatory organs (=genitalia). Apparently, this is why in Costa Rica Nephila clavipes is represented by mature females of markedly variable body sizes (although, to date, a post-maturity molting has not been described for this species).

In a short video presented below (courtesy of Alex Villegas, Costa Rica) it is shown how a dwarf male of Nephila clavipes is approaching a giant female in its attempts to mate, alas unsuccessfully this tiem. Indeed, the male is to be careful in order not to be mixed up by the female with a potential prey.

Further reading:

Kuntner, M. & Coddington J.A. 2009. Discovery of the largest orbweaving spider species: the evolution of gigantism in Nephila. – Plos; DOI: 10.1371/journal.pone.0007516

Kuntner M., S. Zhang, M. Gregorič, and D. Li. 2012. Nephila female gigantism attained through post-maturity molting. – Journal of Arachnology 40(3):345-347. DOI: http://dx.doi.org/10.1636/B12-03.1

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On the second day of our field trip to Iceland, we visited the interesting site lying in the southern municipality of Reykjavik, called Garðabær, which literally means ‘Garden Town’. We walked around the beautiful Lake Urridavatn surrounded by boggy meadows full of sedge, dwarf bushes (like blue berry) and cotton grass (see on the photo).

Boggy meadow with cotton grass (left) and the blue berry bush (right) near Lake Urridavatn in Iceland

Boggy meadow with cotton grass (left) and the blue berry bush (right) near Lake Urridavatn in Iceland

On the meadow side of the path to the lake we found a plastic cup thrown by someone a few days ago. Incidentally, the cup, which was partly filled with rain water, became a deadly trap to insects and spiders. Having inspected the content of the cup I found two specimens of crab spiders (Xysticus sp.; male and female), one specimen of the ground beetle (family Carabidae) and one harvestman (family Phalangiidae). So, the cup ‘worked’ exactly in the way as true pitfall traps (see also here) that are used by scientists for ecological surveys. A poor thinking or maybe carelessness of someone who threw this plastic cup away instead of dropping it into a waste bin resulted in some casualties of minibeasts. Throwing a plastic cup (or any unwanted plastic item) away is hardly seen as a great deal or an action causing any threat to wild life. However, my short and simple story seems to say otherwise. In simple words, it reminds us that recycling waste is essential to both natural environment and humans, minimizing an unnecessary risk of damage to the environment and helping out our planet be a better place to live in. More about recycling can be seen here and here.

The plastic cup that became a deadly trap to a number of minibeasts near Lake Urridavatn in Iceland. See also a short video below.

The plastic cup that became a deadly trap to a number of minibeasts near Lake Urridavatn in Iceland. See also a short video below.

 

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Harvestmen (Opiliones) represent a diverse group of arachnids, with more than 6,500 species described worldwide; see here for a complete list. Everyone seems to be familiar with these animals which have an oval/round body and long-long thin legs; this why their English common name: ‘daddy-long-legs’. However, there are short-legged species as well. The harvestman fauna of the La Selva Natural Reserve (Costa Rica) consists of about 40 recorded species, half of which remain unnamed yet (Proud et al., 2012).

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A group of harvestmen (Prionoistemma sp.) on tree trunk, La Selva, Heredia, Costa Rica.

One of the interesting and commonest species of La Selva is Prionoistemma sp. (family Sclerosomatidae). This species has a small round pink body with black lateral spots and very long legs. Harvestmen usually spend the daytime on the trunk of large trees, at their bases, while during the night time they actively walk up and down the trunk and also over the undergrowth vegetation. When someone approaches them, the creatures begin to shake all over on their thin legs becoming almost invisible for a spectator.

The majority of harvestmen are omnivorous feeding on a variety diets, and seem to be effective predators. On the short video given below it is seen that this Prionoistemma male is feeding on a jumping spider (family Salticidae). The jumping spiders are very active and effective diurnal predators, with sharp colourful vision. Very few predators are capable of capturing them. How on the earth could this harvestman have seized the jumping spider remains a mystery. I’ve never observed this myself earlier.

Reference:

Proud D. et al., 2012. Diversity and habitat use of Neotropical harvestmen (Arachnida: Opiliones) in a Costa Rica rainforest. – ISRN Zoology, doi: 10.5402/2012/549765

 

 

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On the second day of our staying in San Jose (11th June), we had a chance to visit the Pre-Columbian Gold Museum (Museo del Oro) – the archaeological museum organized by the Central Bank of Costa Rica in 1950. This Museum hosts temporary exhibitions on a variety of themes and also houses a remarkable permanent gallery of pre-Columbian gold objects crafted between 300 A.D. and the 16th century, the time of the first contact with Europeans.

Objects manufactured during this period present a mixture of styles generated by contact and exchange with neighbouring regions such as modern central Panama and modern Colombia. Objects exhibited in the Museum were used as trade goods between regions and as ritual ornaments and funerary offerings. Many figures depict men with animal masks, apparently pointing to some superhuman qualities of those leaders who wore them. There are many animal figurines, including those of frogs, which are especially numerous, jaguar, alligators, bat, and others. Of the arthropods, only figurines of butterflies, crustaceans and spiders were displayed.

Pre-Columbian Gold Museum, San Jose, Costa Rica

Pre-Columbian Gold Museum, San Jose, Costa Rica

Butterflies
In traditional stories of the indigenous people of Talamanca, the butterfly is a woman who serves as an intermediary between the natural and supernatural worlds. This role of messenger and special being is reflected in the criteria used to select the woman who can be trained to carry out ritual tasks. They must have positive traits such as honesty, bravery and dedication.

Butterfly-shaped pendants, with the body representing alligators - the common practice of combining animals within a single object.

Butterfly-shaped pendants, with the body representing alligators – the common practice of combining animals within a single object.

Crustaceans
During the pre-Colombian period the marine environment was intensely exploited for edible species such as shrimps, crabs, lobsters and fish. Figurines of all these animals were manufactured as shown below.

Crab-shaped pendants.

Crab-shaped pendants.


Lobster-shaped pendants and circular pectoral (in the centre). The pectoral was a symbol of high rank among pre-Columbian people.

Lobster-shaped pendants and circular pectoral (in the centre). The pectoral was a symbol of high rank among pre-Columbian people.

Spiders
I could not photograph the autentic gold spider-shaped pendant in the Museum, and here is a photo of nice replica manufactured by a contemporary artists from the open-air market near the National Museum of San Jose.

Replica of the spider-shaped bell, with a hanging smaller bell.

Replica of the spider-shaped bell, with a hanging smaller bell.

The explanatory text provided above is based on the captions displayed in the Museo del Oro and the book by P. Esquivel (2012) ‘Extraordinary pieces from the Pre-Colombian Gold Museum’

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On June 10th, 2014, I visited the National Institute of Biodiversity in San Jose, Costa Rica (INBio, Instituto Nacional de Biodiversidad) and worked with the spider collections. The main aim was sorting out specimens of the jumping spider genus Lyssmanes (Salticidae) for its further taxonomic study. It is a collaborative project with the INBio’s arachnologist Carlos Viquez.

INBio is a private non-profit organization, founded in 1989, that works on the inventory of Costa Rican biodiversity. This institution carries out research on microorganisms, plants, insects and other animals. Since its foundation, INBio has discovered more than 2,700 species new to science. The institution retains large natural history collections numbering 4-5 million specimens and thousands of species. Here are a few photos resulted from my visit to INBio.

Cabinets with the spider collections, INBio, San Jose, Costa Rica

Cabinets with the spider collections, INBio, San Jose, Costa Rica

Carlos Viquez, the curator of the arachnid collections, INBio, San Jose, Costa Rica

Carlos Viquez, the curator of the arachnid collections, INBio, San Jose, Costa Rica

A drawer of fruit beetles from Costa Rica, INBio, San Jose, Costa Rica

A drawer of fruit beetles from Costa Rica, INBio, San Jose, Costa Rica

Slide collection of INBio, San Jose, Costa Rica

Slide collection of INBio, San Jose, Costa Rica

The large herbarium of INBio, San Jose, Costa Rica

The large herbarium of INBio, San Jose, Costa Rica

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Spider ID workshop at the Manchester Museum (Oxford Road, Manchester M13 9PL) on Saturday 2nd February, provisionally 10am – 4pm.

This workshop is for beginners and attendance at the workshop is free.

This course will introduce the common families of spider that can be found in the UK. Attendees will be shown basic spider anatomy and how to identify spiders to family level and also some easy spider species.

We will use microscopes and the recommended ID guides (provided, although some sharing may be necessary).

We may have some live spiders to examine, but the emphasis with the microscopes will be on how to identify preserved specimens in alcohol.

This is necessary to clearly understand the anatomy and features used in identification (which when familiarised can often be viewed with a hand lens on live spiders in the field).

Space is limited to 10 attendees.

Please contact Philip Baldwin, North West Regional Coordinator, to book your place on this workshop, preferably by email with your contact details; Mobile: 07585 606148, email philip.baldwin900@ntlworld.com; or Dmitri Logunov, the Curator of Arthropods (email: dmitri.v.logunov@manchester.ac.uk).

 Other events run by the British Arachnological Society can be checked upon online at: http://wiki.britishspiders.org.uk/index.php?title=Events,_etc.

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Some people may think that natural history museums deposit only old, historically and/or scientifically important collections. Although this is true, museums also continue to acquire new materials coming to them in various ways. In order just to give visitors an idea about how new collections can be acquired, here is a very brief report on new acquisitions made by the Manchester Museum’s Entomology department during the last five years, from January 2008 to December 2012.

A total of 66 acquisitions of 17,477 specimens have been received, as follows:

1.    Fieldwork (by the curator): 3 acquisitions of 368 specimens.

2.    Enquire-based acquisitions (usually via the identification service we provide): 10 acquisitions of 61 specimens.

3.    Acquisitions related to the public events that we support (Bioblitzes and others): 5 acquisitions of 112 specimens.

4.    Exchange: 1 acquisition of 121 specimens.

5.    Donations: 47 acquisitions of 16,815 specimens.

 Of the aforementioned donations, the largest single one was the spider collection of Dr. Eric Duffey (Norfolk) from Britain, France and Spain acquired in July 2011, which alone consisted of more than 6,000 sample tubes containing 12,545 specimens. The collection has a high scientific value and started being intensively used both for research and for teaching.

Some donations are quite unusual. For instance, a set of three trays apparently produced in Brazil and received in July 2011. Each tray contains a selection of 12 to 21 showy tropical butterflies incorporated inside its bottom, with a nice Morpho-butterfly in the centre (see photo). The trays were first given to us for the identification of butterflies, which we did, and then were simply donated to the Museum.

Unusual Trays acquired in July 2011.

Unusual Trays acquired in July 2011.

Although the majority of newly acquired insect or spider collections represent an essential resource for taxonomic research, many specimens can also be used (and are used) in various Museum’s educational programmes or temporary/permanent exhibitions. A new permanent Museum’s exhibition called ‘Nature’s Library’, which is due to open in April 2013, will be specifically devoted to our large natural history collections hidden behind-the-scenes and to why these collections are here and how are they used. Do not miss out the opening date (check out the Museum’s site regularly).

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