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During our visit to the University of Costa Rica campus, we had some time to explore a small area outside the Biology building. As I’m interested in spiders, I had a look around to see what I could find. Given the incredible biodiversity in Costa Rica, I expected to find a few specimens. However, I found amazing diversity even in the small area we explored. On a single tree, both a hunting spider (Figure 1) and several orb weavers (Figure 2) could be found. It seemed that every structure that could support a web had at least one arachnid resident. One tree even hosted a small aggregation of spiders (Figure 3), which I had never gotten the opportunity to personally see before. The sheer number of species that could be found in a cursory survey was simply astounding.
While I was surprised by the diversity of the spiders in the area, I noticed that despite being thousands of miles away from Kansas, many common traits could be found between spiders from the two regions. While I cannot say with complete certainty without examining specimens under a microscope exactly what genera some of these spiders belonged to, but many showed morphological characteristics that I had seen in field work in Kansas before. Micrathena is a genus of spider that has a carapace with characteristic spikes. A spider with such spikes was living between two of the trees (Figure 4). Another genus, Cyclosa, was likely represented as well (Figure 5). These spiders use parts of prey and plants to decorate their web as camouflage, as can be seen in the attached picture.
Costa Rica has an incredible level of biodiversity and seeing just how many species can be found in an area has been an unforgettable experience. However, recognizing genera of spiders from previous fieldwork has shown me that while not every country can have as diverse of wildlife as Costa Rica has, you can see some pretty amazing animals in your own backyard. - Eric Becker
As I mentioned in my introduction, I am working on my own project in addition to the research we are doing as a group. During our time in Monteverde, I’ll be setting out traps to see if parasitoid wasps in Costa Rica are attracted to a chemical called cantharidin. Cantharidin is a toxic chemical produced by blister beetles and false blister beetles as a defense (Hashimoto & Hayashi). Previous similar experiments captured a few of these wasps, but not nearly enough to definitively establish that some are attracted to cantharidin. At the suggestion of Paul Hanson, a professor studying hymenopterans (ants, bees, and wasps), I started planning an experiment to discover if any could be found.
Earlier in the summer, I set several traps in prairie areas of the KU Field Station, but a cloud forest in Costa Rica is considerably different from the grasslands the traps were originally designed for. A few elements had to be changed from the original trap to be better suited for the new environment. The initial traps were inverted funnel traps made of 2 liter soda bottles with cantharidin-impregnated filter paper as bait. An inverted funnel trap works on the idea that many insects will be able to climb into a hole, but will fly straight up when trying to escape. Having a small hole allows insects to enter, but prevents them from leaving. The bottle was made into a trap by cutting off the top where it starts to curve, then putting it upside down. In both locations, I put alcohol in the bottom of the trap to kill whatever insects landed in the bottom and then preserve them until they could be collected. Traps were attached to a wooden stake with waterproof duct tape to ensure they would stay upright.
The big difference between the traps was how I dealt with the issue of keeping the bait dry. I was told that filter paper holding the bait could not get wet. In Kansas, I focused on minimizing the problems caused by water getting the traps. To keep the bait dry, I suspended it from a wooden dowel put through holes in the side of the trap. With the bait in a safe place, I only had to prevent the trap from flooding. To do this, I made a few holes slightly above where the alcohol was and covered it with mesh to allow any excess liquid, likely rainwater, to drain out. In Costa Rica, I had the opportunity to prevent rain from entering the trap at all. To accomplish this, I made several rain covers using garbage bags, duct tape, and twine. This allowed me to suspend the bait with a strip from a ziplock bag and some tape. The advantage of this method is that I can put the bait directly under the hole in the trap, which makes it more attractive to insects. These traps can be seen in Figure 1.
One thing to note is that with the exception of the bait, all the materials used in the traps can be purchased at a grocery store for a few dollars. Science experiments don’t have to cost a fortune to carry out. A few household products and a little bit of preparation can answer plenty of questions.
Hashimoto, K. and Hayashi, F. (2014) Cantharidin world in nature: a concealed arthropod assemblage with interactions via the terpenoid cantharidin. Entomological Science 17: 388-395.
Image: Insect trap set-up used at all three sites in Costa Rica (Photo credit: Eric Becker)
My name is Eric Becker and I’ll be a senior at the University of Kansas. I’m currently studying organismal biology with an unofficial concentration on entomology with a bit of arachnology. I’m particularly interested in behavioral biology. In addition to the research being conducted as part of the course, I’ll be using this opportunity to work with parasitoid wasps, a group of insects I have an interest in. I plan to compile a list of parasitoid wasps in Costa Rica that are attracted to cantharidin, a toxic substance produced by blister beetles.