Bullhorn Acacias

Bullhorn Acacia (Acacia cornigera)

On my recent trip to Mexico, we saw lots of bullhorn acacias (Acacia cornigera), particularly in the sand dune areas at Cansaburro. They are attractive shrubs that are named for their prominent swollen thorns that resemble a bull's horns.

Yes, the thorns really do resemble a bull's horns.

Bullhorn acacias are noteworthy for their complex, mutualistic relationship with one particular ant species, Pseudomyrmex ferruginea. Most acacia species contain lots of bitter alkaloid compounds in their leaves and stems, which act to deter browsing by various herbivores. Bullhorn acacias lack these chemical defenses, but have lots of biting, stinging ants living on them. The ants hollow out the large thorns and nest in them.

Pseudomyrmex ferruginea

This hollowed-out thorn contained an active ant nest

The mutualistic relationship between the ants and the acacias was studied by biologist Thomas Belt, who described the interaction in his charming 1923 book The Naturalist in Nicaragua. The ants deter herbivores with their painful bites and stings. They also remove seedlings that sprout around the base of the tree, thus eliminating potential competitors for sunlight. In return the trees provide food for the ants. Protein-rich nodules called Beltian bodies form at the tips of newly-unfolding leaves. These are harvested and eaten by the ants.

Pseudomyrmex harvesting Beltian bodies

The acacia trees also provide carbohydrates from foliar nectaries that form at the base of some of the leaves. The ant/acacia relationship has a long evolutionary history, with both partners showing a considerable dependence on one another. Colonies of this species of ant are only found living on acacia bushes. Conversely, acacias that have been experimentally cleared of their ant colonies suffer considerably more herbivory than bushes that retain their ants.

Foliar Nectary

I was a bit surprised at the lackadaisical nature of the acacia ants that I encountered in Veracruz. Shaking the bushes, or even giving them a stiff whack with the handle of my butterfly net only produced a small amount of rather tepid ant activity. I contrast this with my encounter with another ant-protected tree some years ago in Costa Rica. In that case, the tree involved was a cecropia. When I struck the trunk just once with a stick, thousands of tiny ants boiled out of small holes in the bark.

Otros Insectos Mexicanos

Dunas de Cansaburro, San Ysidro, Veracruz

I've been poring over the roughly 750 photos that I took on my Mexican trip. I saw and was able to identify 76 species of butterflies on the trip. I have reasonable photos of 58 species.

The organic farm Cañada el Equimite near Coatepec

I took far fewer photos of dragonflies. That's partly because we saw far fewer species, but also because Celeste did most of the dragonfly photography. She was using the Xerces Society's camera (much better than mine) to take macro photos of hand-held specimens for later identification. We did take a few shots of dragonflies in environmental settings- but that was not our main goal.

B52? Nope, it's an enormous mosquito
Photo: Celeste M.

I did see (and photograph) other types of insects. I also felt a lot of critters. The mosquitoes and biting midges were ferocious. Celeste quipped that they viewed the Off that we were dousing ourselves with more as salsa than as insect repellent. She took a great photo of a huge mosquito that I stunned.

I did get to photograph three groups that I have particular affinity for. We saw a couple of cool band-winged grasshoppers. One with orange wings showed up in a bunch of dry spots with sparse vegetation. One particularly windy day in the dunes, they looked totally sandblasted. I think they might have been Lactista punctatus.

Sandblasted grasshopper at the Cansaburro Dunes

Lactista punctulatus?

At the organic farm up in the highlands we saw numerous examples of Macherocera mexicana, with beautiful bright blue hindwings. This species has recently been found in the US with the discovery of a population at the base of the Rincon Mountains just east of Tucson.

Macherocera mexicana
Photo: Celeste M.

Aren't my blue hindwings beautiful?
Photo: Celeste M.

We saw a couple of cool longhorn beetles. Most notable was this enormous, brightly colored Lissonotus flavocinctus from the Cansaburro Dunes. Thanks to Ted and Mike for help with the ID. There was also a very pretty (not yet identified) species that turned up at the botanical gardens in Coatepec.

Lissonotus flavocinctus

Cerambycid beetle at the botanical gardens outside of Coatepec

We spent quite a bit of time in the coastal dunes near San Ysidro, including the Pronatura reserve called Dunas Cansaburro. It's a beautiful reserve, and many readers have already figured out that this means tiger beetles. Unfortunately I did not get good photos at the dunes. When we were in tiger beetle habitat we were faced with a howling wind and stinging sand. I was able to get a (not very good) photo of Cicindela curvata. We also saw a species that may be C. sedecimpunctata. That turned up in a number of spots that we visited, and I was able to get some better pictures.

A terrible photo of Cicindela curvata

Possibly Cicindela sedecimpunctata

Somewhat unexpectedly were the numerous tigers that I encountered in the ruts of a two-track at the organic farm. They look a lot like C. punctulata. If that ID is correct, they are likely subspecies catherinae.

Possibly Cicindela punctulata catherinae
ID awaiting confirmation

Overall, the butterflies were the stars of this trip, but I was happy with some of the other biological diversity that I managed to see. There were even a few cool critters with backbones!

On the Futility of Questing for Migrating Dragons

I'm back from Mexico. We didn't see any dragonfly migration, however the trip was not wholly unsuccessful. I think that we returned with a much better idea of what it will take to learn more about the phenomenon as it occurs in Mexico.

Monday was a challenging day. We began early in some wetlands about 20 miles north of the city of Veracruz. That's just about where Hurricane Karl made landfall a month ago, and there was still lots of damage visible. We saw fewer dragonflies than butterflies. Normally that would be fine by me, except that this time around I was being paid to find migrating dragonflies and wasn't having much luck. I was particularly enjoying seeing other species in the same genus as the Silver-spotted Skipper. I also found some tiger beetles. I'm pretty sure that they were Western Red-bellied Tigers (Cicindela sedecimpunctata) a species that's very common in the western US.

Karl's Calling Card

Broken Silverdrop (Epargyreus exadeus)

Mexican Tiger Beetle! (Westerm Red-bellied?)

As we were headed off to the next site, I expanded my Spanish vocabulary. Elisa's car began making a dreadful noise and I learned the words freno (brake) and grúa (tow truck). We made it as far as the city of Cardél where we watched a river of migrating raptors from the roof of the big hotel, then had lunch downstairs in the coffee shop. Celeste and I then took the bus back to Xalapa and got some work done at the hotel there while Elisa had her car tended to. Fortunately the car problem was minor (a stone stuck in a wheel assembly). Unfortunately we lost a whole afternoon of field time.

Tuesday we went to an organic farm near the mountain town of Coatepec. There were plenty of dragonflies in the artificial pond, but little species diversity and no migratory activity. Some of the Mexican dragonflies are stunningly beautiful.

Hercules Skimmer (Libellula hercules) at the organic farm

There were lots of butterflies like this Blomfild's Beauty (Smyrna blomfildi)
on rotting fruit at the farm

Glasswing (Episcada salvinia)

Wednesday it was back to the dunes at Cansaburro. Thew weather was marginal, which probably put a stop to any migratory activity. Once again we saw lots of butterflies. Mexico has some amazing and beautiful skippers.

Blue-studded Skipper (Sostrata bifasciata)

Fantastic Skipper (Vettius fantasos)

Thursday was the last day of field work. We were hosted by Eduardo, who is also an employee of Pronatura. We visited the ecological field station at La Mancha, and later wandered along a dirt road where Eduardo sometimes takes visitors bird watching. We saw some very cool dragonflies at the bird watching site, but once again saw no migration activity.

Tropical Dasher (Microthyria sp.) at the field station

It's too bad that our visit did not coincide with obvious dragonfly migration activity. On the other hand, I met a bunch of new colleagues with whom I genuinely enjoyed spending time. I saw a beautiful part of the world and got to photograph lots of species of insects that I have never seen before. I believe that we learned a lot about what it will take to better study dragonfly migration, and look forward to presenting our results in December at a meeting that will take place in Austin, Texas.

Veracruz: Here There Be Dragons

Pico de Orizaba- the view from my hotel window

Saludos de Mexico. I'm in the city of Xalapa in Veracruz. I'm working with the US Forest Service, the Xerces Society and Pronatura to try to figure out how we can include dragonflies in the USFS international migration program. We are visiting a bunch of sites, collecting data and identifying species. The Pronatura folks would also like some butterfly identification for a site that they own, so I'm helping with that as well.

Big-spiked Gemmed Satyr (Cyllopsis pephredo)

Anna's Eighty Eight (Diaethera anna)

I'm staying in the city of Xalapa, and working with my colleagues Elisa who lives in Xalapa and works for Pronatura and Celeste, who lives in Portland and works for the Xerces Society. The afternoon that we arrived, Celeste and I visited the Museo de Anthropologia, then went for a walk in a preserved woodland remnant right in Xalapa. We got some nice butterfly photos.

Welcoming committee at the dune refuge

Large Dune Complex

On Monday we went to a preserve right on the coast. It's a complex of dunes and coastal wetands. Xalapa is famous for its raptor migrations, and we worked out of a Pronatura raptor banding blind. We got to watch some of the ornithologists at work.

Banding a Sharp-shinned Hawk

We've gotten to see lots of cool species of dragonflies, but have yet to encounter migratory swarms. With luck, we'll see some of that before the week is out. Meanwhile, both the dragonfly and butterfly species diversity have been outstanding.

Roseate Skimmer (Orthemis ferruginea)

Malachite (Siproeta stelenes)

Dusted Spurwing (Antigonus erosus)

Pilgrim's Progress

I was at the monarch butterfly reserve at Cerro Pelón in Mexico on Saturday. Predictably, I'm at a loss for words. For those of you who do not know, the generation of monarchs that flies east of the Rockies in late summer migrates to Mexico. This is virtually the entire population from that region. They winter in fir forests high in the mountains west of Mexico City. To date, 12 sites have been discovered, each only tiny area in extent. The butterflies cluster together by the tens of millions. There were estimated to be over 50 million monarchs in Cerro Pelón on Saturday.

Mountains of the Transvolcanic Belt

Wild marigolds

The trip began from the conference hotel in Morelia. We spent the morning driving through the beautiful mountains of the Transvolcanic Belt to get to the sanctuary near the city of Zitácuaro. It was a sunny day that included several photo stops. I enjoyed seeing a variety of blooming plants, including the wild ancestor of cultivated marigolds.

Doug, very much not in his natural habitat

We got to Cerro Pelón and headed up to the sanctuary on horseback. Horses are something that I have absolutely no experience with. I had previously been on a horse exactly once. Someone helped me into the saddle and I sat like a sack of potatoes while the horse walked about 100 yards. Not so this time. We rode for about an hour and fifteen minutes and gained a couple thousand feet in elevation getting up to the grove of trees with the butterflies. I even had to steer. My 8-year old minder was clearly much more adept with horses than I was. Thankfully, he was very patient with me.

Approaching the monarch-covered trees

At last we came to the butterflies. It was a warm sunny day when we arrived, and there was a surprising amount of flight activity. Describing this is impossible. These photos don't even begin to do it justice. When you stand among acres and acres of trees where all of the branches are being weighted down with tens of millions of monarch butterflies, you realize that you are witnessing one of the epic phenomena of nature. We were all spontaneously speaking in hushed voices. A member of our party observed, "it's like being in church." I recall my first visit to a monarch sancuary in 2002. I had the feeling that I was somehow different for having witnessed it- that I had in some way had a religious experience. It was much the same this time. Everyone should see this once before they die. Few ever will.

Monarchs everywhere

Pendulous clusters of roosting monarchs