The Arachnids of Tortuguero, Costa Rica: Part One — Scorpions
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"Dave! Scorpion!" My friend Dan shouted out to me from where he knelt by a log. I stopped focusing my camera on a flower and had taken two steps before I reminded myself that I was at COTERC's Cano Palma research station near Tortuguero, Costa Rica and this was Fer-de-lance (Bothrops asper) territory. Keeping an eye on where I was stepping, I ran over and knelt down by Dan. There, lying on the partly decomposed log that Dan had broken open, was a yellow scorpion almost 4 in [10 cm] in length. "Hey, there's another one," he added. Sure enough, a slightly smaller and darker scorpion was lying in the log only inches away. It was then that I realized I had two scorpions and only one vial. Fortunately, my girlfriend and traveling companion Tamara had a sandwich bag with her and both specimens were quickly captured and identified as Centruroides limbatus. The yellow specimen was obviously male, with its extended metasomal segments and lean body shape, while the dark specimen proved to be a female. One can only speculate as to whether or not they had been breeding some time prior to their capture.
Several more Centruroides limbatus were found throughout the one week trip. All were found on or near the ground, in areas where there was abundant cover. In later conversations with hobbyists, there was some consensus that colouration in this species was sexually dimorphic, with yellow males and black females. The research station, however, contained several preserved specimens of C. limbatus, including one with a yellow colouration, which appeared to be female based upon its external morphology. Whether this represents an aberration, an immature male, or evidence that the colouration is not truly an indication of sex is not yet clear and will not likely become clear until further specimens can be examined.
Centruroides was not the only genus of scorpion to be found. I was pleasantly surprised to find a great number of beautiful Tityus ocelote. This small species only grows to around 1.25 in [3 cm] and is exceedingly cryptic in its colouration. It would have been exceedingly difficult to find them had I not been using an ultraviolet [UV] light, which causes scorpions to fluoresce. Using my home-built UV light, I was able to determine to some degree the local distribution of this species. Notably absent from the denser forest, T. ocelote appeared to be found only on the large trees near the ocean, around which the undergrowth had been cleared and there was a noticeable breeze. What was even more fascinating is that when one was found on a tree, there were often a half dozen individuals or more sharing that same tree. On other nights, or even later that same night, the trees that had previously shown an abundance of T. ocelote would reveal no specimens. Conversely, trees which had previously been bare would spring to life and a scan with my UV light would reveal numerous specimens from ground level up to three or four meters up the trunks. What factors would lead to this pattern of activity was not clear, nor was it clear where the scorpions disappeared to. One hypothesis is that they ascend higher into the trees at times, finding hiding places among the numerous branches, leaves and vines that cover the external surface of the trees. Regardless, it will take considerably more investigation to reach any sort of definitive conclusion.