The Arachnids of Tortuguero, Costa Rica: Part One — Spiders
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In the first part of this article, I covered my favourite arachnids—the scorpions. Here I will cover spiders. Wherever you may be reading this, chances are that you are pretty close to a spider of some description. If you happen to be reading this at the Cano Palma research station near Tortuguero, Costa Rica, then chances are you can see several spiders from where you are sitting and at least one of them is as large as your hand.
The only thing more impressive than the vast number of spiders to be found in the area is the startling variety of species. Nowhere was this more apparent than in the web spinning spiders (Figure 1). Upon arriving at the dock of the research station, we were greeted by a number of Argiope (Fig 1b, 1g) and Nephila (Fig 1c) spiders that had established themselves within the framework of the roof over the dock. The variety of web patterns among the Argiope species was notable, as was the variation in the colouration and adornment of the spiders. Though nothing was identified to species, it was apparent that there was a great degree of diversification in this area.
Another web spinner was to be found on subsequent nights, deep within the forest surrounding the station. The ogre-faced spider (Dinopidae) (Fig 1f) spins a rectangular web, which it throws over its prey to capture it. When disturbed the spider abandons its net, which remains suspended in midair by several strands of supportive webbing, and hurries along one of the supporting strands. There, it straightens itself out, with its legs stretched along the single strand of silk, and looks quite like a leaf that has decayed and left only a few raggedy veins behind.
Not all spiders build webs, of course, and more mobile spiders with well represented on our journey. Ctenid spiders such as Cupiennius (Fig 2h, 2i) were by far the most apparent, seeming to inhabit every vertical surface—including those within the station. Some of the specimens we saw had leg spans well over 15 cm (6 inches) and were bright orange—impressive spiders by any measure. At first we thought that the variation in colouration we saw might be indicative of species, but a witnessed mating (Fig 2h) would suggest that at least some of it might be dimorphism within species.