So, I’ve previously described the tube experiment, which I’ve been running for about a month now. Each tube is filled with detritus and water from the leaf where it sits, and contains larval insects. The larvae are in pairs of (congeneric!) species wherein one is a generalist on all bromeliad sizes, the other found only in the largest plants. If there is anything in the environment provided by large bromeliads that makes the specialist succeed over the generalist, then this experiment should pick up that difference.
The larvae in the tubes eat the detritus, experience the environment, and, if they do well there, eventually pupate and emerge as adults. When necessary, there’s a little popsicle stick there for them to crawl up to freedom.
Of course freedom, in this case, is a net bag where they wait for me to collect them with my aspirator! The taxa of these bromeliad animals are poorly known, and there was just no way to identify the adults positively when they were still alive. So, I’ve been catching every adult chironomid that emerges, killing them, and preserving them in eppendorfs atop some silica and cotton. So far I have well over 150!
It’s strange the skills you acquire as a field biologist. I spend at least an hour a day at this task, and over the last month I’ve gotten pretty good at deftly slipping the mesh top off and seizing the insect with my aspirator. I’ve also become embarrassingly attached to this particular tool of the trade, which I made myself from a description by Karen Needham, the entomology curator at the Beaty Biodiversity Museum.
The routine of checking the tubes is a classic field-biologist repetitive task. Most of the tubes are empty, but each has to be checked every day, and maintained carefully (did you know that ants love to eat mesh and elastics? I was surprised, too). Emergences are exciting — they mean data, and are especially essential in the two-species tubes which test for competitive differences. Emergences are also a trial, and mean that the collecting trip will be prolonged while I catch the insect. On big days (once there was 16 in a single day!) the whole collecting can take close to two hours, and my field assistant would let out a shout of “NOSSA!” (the Brazilian equivalent of “jeez!”) at every fresh discovery of an insect.
Someday soon I mean to sit down with the adults and try to work out if the guesses I’ve been making all along about species identifications of adults are actually accurate. Fortunately I have lots of monoculture insects to learn from. I’ll study them, and then see how I can do with the polyculture insects! We’ll see, and I’ll let you know what I find!