Costa Rica fieldcourse 2014 – Harvestmen

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).

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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Costa Rica fieldcourse 2014 – Leafcutter Ants

At the La Selva Biological Station (Costa Rica), where we are now and where students are doing their individual research projects, there are lots of Leafcutter Ants.
‘Leafcutter ants’ is a group name for 47 species of the two genera Atta and Acromyrmex occurring in Mexico, Central and South Americas. Leafcutter ants form very large and complex underground colonies containing up to eight million individuals. The central mouth of such colonies can reach 30m in diameter. The ants cut fragments of fresh vegetation (leaves, flowers and grasses) and transport them to their nests. The fragments are then used as the fertilizer for cultivating special fungi, the main diet of the ant larvae. The adult ants feed on leaf sap. The trails used by ants for carrying leaves back to the colony often look like the paths trampled down by large animals (see the photo below).
What is interesting, many ants carry not only leaf fragments but also smaller ants sitting on them (see on videos). It is assumed that small, ‘hitchhiking’ ants protect foraging ants from parasitic flies (Phoridae), and may also play a part in the cleaning and preparation of leaves for the use as fungus substrate.
As some Atta species are capable of defoliating an entire citrus tree in less than 24 hours, sometime the ants may become a serious agricultural pest, defoliating crops and damaging roads and farmland with their nest-making activities.
For more general information on the Leafcutter Ants, see here and here.

Leafcutter Ants (Atta sp.) on the trail, La Selva Biological Station, Costa Rica

The large trail of Leafcutter Ants (Atta sp.), La Selva Biological Station, Costa Rica

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Costa Rica fieldcourse 2014 – Observing bees

One of the most interesting groups of insects, ideal for student projects during a fieldcourse in the American tropics, is the Orchid Bees (Apidae: Euglossini). These are beautiful bees of which most species have metallic iridescent colour of various hues of green, blue or bronze, although there are hairy and black groups. Other conspicuous features of these bees are the long tongue, which is often longer than the body length, and the remarkably swollen hind tibia of the males. Male orchid bees play a key role in orchid pollinations, this is why their name. There are 66 recorded species of orchid bees in Costa Rica, of about 200 species known worldwide.
Male orchid bees can easily be lured with odour baits, for instance, clove or eucalyptus oils, and thus be closely observed by a student. Here are a couple of photos and two short videos showing the males of Euglossa bees in action.

Another interesting group of bees commonly seen in tropical America is the Stingless Bees (Apidae: Meliponini). These are close relatives of the Orchid Bees, but highly eusocial – in other words, living in large family groups (up to 100,000 adult individuals depending on a species) containing two main casts: a queen laying eggs and her daughters, the workers that cooperate in rearing the brood and maintaining the nest; exactly as it happens in the hives of the well-known Honey Bee (Apis mellifera). Many regional hotels in Costa Rica have special feeders set up for hummingbirds so than visitors can observe them virtually from the windows of their rooms or from hotel balconies. The same feeders, which are filled with sweet nectar-like liquid, also attract lots of Stingless Bees. On the following photos and a short video below you can see and watch a group of Trigona bees, apparently of the species Trigona corvina, observed on a hummingbird feeder near the hotel ‘Rancho Naturalista’ in Turialba region of Costa Rica. The second image and video shows the Stingless Bees of an unknown species near their nest at La Selva Biological Station in Costa Rica.

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Costa Rica fieldcourse 2014 – Pre-Columbian Gold Museum

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

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.

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.

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.

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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Costa Rica fieldcourse 2014 – visit to INBio

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

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

Slide collection of INBio, San Jose, Costa Rica

The large herbarium of INBio, San Jose, Costa Rica

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