Natural History

Observing how species look, behave, and interact in nature is how many of us first become interested in the natural world - and these same observations become fuel for ecological hypotheses. Exploring natural history is one of the best parts of ecological research, and foundational to the Robinson Lab. This page is dedicated to natural history observations made by lab members.

06.09.2023. an Ode to Paleacrita: small but mighty in the California Chaparral

When I started my PhD in 2012, I had great clarity about one thing: I wanted to collect caterpillars. Many caterpillars. The horizontal surfaces in the lab slowly became covered by white-topped vials, with a steady stream of folks passing through to clean frass (caterpillar poop) and take photographs. I was studying shrubs in the California chaparral — plants in the genera Arctostaphylos, Ceanothus, Quercus, and Adenostoma. Adenostoma was my favorite: it blanketed the hillsides of Lake County, and was absolutely gangbusters for caterpillars. The first Adenostoma I whacked with my beating sheet returned 200 tiny caterpillars, all in one go. My dad, who was with me at the time, and I uttered shouts and several expletives and - in the first of the many standard dissertation missteps - I decided each one must be collected. I used a paintbrush to race them to the edge of the canvas sheet, and then squished at least half opening and closing the lid. How is it that such a tiny creature could be so speedy?!

Later, once all those missteps had edged the path that becomes a dissertation, I had gotten to know this species well. My first name for it was “green to brown fade-away geometrid’, so-named for an unusual color transition along its body: a green front half, turning smoothly to a brown rear. Later in their growth as a caterpillar, they took on more uniform coloration, though variable among individuals - from yellowish green to brown to gray, but always with a trademark string of diamonds along their back. I eagerly awaited the arrival of the first adult, which would reveal the fadeaway’s identity. The first one hatched on an early Spring day, crawling from its pupa between layers of paper towel. I thought it was a mutant, as it lacked wings; but would learn that this species has flightless females, a trait that has evolved in several moth lineages. She was an odd creature, with gangly legs and a plump body. The males by contrast were delicate, with long wings. They were both small and muddy-looking - yet my time spent with their wormier form made them remarkable. As caterpillars they were excellent stick mimics, holding their body rigidly when disturbed. They were hyper abundant; in 2016 alone I collected 750 individuals. I wonder if they were a favorite snack for keen-eyed shrubland birds. They were attacked by a fabulous array of parasitoid wasps, from Rogadines that turned them into little mummies, to Eulophids that clustered on their back like bunch of green grapes. By the end of my fieldwork, I could pick them out by eye on a plant; and each one that plopped on the sheet was like seeing an old friend. When I needed an abundant native species for parts of my research, they were an easy choice; I knew their habits well, and was able to use their power in numbers and egg-laying for multiple parts of my PhD - from looking at bird exclusion effects, to measuring larval growth rates on different Adenostoma populations. This was Paleacrita longiciliata: the small but mighty inchworm of the chamise hills. - Moria