Day Five

We spent the morning working in the ambient lab, documenting any changes in the caterpillars that had not pupated or became parasitized yet, and after lunch we were given a lecture from Dr. Smilanich on the ecological immunology of diet breadth, or in other words, what ecological and evolutionary processes influence the scope of a caterpillars diet. Out of the countless species of caterpillars found in Central America, most are specialists when it comes to diet as opposed to generalists, and this is due to a number of factors.

From this lecture, I learned that Caterpillars have adapted to prefer certain host plants over others, which in turn serve as defenses from predators and parasitoids through crypsis, and biological sequestration. Crypsis in caterpillars is an anti-predator adaptation, as most caterpillars are able to camouflage themselves within the plants they feed on. Certain chemicals within host plants may also boost a caterpillars immune response to parasitoids through sequestration, which is the ability for organisms to store compounds in their bodies from the plants they ingest, and some of these compounds can potentially repel predators. While it is not fully clear if rates of parasitism are linked to immune strength, and phytochemistry of host plants, it is clear that as host plant diversity increases within a certain species of caterpillar, rates of parasitism increase as well due to decreased immune responses. This was a very interesting lecture, and from it I learned that these tri-trophic interactions between plants, caterpillars, and parasitoids are extremely important, and an imbalance among them could be the result of the decrease in parasitism rates that have been observed on recent years.