Among other things, we wanted to study biodiversity of one group, butterflies, and compare those results to similar studies of other groups -- moths, birds, spiders, and so on. We captured, marked, and released butterflies to get and idea of what species are present, of the density of various species, and of their migration patterns.
Most of the photos here were taken in Wilson Garden, but I had a few other butterfly-related photos from other parts of Costa Rica, so I just tossed them in as well.
There are larger versions available for all of the images. To view them, simply click on the images in this file.
Here's another page of my photos of Costa Rican plants and animals.
Here is Gretchen with her Costa Rican assistant, Yimer, working at a butterfly trap. The traps hang from trees, and are composed of a cylinder of netting closed at the top. About an inch below the bottom of the cylinder is a board upon which is mounted a bait dish.
The bait consists of a mixture of bananas that are way over the hill, molasses, and rum. I think the rum was originally added so that the smell of alcohol would be there immediately, and we wouldn't have to wait for the bananas to begin fermenting spontaneously.
We needn't have worried. In the tropics, the stuff ferments so fast that you've got to take care to open the jar containing the bait regularly or it will explode. One jar did explode in a warm car the first year. Luckily, it was a rental car.
Butterflies are attracted to the bait and fly under the edge of the cylinder. When they're finished eating (and probably half drunk), they almost always fly straight up to leave. Most are too stupid ever to escape.
Since the butterflies are in the top of the trap, it's a simple matter to close the netting in the middle and tie it off, as Yimer is doing in the photo, and then to remove the butterflies one by one through a velcro-closed slit that you can see in the top half of the cylinder. (Well, you can see it in the big version of the photo.)
What makes it a bit exciting is that there are all sorts of other
critters in the trap, and some are more interesting than others. There
were flies, weird beetles, moths, and earwigs, which weren't too bad,
but there were also plenty of bees and hornets. In Costa Rica, almost
any bee you see is an Africanized "killer bee".
After you pull the butterflies out of the trap, you have to figure out what they are, and their sex, if possible. Here's a Smyrna blomfildia being checked out by Yimer. There's a pretty good butterfly book for Costa Rica with color plates which covers most of the families of butterflies we tended to catch. Because of the particular bait we were using, we only caught rotten fruit eating butterflies. In the traps, we'd see the same ones over and over, but there were dozens of other species we'd see fluttering around that were not attracted to the traps at all.
Some butterflies are sexually dimorphic -- the males have different
scale patterns on the wings than females so those sorts were easy to
sex. Sometimes it wasn't wing patterns that differentiated the sexes,
but other obvious structures. But sometimes you had to poke around
gently in the hinderparts of the butterflies to see if they had male
"claspers" or not. That was tough to do in the field, so the accuracy
Each time we pulled a butterfly came out of a trap, we'd check to see if it was already marked. If so, we'd record the mark and the new trap number, and if not, we'd mark the wings as shown in the photo to the left. The "B1" indicates that this is the first butterfly caught in trap B. Marking was done with a felt-tipped pen. The example here was easy to mark -- it's large (this is the Caligo atreus), and it's in good shape. Some of them can be really beat-up, and most of them are smaller to begin with, anyway. (It's also known as an "owl butterfly" because the eye-spots on the wing look something like owl's eyes, and perhaps serve as some protection against predators)
In temperate regions butterflies spend a long time as caterpillars, and when they emerge, they're ready to mate, lay eggs, and die, so they spend only a tiny fraction of their time as butterflies, and most of the time as caterpillars.
In the tropics, it's more dangerous to be a caterpillar and the butterfly form is better able to avoid predators, so many tropical butterflies are not so mature when they emerge, and need to eat more than nectar, and produce a few eggs at a time over a long period.
Those that are around for a long time get chewed on by birds, get the
scales knocked off their feathers, and so on. It was amazing to me to
see how little of the original wing was required to fly in some of the
very old specimens we caught.
Part of what we were studying was the differences in butterfly populations that were found in forested and deforested areas, so we set up traps in primary forest, secondary forest, and in non-forest (cow pastures).
Unfortunately, most of the traps weren't on trails. Worse, lots of them were in primary forest. The problem is that except for in the national parks, Costa Rica has cut down almost all its primary forest. Well, all except the stuff that's in ravines too steep and nasty to get the trees out, so that's where the traps were.
Most of the hiking was through "degraded cow pastures" -- mud and cow shit, choked with waist-high bushes and grass, hidden barbed-wire fences, and teeming with spiders, chiggers, and God knows what other kinds of critters. We had our own colorful geographic names -- "cow ladder", "cow drop-off", and "cow sewer", leading down to "cow cesspool", which had a trap hanging over it.
Our "trails" to the traps were not switchbacked like those that are the pride and joy of the US Forest Service -- they were generally straight lines, and each trap visit converted them more and more into the Costa Rican equivalent of California's water-slide amusement parks. The only difference is that these were much more slippery, were made of mud, and generally didn't land you in a pool of clean, chlorinated water at the end of your slide.
Here's a shot of Scott Daily (Gretchen's brother) up to his hips in "cow
ladder". I didn't dare take my fancy camera down to "cow cesspool", so
you'll have to use your imagination.
Yessica lived in a house near one of the sets of traps we visited.
She's the cutest little girl in the world, and insisted on helping us
when we serviced the traps near her home. She always got a few colones
for her trouble.
Since this is my butterfly page, I figured that shots of caterpillars
also belong here. We found a large leaf (perhaps 8 inches long)
completely covered with these critters. Funny thing though, when I
returned the next day, the leaf wasn't there. I wonder what happened to
The pretty patterns on butterfly wings are produced by tiny colored scales. If you rub a wing, the scales come off -- the scales are the "powder" you get on your hands after handling a butterfly. Without the scales, butterfly wings are pretty much transparent.
Some butterflies do not have any scales on portions of their wings, and
this example only has them around the outside edges. With the mostly
transparent wings, they are very difficult to see as they fly. There's
often just a ghost-like flickering as they go by. I imagine it's pretty
tough for birds to catch them.
This is one species of the famous "Blue Morpho" butterflies. It's large
(perhaps 5 inches from wing tip to wing tip), and it's a beautiful
irridescent blue color. This one's in fairly good condition, but
obviously a bird or something has taken a little chunk out of its left
This photo is not from San Vito, but from the park at Monteverde. I saw a number of caterpillar parades like this one. Each has his eyes next to the butt of the one in front. I've read that there are several species that do this, in the United States, even, but this is the first time I ever saw it.
It seems like a strange strategy -- each one's fate is linked to the
luck of the leader -- but maybe when they're arranged like this the
result looks like a much larger creature which predators might try to
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Tom Davis ( firstname.lastname@example.org)