Preconceptions dashed by sad faces, black pepper, and purple tomatoes

For our first full day of collecting, Arturo Casasola guided us south of Ixtlán, to the community of Lachatao. The winding mountain road brought us to a pine-oak forest that looks a lot like Canada — until you see the bromeliads decorating the trees. It wasn’t quite wet enough to be a cloud forest, but it had some of the elements — not only the bromeliads, but also many other epiphytes (plants growing on other plants) on the branches of the oaks, especially lichens and mosses.

I brought to this collecting expedition a particular concept of where Mexigonus jumping spiders live: mostly on the litter of dry fallen leaves beneath trees. I had formed this idea from previous collecting of other jumping spiders. As I’d collect Habronattus, one of my favourite groups, on such leaf litter, I’d often find a few Mexigonus along the way.

Given this preconception, when we got to the Lachatao forest, I started looking on the leaf litter, and promptly found a little humble brown and tan Mexigonus species quite common there. Good! I decided to try something bold, to look on leaf litter not on the ground, but accumulated in the crooks of branches of the trees. I found a strange cryptically-coloured Mexigonus and was motivated to keep looking above ground. In the end, the team found this cryptic Mexigonus to be common on the epiphyte-covered branches of the oaks — not the habitat of my preconceptions.

We call this species “triste” (sad) for the melancholy expression on their little faces. Here is a male.

Mexigonus “triste”, male.

It turned out that that wasn’t the only Mexigonus living above ground in the forest. We found a small peppery black species by beating dead branches of trees in shadow. (Beating is a technique we use a lot — we hold a kite-like sheet under a bush or tree and shake or hit it with a stick. For more details see here:

In the end we found two species of Mexigonus on the ground, as I’d expected, but three species beating bushes and trees (sad face, black pepper, and a third that I’ll describe next post: purple tomato). All 5 of the species are most likely new to science. This is a happy way to dash one’s preconceptions.

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